"The most merciful thing in the world, I think, is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity, and it was not meant that we should voyage far. The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the light into the peace and safety of a new dark age."
YuYu Hakusho of all series has this happen to Sensui in his backstory. Not from any eldritch lore But from simply seeing how horrible people can be — shattering his belief in black and white morality by witnessing the torments sadistic humans inflicted on demons for fun, leaving him an omnicidal maniac.. Chapter Black is also noted to be able to force people to go mad from the revelation and it's contents aren't supernatural. Just a compilation of every terrible thing humanity has ever done in loving detail.
What happened to Kurumi's friend Kaafai from Haou Airen when he's Forced to Watch as Hakuron rapes Kurumi. This is why he shoots Hakuron to death in the end.
Towards the end of Neon Genesis Evangelion, Shinji Ikari finds out that Rei Ayanami, one of his closest confidants, has died and been replaced by a clone, and later still he deduces that there is definitely a connection between her, his dead mother, and the weird presence in Eva Unit 01, and these revelations does indeed shake his already fragile psychological stability quite a bit. It finally comes to a head in The End of Evangelion when the ritual to awaken Lilith/Rei Ayanami reduces him to a fit of shrieking omnicidal insanity. It didn't help that he had just seen Asuka's torn-apart remains only about a minute earlier.
More or less every single Tipharian in Battle Angel Alita that learns "the secret of Tiphares" (Tipharians undergo a special ceremony at the age of nineteen. During this ceremony, the brain of the Tipharian is replaced with a computer chip) is driven insane. Most commit suicide.
Alita is a citizen of Tiphares thanks to Desty Nova. Heroic BSOD time!
The events of the Eclipse in Berserk took a horrible toll on the mind of Casca, who not only lost every one of her men, including Judeau, to things out of nightmare, but was raped by the very essence of evil itself in the form of the fifth member of the Godhand, Femto — who used to be Griffith, one of the two most important men in her life — right in front of Guts, the man she loved. The trauma of the experience rendered her mute, amnesiac and insane, and it was not helped one bit by Guts leaving her for two years to pursue vengeance against Griffith.
In Fantastic Children, scientist Dr. Radcliffe became obsessed with unraveling the mystery of the Children of Befort. Needless to say, the more he found out, the madder he went. He could have been saved a lot of suffering if he knew that his theory was actually as far from the truth as you could get.
Space Pirate Mito: Masatsuki Nenga goes insane when he comes to the realisation that his "Justice" is nothing more than a tool of oppression (one that has no issue shooting down a "mob" of villagers, men, women and children) used by a pretender to the throne. This leads to about two episodes worth of him screaming "I AM JUSTICE!" at the top of his lungs whilst firing his gun like the lunatic he is. This would be fine all in all, but the guy doesn't look older than 12.
Notably, if you didn't already know who was going to grow up to be the villain, it would look like Knives handled it better than Vash. They both locked themselves in and attempted to starve to death together, but after Rem broke in and saved them it was Vash who did the Creepy Laugh and Humans Are Bastards and hysteria, and Knives seemed...perfectly okay. He saved his freak-out until after he'd set up all the colony ships to crash.
Digimon Adventure 02: Certainly not the only factor in his descent, but his visit to the Dark Ocean a perpetually dark realm, populated by various Lovecraftian horrors and where Love and Hope are a foreign concept, was definitely the Straw that Broke the Camel's Back for Ken Ichijoji. One look at his expression◊ in that scene is enough to convince you that this kid just went off the deep end.
On Moonphase, Kouhei experiences temporary madness after his new power lets him see Hazuki's true form, after which he temporarily becomes a trembling wreck who screams like a madman every time he sees her, he eventually gets over it though.
in 20th Century Boys, approximately 2/3 of the people who complete Friend's VR, which purportedly reveals his face, are Driven to Suicide. It's not his face, it's Sadakiyo's—specifically it's his adult face on a child's body. In a simulation that is otherwise completely indistinguishable from reality, it drives people crazy simply because of how wrong it looks.
Towards the end of Gankutsuou Heloďse Villefort, who seems perfectly normal in her first appearances, is revealed to actually be a murderous woman who's out of touch with reality. When her husband tells her to her face that she's just a murderous Bitch in Sheep's Clothing, and reveals that he knows she's been trying to kill him and their daughter Heloise collapses to the floor, finally giving into her insanity. Her husband then has her committed to an insane asylum for the rest of her life.
Perfect Blue: In the anime's denouement, Rumi is permanently delusional and institutionalized.
Occurs to one of the astronomers in Hellstar Remina when he realizes that Remina's a sentient Planet Eater...and it's headed for Earth.
Russia from Axis Powers Hetalia during the Bloody Sunday strip, in which he snaps and starts to mow down his own people on the grounds that "they're not really Russians if they don't love me."
In the Halo Legends segment Homecoming a few of the escaped Spartans find out they've been replaced with clones leading a few to commit suicide.
Happens to Sayaka Miki, and Mami Tomoe from the third alternate timeline in Puella Magi Madoka Magica. Sayaka starts losing it as she realizes that No Good Deed Goes Unpunished, and ends up becoming the witch known as Oktavia Von Seckendorff since she brought hope to others only to lose herself to despair; the third Mami goes insane with grief after the Sayaka of her continuity also becomes Oktavia and is killed by Homura, since she cannot handle the Awful Truth that being a Puella Magi means she will eventually become a witch; she kills Kyouko and gets ready to kill Homura, so Madoka has to Mercy Kill her.
And in the backstory of Kyoko Sakura, this happened to her father, when he found out that Kyoko used her Selfless Wish to brainwash people into following him. His mind splintered so badly that he went the Pater Familicide route, with Kyoko as the Sole Survivor of the Sakura clan.
In Fullmetal Alchemist, it's strongly implied, and possibly outright stated, that the experience of going through the Gate is so "awful" that even if you did manage to survive through the pain of whatever it took from you, you could wind up a vegetable.
Issac McDougal AKA The Freezing Alchemist from Episode 1 of Brotherhood went totally off his rocker when he uncovered the country wide transmutation circle conspiracy, and decided to remedy the problem by attempting to reduce Central to a frozen pile of rubble.
Jeremy has one of these in A Cruel God Reigns after he finds his mother's diary detailing that she knew Greg was raping Jeremy, but did nothing. This leads to his Driven to SuicideBungled Suicide just as he is going to confess to killing Greg to Ian.
Mewtwo from Pokémon: The First Movie goes off his gourd when he's basically told that his purpose in life is just to be a science experiment and/or a weapon and nothing more to those who created him. As a result, he psychically nukes a lab and a Team Rocket base, kills the scientists who brought him into being, almost kills Giovanni, and decides to make himself judge, jury and executioner to every human and Pokémon on the planet. Ash's desperate attempt to stop the fighting between the clones and original Pokémon is enough to bring Mewtwo back to Earth and question his initial belief on humans.
Naruto: Sasuke, understandably, did not react well when he found out the truth about Itachi. Thankfully, after 200 or so chapters, he got better.
In Rurouni Kenshin Soujiro goes temporarily insane when he realizes that he did regret killing people despite clinging to the words of his Evil Mentor: -> If you're strong you live. If you're weak. you die. It doesn't help that the people he regretted killing were his Abusive Parents or that he'd been a Stepford Smiler so long that every other emotion was completely suppressed until then. To top it all off it was Kenshin's words that caused this. It eventually leads to Soujiro's Villainous BSOD.
Invisible Games has this happen at least twice. In Killswitch a man acquires what may be the last surviving copy of the titular video game and promises to upload online videos of his playthrough. The only video he ever posts is of him staring at the camera and crying while the game runs on a screen in the background. Later, in The Pentintytär Arcade, after discovering the scene of a woman's suicide a young boy begins to play the set of unique video games she had constructed. The story that spans across the games haunts him for the rest of his life and drives him to relentlessly collect the games years after the set has been broken up and acquired by different collectors. He is last seen sitting naked among the game cabinets, crying and clutching a gun.
Delirium: Do you know why I stopped being Delight, my brother? I do. There are things not in your book. There are paths outside this garden. You would do well to remember that.
The Joker is like this at least some portrayals, more so than most Batman villains. More than one interpretation (including the 1989 movie) has shown him bursting into maniacal laughter after seeing his chemically-disfigured reflection for the first time. His fellow Rogues Gallery members are listed alongside him under Freak Out.
For instance, The Killing Joke. Averted by Commissioner Gordon's resistance to Joker's attempts to drive him crazy in the same graphic novel.
Then we have the Joker from Flashpoint: Martha Wayne watched her son Bruce die before her and was so overcome with grief, she snapped. She snapped even worse when her husband, Thomas Wayne, revealed that, in another timeline, he'd be Batman, not Thomas.
The Comedian appears to go medium-mad when he stumbles on the secret island prior to the events of Watchmen, although his behaviour (breaking in to the home of an ex-villain whom "he knew wouldn't understand," weeping uncontrollably, and expressing remorse for all the horrible things he's done which nonetheless pale in comparison to the plot he's uncovered) may be attributable more to a massive attack of conscience and ethical sensitivity, thus arguably making him more, not less, sane. A more straightforward example from this work would be Rorschach's Despair Event Horizon, upon discovery of a little girl's butchered remains, which transforms him from a relatively rational crimefighter into a pathologically obsessed Nietzsche Wannabe intent on imposing his own brutal, uncompromising justice on what he sees as an uncaring, meaningless world.
Dr Manhattan also deserves a mention, having been through something very like the Total Perspective Vortex and then acquired the power of God. He doesn't exactly go mad, but he certainly wasn't the same person after his experience.
Enigma features a villain called The Truth who has the ability to look someone in the eyes and remove all the comforting lies they tell themselves. It generally results in either suicide or mass murder.
Cy has had the dubious honour of Going Mad From The Revelation twice in the same series. The first bout of insanity occurs when Nyarlathotep whispers his true name in his ear; after spending the rest of the evening and the next morning in shock, and attempting to commit suicide, Cy finally descends into catatonia for the next year. The second time is some time after Cy's recovery, when he manages to save the world by sending Nyarlathotep back to the court of Azathoth; unfortunately, he manages to catch a glimpse of its main occupant. Cy doesn't survive this next brush with insanity.
In Captain Britain, the precognitive Cobweb goes mad when she makes the mistake of looking into the very near future, which has just been invaded by a cybernetic nightmare from another dimension and is steadily being dominated by an insane reality-warping Prime Minister by the name of Mad Jim Jaspers. Naturally, after puking her guts out and mumbling a few garbled prophecies, she tries to swallow her tongue.
Captain Britain himself had his own brush with this trope when he was first confronted with a supernatural occurrence he couldn't dismiss or explain away - in this case, extradimensional beings contacting him in the middle of a Trans-Atlantic flight. He promptly freaked out and jumped out of the plane. At this point in time, Brian got his powers from an amulet and scepter given to him by Merlin and Arthur. (Yes, them). This has been retconned at some point to Brian getting his brains rattled by a psychic attack and jumping to protect the plane's passengers (At this point he couldn't fly yet).
According to Shattered GlassOptimus Prime's bio, he discovered something so shocking from Cybertron's past that it made him to go insane, and to the present day no one knows what it was he found.
One issue of Hellblazer features a Well-Intentioned Extremist priest who gets into the habit of calling the police when teenagers start confessing their misdeeds to him- and at one point, he goes so far as to physically assault a girl who confessed to having sex with her brother. And then the Devil shows up; after letting him know how badly the teenagers have suffered, he ushers the priest back into the confessional and lets him hear his confession. Minutes later, the priest burns the church to the ground; from then on, he's straight-up Ax-Crazy, murdering people from one end of the country to the next, culminating in his attempt to rape a young John Constantine- which results in him getting a razorblade wedged in his face, being arrested, and committed to an asylum. After being released over twenty years later, he bumps into Constantine again at a local church; by now completely lucid, he explains everything, then jams a pencil in either eye and headbutts the pew in front of him.
John himself was pretty horribly traumatized by what happened in Newcastle in '79, and had to go in and out of institutions for several years afterword.
Prior to this, in Swamp Thing Constantine leads a mentalist to make contact with heroes and villains battling what appears to be a giant, black shelled mollusk that even defeats the Spectre, implied to be an aspect of God. Though the entire experience has been traumatic, Constantine's patsy gets a good look at the shell on the creature to snap his mind: It's not a shell, it's a fingernail. The entire battle had been fought on a scale so alien, whole armies had been assaulting just the fingertip of their foe without realizing.
An issue of Marvel's "What If?" ends with Rogue (after killing Mr. Sinister) discovering the ULTIMATE TRUTH behind the Marvel Universe. The last picture of said issue has her (looking quite rattled and/or mentally shattered, take your pick) sitting down amidst a handful of Marvel comic books strewn around the ground.
Much of the plot of TRON: Ghost in the Machine runs on this trope. The story opens with the protagonist of the game being so paralyzed by what he saw inside the computer system that he went from being an avid programmer to being a shut-in afraid to touch electronics. From there, the whole comic spirals into a genuine Mind Screw.
Human Torch: I traveled through worlds so big...so big...there..there aren't words..! We're like ants..just ants..ants..!
In All-Star SupermanLex Luthor acquires all of Superman's powers. All of them. In the end, he is stopped not by anyone, but Superman's Super Senses. Luthor sees the universe as Superman does and realizes that Superman isn't a villain - his altruism comes from his understanding of how interconnected the universe is. Luther went sane from the revelation!
If you think Humongous Mecha can't have an Eldritch Abomination of their own, you'd be wrong. The original Marvel run of The Transformers featured Unicron, a Planet Eater and Physical Goddisguised as a giant robotic planet. His appearance in that run of the comics causes Brainstorm, an otherwise quiet, sensible, and reasonable Autobot who is looked up to by the others as a paragon of forethought and planning, to utterly lose his shit and simply start babbling a Rapid-Fire "No!" while trying to shoot the planet sized monstrosity with a dinky laser pistol. It doesn't end well for him. For comparison, it's a bit like if you were suddenly attacked by Satan if he were the size of the Earth; the realization that the threat is real and the monster has a form far outside what you were ready to deal with could break even the most level headed individual.
And then it happens to Shockwave, as well, who for the first time ever can't figure out what he's seeing, and just stands and stares at what's happening. He has to rely on Starscream for help.
In the setting of the Mass Effect fanfic Inglorious Boshtets, this is what happened to many people who viewed the porno magazine Fornax's "Forbidden Issue," which featured Tali's idiot crewman Prazza performing a sanity-blastingly obscene sex act that thankfully remainedundescribed.
Occasionally a character in The Infinite Loops will completely freak out when they realize what's happening. This is known as Sakura Syndrome in-universe, due to Sakura being the first known case of it happening.
The typical fate of those who hear the voice of Dark Tails in Sonic X: Dark Chaos. Not only does it drive several individual characters like numerous Marmolins or Venus the Seedrian and Trinity to gibbering madness, it's mind-blasting enough to cause entire space fleets to go insane and destroy themselves.
It's later implied to be the reason for the Liege Maximo's Start of Darkness as well.
Film - Animation
Toy Story — Buzz Lightyear ends up doing this after discovering he is indeed only a toy and not an Intergalactic Space Ranger as he previously believed. He snaps out of it later, though.
And in Toy Story 3, Lotso endures a long and grueling journey back to Daisy's house, only to discover that he had been replaced. As Chuckles puts it, "Something changed inside him that day. Something snapped."
In Frozen, Elsa fled her kingdom Arendelle and built her own ice palace on a distant mountain, mistakenly believing that Arendelle would be safe from her dangerous power. When Anna delivers the news that Elsa in fact unleashed an eternal winter, Elsa is sent into a flurry of panic that leads her to freeze Anna's heart.
Film - Live Action
In Oldboy Oh Dae-su discovers the girl he had sex with was his daughter, madness and cutting out his tongue followed.
In Indiana Jones and the Kingdom of the Crystal Skull, the Crystal Skull itself contains immense psychic power and knowledge, which turns Harold Oxley into a gibbering lunatic and almost Indiana Jones as well. Though he regains his sanity once the skull is returned to Akator.
The Aliens at the climax also have incredible knowledge, which reduces the knowledge-hungry Soviet agent, Irina Spalko, to madness and then dust .
In Dark City, detective Eddie Walenski is driven mad by the revelation that the City and everyone's identity is being mercilessly torn apart and remade by aliens, repeatedly. He compulsively draws spiral shapes on the walls of his room, refuses to acknowledge his wife's identity, and rounds off the evening by jumping in front of a train.
During the ending of In the Mouth of Madness, after witnessing the collapse of human civilization in a rising tide of madness and mutation, John Trent cracks when he discovers that the nightmarish book that did the deed was just a novelisation of everything he did in the last few days. He finds this out by watching the film adaptation.
The Fourth Mistress in the movie Raise the Red Lantern was pushed over the edge when she saw the dead body of the Third Mistress after her execution.
In the Slasher MovieTerror Train, poor Kenny finds out his designated "date" for the evening sitting in the bed is actually a corpse set there by his med schooler "friends". It drives him insane, leading him to get institutionalized and returning after couple of years to exact revenge upon everyone involved.
Parodied in National Lampoon's Class Reunion, in which the Ax-Crazy Walter got that way when he was set up for a masked tryst by his classmates, only to discover that the girl they'd recruited to hook up with him was his own twin sister.
Bram Stokers Dracula: Keanu Reeves' Jon Harker seems to have an episode of this when Dracula feeds his brides. He gets better.
The entire point of the movie 'π' is that this happens when you try to find the ratio that rationalizes pi, predicts the stock market, and is also the true name of God.
Jack Nicholson's Joker loses his mind the instant he sees his new perma-grin in the 1989 Batman movie, stumbling into the street giggling insanely.
Loki from the new film Thor after discovering he is a Frost Giant. While he was already a bit unstable to start with having allowed a few Frost Giants into Asgard for "a bit of fun" (and to discredit Thor), this was what truly tips him over the edge.
When the mummified corpse of Imhotep comes back to life in original The Mummy (1932), the archeologist who saw it went insane.
"He went for a little walk! You should have seen his face! HAHAHAHA!"
This trope, mixed with Hyperspace Is a Scary Place, is essentially the plot of Event Horizon. The test run of the titular ship's hyperdrive sent it beyond the edge of the universe where the crew experienced something that can only be described as Hell. When the rescue crew watches the video logs on the now deserted ship after it returned from the journey they see the former crew engaging in various deranged acts of graphic self-mutilation after the madness of the place took them over.
Implied with Father Brennan in The Omen. It turns out he was a former follower of Satan who freaked after witnessing Damien's birth. When Robert Thorn and Keith Jennings go to Brennan's residence, they find the walls plastered with crucifixes, pages of the Bible and other religious artifacts.
Creepshow. After watching two people get eaten by the thing in "The Crate," Dex Stanley raves and giggles when he appears at Henry's house. He gets better.
In The Matrix, Morpheus suggested that adults freed from the Matrix have an exceptionally hard time adjusting to the real world, why is why they normally don't free people after they reach a certain age. A character remarked "We're gonna kill him. You understand that?" and "He's gonna pop!" on two different occasions regarding Neo reeling from The Reveal.
The Gone series: When she meets the Darkness in Plague, Brittany goes mad and comes to believe that it is God.
The Restaurant at the End of the Universe has the Total Perspective Vortex, which did this to its first subject. It's believed that this will happen to anyone; the Vortex allows someone to comprehend just how significant they are in the vastness of the universe (they become hopelessly incapable of functioning when the answer turns out to be "not at all").
In an episode of the radio series, Marvin the Paranoid Android keeps a couple of minor adversaries occupied by tying them up and playing a recording of his autobiography. They start gibbering and raving.
And getting a glimpse of the universe as it looks through Marvin's eyes is certainly never a good thing. In the first book, a ship's sentient computer responds to a direct link into Marvin's brain by committing suicide. In Life The Universe And Everything, billions of genocidal battle robots are gradually paralyzed by despair when Marvin's forcibly linked into the defense grid. In the movie, Marvin uses the "point of view gun" to telepathically project his perspective onto an attacking army of Vogons. The weeping Vogons have to be picked up by health workers and carted off in a fleet of trucks.
And then there's Prak, whose brief scene is a Parody of this trope. Near the end of Life, the Universe and Everything, an overdose of truth serum causes Prak to tell "the truth, the whole truth and nothing but the truth" about the entire universe, and drives everyone who hears it mad. However, what he has to say is much briefer than everyone expects, and apparently frogs and Arthur Dent are very important to the universe. Prak himself dies after several days of uncontrollable laughter upon meeting Arthur Dent.
When the people of the planet Krikkit discover that there is a universe beyond their home nebula in Life, the Universe, and Everything they can't cope with the revelation and collectively decide that the universe must be destroyed.
The Krikkiters are a special case, as the 'nebula' that surrounded their star system was actually an ancient, malevolent AI that was trying to get them to destroy the universe.
Spider Robinson's novel Telempath involves a virus which multiplies the human sense of smell a thousandfold. It is estimated that one third of the population goes mad or commits suicide due to the olfactory overload.
In the revised first book of The Dark Tower series, a man comes Back from the Dead and claims to have knowledge of the afterlife. When he tells Roland's girlfriend what it is, she begs Roland to kill her. He does.
Sex with recurring villain Randall Flagg in his true form in The Stand makes Nadine Cross catatonic. By comparison, the narration mentions in passing that sex with him in his human form is "only" as traumatizing to his partners as sex with a dog or horse.
In The Wheel of Time, the test for becoming a chief of the Aiel — a desert warrior society with elaborate honor customs — involves passing through an artifact that causes them to relive key moments across thousands of years that led to their formation. Aiel are such a prideful people that the shameful truth of their origins (being descended from those outcast from a tribe of extreme pacifists) hits hard. Rand enters at the same time as an Aiel, and by the end that man is clawing out his own eyes. Rand has a rather unfair advantage here, since he wasn't raised as an Aiel. Rand later reveals the truth to everyone, and hordes begin to defect from the old warrior lifestyle every day, either vanishing altogether, joining a rogue tribe, or taking up a pacifist slave life.
Seen again later with the Seanchan. Their culture believes that women who can use magic are far too dangerous to go free, but also too useful to kill... so they slap collars on them which utterly enslave their wearer and make them puppets to a master, called a sul'dam. Recently, the main characters have disovered that the collars can't be used by anyone who does not have some degree of magical prowess themselves... meaning the sul'dam are essentially the same as the women they treat as objects. When one sul'dam discovers this she undegroes a borderline mental breakdown, and it's speculated that if this knowledge got out publically, it would shake the very foundations of the Seanchan Empire.
In Darkness Visible ordinary people can go mad when exposed to unreality. As things deteriorate this eventually happens to something like a quarter of London's population.
In Kurt Vonnegut's Breakfast of Champions, Dwayne Hoover goes on a rampage after reading a solipsistic novel by Kilgore Trout which says that its reader is the only human being in the world and that everyone else is a machine.
Although it's made clear that Hoover had already gone quite mad by this point, and it's this pre-existing mental condition that makes him believe Trout's book to be a personal message from God.
He couldn't help it; he had bad chemicals in his brain.
The Demu from The Demu Trilogy have their species-wide psychosis because they can't cope with their rite of passage revelation that they are descended from a species that were pets of Neglectful Precursors.
In the second and third Firekeeper novels, the Healed One, ruler of the nation of New Kelvin, is the one person able to read a book that details the true history of their people. The secrets therein driven more than one newly ascended Healed One mad.
In Ayn Rand's Atlas Shrugged, James Taggart goes insane, becoming permanently catatonic, when he finally recognizes his own desire to destroy for the sake of destruction. He, in turn, previously revealed to Cherryl Taggart the monstrosity of his world, beating Cherryl, and cheating on her in the same night, driving her to see what had happened to the world, and resulting in severe psychotic episode. This leads to (possibly accidental) suicide.
In Larry Niven's Draco Tavern story "The Subject Is Closed", one of the tavern's visitors describes how one alien race claimed to have discovered the truth about the afterlife. This is the last that was heard from them, and visitors to their world discovered that they had systematically committed mass suicide. It was later decided to destroy the detailed records of what was found, because those who studied them too closely also committed suicide.
Occurs on a global scale in Lovecraft's short story "Nyarlathotep", which tells of one man (although he's really a messenger for the god of chaos) revealing such cosmic secrets that entire cities are driven mad and civilisation collapses.
In William Tenn's story Firewater, humanity is being observed by aliens that appear to have god-like powers, and anyone who tries too hard to understand them goes insane. Near the end, it's revealed that the aliens have a similar problem with understanding humans.
The Bishop Murder Case: Philo Vance posits that someone went mad from studying quantum psychics.
In Edgar Rice Burroughs's Chessman of Mars, this is claimed for looking on the face of the dead O-Mai, a jeddak said to have died without showing a mark, and whose body was said to lie in a haunted room.
In the Warhammer 40,000 novel Grey Knights, Balurian Imperial Guardsmen are driven out of their minds by seeing the tomb of Saint Evisser. Some "saw a world of glory and bounty" and ran blindly into it only to fall into pits or be attacked by cultists, some collapsed and others struck at comrades in the conviction that all around them were corrupt.
Warrior Cats: Having already developed a near-crazy obsession with the Warrior Code, the realization that her parents were in fact Leafpool and Crowfeather and her very existence was "breaking the code" pretty did away with what was left of Hollyleaf's sanity at the end of Power of Three.
Also, in The Original Series finding out that Tigerclaw is indeed evil, just like Fireheart was trying to tell her all along, pushes Bluestar over the edge for several books.
Invoked a lot in Simon R. Green's Nightside novels. One book features Madman, a former theoretical physicist who'd worked out the means to observe reality as it truly exists; his name says it all. In another incident, a minor character asked the animated corpse Dead Boy what it was like being dead, and was reduced to quivering catatonia by the reply.
In Chris Wooding's novel Poison, the titular character gives up all desire to live after discovering that not only is she a fictional character who was created by the 'hierophant' — a God-like being in the book's universe, and that her home did not exist before she came into being, but that said hierophant has been controlling her all her life, making her choose certain courses of action and make certain decisions. Luckily, she gets over it after discovering that her death would mean the death of those around her, as the story she is in is centred entirely around her.
Which was given a modern film remake by John Carpenter as Cigarette Burns.
In the chapter "The Castaway" in Hermann Melville's Moby-Dick, the cabin boy Pip falls overboard and the immense emptiness of the ocean drives him mad. "By the merest chance the ship itself at last rescued him; but from that hour the little negro went about the deck an idiot; such, at least, they said he was. The sea had jeeringly kept his finite body up, but drowned the infinite of his soul."
Parodied and Inverted in Don Quixote, who goes mad for trying to make sense of the purple prose that plagued the chivalry books he has read, but never was any reveal because even Aristotle could not make sense of that. Chapter I, Part I:
William Gibson's short story "Hinterlands" has a parade of lone astronauts drifting at a particular point in space, setting off radio flares, who are either taken by some force, or more often, not taken. Those who are taken come back with scary new science and technology, but are all batshit crazy and almost all eventually kill themselves without revealing much of what they saw. Those who are not taken are so profoundly crushed at being rejected by Space God that they all attempt suicide, and are then employed as counselors for those batshit crazy returnees.
Here I have lain for so many centuries, to awaken each night at sunset and hold my court as of yore, with specters drawn from the shadows of the past. Man, if you would not view that which will blast your soul for ever, get hence quickly! I command you! Go!”
The Master boasts of this:
It would blast your soul to hear from what far realm I summoned them and from what doom I guard them with ensorcelled crystal and golden serpents.
Their iron nerves had withstood an ordeal that might have driven weaker men mad. He knew it was with no weaklings that he conspired, but men whose courage was as profound as their lawless ambitions and capacity for evil.
The Oculus from the Fablehaven series has this effect.
Revelations are relative: the society depicted in Isaac Asimov's Nightfall lives on a planet with six suns, and its members are greatly unnerved by prolonged darkness. They're about to have their first full eclipse in two thousand years. Things get bad. (It's implied this has happened at least seven times before, each time leaving a few survivors who rebuild from a preindustrial technology level.)
The actual sanity-shattering revelation is how vastly larger the universe (or even the immediate stellar neighborhood) is than they'd ever imagined, and how tiny and insignificant they and their world are by comparison.
A similar theme appears in Douglas Adams' Life, the Universe, and Everything, although in this case instead of breaking down in despair the aliens in question decide that they will "solve" the problem by becoming Omnicidal Maniacs and destroying the rest of the universe.
To quote the text: "Aton, somewhere, was crying, whimpering horribly like a terribly frightened child. 'Stars — all the Stars — we didn't know at all. We didn't know anything. We thought six stars in a universe is something the Stars didn't notice is Darkness forever and ever and ever and the walls are breaking in and we didn't know we couldn't know and anything —'"
I know secrets that would blast even your brain, Bran, should I speak them.
In Salman Rushdie's The Enchantress of Florence, Niccolň Machiavelli met a slave-girl who was transformed by potent hypnosis to be a "memory palace," a kind of exotic hard disk drive. Machiavelli then attempted to restore the girl to a human state, but when she did, she remembered all the perils of her life and defenestrated herself.
In The Dresden Files' Turn Coat, Dresden barely manages to avoid this after looking upon the skinwalker with his wizardly Sight. When he Sees it, he blacks out, only to awaken some time later as a gibbering, incoherent mess, and in physical pain. He recites prime numbers to prevent himself from remembering it for a time. It takes locking himself in a room and assaulting his mind with the image over and over again to get his mind straight (he also gets a Psychic Nosebleed). Even then, he'll never forget what he saw.
The Bookof All Hours by Hal Duncan: several instances it seems. The first is the realization that Thomas Messenger is destined to die, again and again throughout the infinite multiverse of the Vellum, sparking Jack's effort to find the one reality where the man he loves defies the rules and lives. Another has to do with the backstory that contributed to starting the whole story in the first place: one of the reasons the Unkin that joined Metatron's Covenant to fight the Sovereigns was because of the realization that there is in fact no judeo-christian God. Imagine being a believer, undergoing the event of touching the Vellum underneath reality (thus thinking you've been "chosen" or something), and finding out that in eternity dwells... nothing. Just some other humans that, like you, managed to touch the multiverse under reality. One of the biggest is the idea of the Unkin trying to build Heaven in the Vellum - trying to build a tiny, insignificant outpost of crude meta-human order amid the vast, hostile wilderness of eternity that exists beneath the multiverse.
In Fred Hoyle's The Black Cloud, one of the astronomers goes insane from The Cloud uploading its knowledge upon him.
Kurtz in Heart of Darkness, although nothing supernatural actually happens to him. Alone with a savage tribe and faced with the primordial immensity of the jungle, he goes native in the worst sort of way, sets himself up as some kind of god, and descends into acts of brutality left unnamed.
In A Song of Ice and Fire, the Red Wedding drives Catelyn Stark completely insane. As death approaches her, she laughs madly as she claws at her own face.
I seem to have been afflicted with some unprecedented calm, something that settled over me while I was upstairs and which shows no signs of abating. Again, I know we're running counter to the received wisdom, in which our heroine, having glimpsed some unspeakable atrocity, parts ways with her sanity (at least for a time) and runs screaming into the night. Perhaps it's only that those sorts of books and movies are, too often, made by people who have never, themselves, stood at this threshold. Even Catherine ran screaming, that sunstroke day at Cabeza de Lobo. Couldn't I at least be as weak as poor Catherine?
In Bird Box those who view the mysterious creatures outside are driven insane.
Live Action TV
In Smallville, The Helmet of Nabu reveals the fate of everyone to the wearer and drives them insane.
Firefly both pokes fun at this trope and plays it straight. One theory on the Reavers is that were men who were driven insane by seeing the edge of space. Not only is this theory eventually shown to be wrong, but Jayne is immediately puzzled: he's been out there, and it just looks like more space. However, at one point the Reavers intentionally induce Reaver-like insanity in one victim by killing the rest of his shipmates while he is Forced to Watch. The Movie reveals that at least part of River's psychosis was the result of learning what happened on Miranda.
Learning about it subconsciously. Once she had conscious knowledge of it, she got noticeably better. Which isn't to say it made her sane.
In Star Trek, having sex with a Deltan makes one go mad. Or so we've heard. More precisely, the sex is apparently so good that Terrans, at least, have trouble coping afterwards, unless they're Captain James Tiberius Kirk. Then the sex was sorta 'meh'.
The Original Series episode "Is There In Truth No Beauty?" revolves around Kollos, an ambassador of the Medusan race, whose physical appearance is so hideous - or maybe so beautiful - that any humanoid who looks at them directly goes insane. Kollos, in contrast with Shoggoths and Eldritch horrors, is clearly a good guy.
From "The Alternative Factor", Matter!Lazarus goes stark raving mad upon learning of the existence of his Anti-Matter double and becomes hellbent on destroying him, even if it means the destruction of both universes.
In the Doctor Who episode "The Sound Of Drums", we learn that every Time Lord is forced at the age of eight to stare at a gap in the fabric of reality. Through this gap the entire Time Vortex can be seen, containing all that is, was, or will ever be. In the words of The Doctor, "Some would be inspired, some would run away, and some would go mad." It's initially suggested that this is what happened to the Master, though it's later revealed in The End of Timethat his madness was deliberately engineered by Lord President Rassilon to help pull the Time Lords out of the time locked Last Great Time War.
Dalek Caan in "The Stolen Earth"/"Journey's End" is arguably a case of someone who went sane from the revelation: despite exhibiting all the obvious characteristics of a Mad Oracle, having seen the whole of time itself left him utterly and completely disgusted at his own genocidal race and thus set things in motion to have the Doctor and Donna Noble defeat the Daleks.
In the episode "The Age of Steel", the Cybermen are defeated by the Doctor stopping their emotional inhibitors from working. This causes them to remember who they really are, and what they have become, and they subsequently go insane as the shock kills them. The Doctor effectively uses the same technique to defeat Mercy Hartigan in "The Next Doctor", severing her link with the Cyber King and allowing her to see the monster she's become, destroying her mind.
Ghost Light introduced Redvers Fenn-Cooper, an explorer and hunter who was unlucky enough to witness Light'ssleeping form in the cellar of a Victorian mansion. The experience turned his hair white and drove him into the depths of insanity. By the time the Doctor arrives, he's disassociated his own identity so well that if he does acknowledge his own name, it's in the third person.
The Torchwood episode "Adrift" has a victim of the Rift who's permanently insane as a result of looking into the heart of a dark star. He's living in a secret Torchwood-sponsored care home in an old bunker, with at least a dozen other patients. He screams for twenty hours a day...
In Upright Citizens Brigade, a house has a "bucket of truth" in it that shows immutable truth; most people are driven to absolute despair by the sights within. A police captain who has been wallowing in despair looks into the bucket and shouts at the heavens, "Don't you think I know that?!"
Buffyverse:Lilah's timid about entering the White Room, mostly because of one employee who went in there and ended up in an asylum as a result.
Married... with Childrenputs a humorous spin on this trope. In "Wabbit Season", poor Al Bundy has temporarily gone insane after an unpleasant incident at work, and when Peg brings him home, he's babbling about "selling a lot of shoes after midnight." A kiss from Peg brings him back to his senses, but what makes it even funnier is when Al explains what happened:
Al: Oh Peg, it was horrible. Sixteen straight hours of shoe-selling mayhem. The last thing I remember, I was on one knee, waiting on an overflowing glacier of a woman. The first thing they teach you when you're a rookie shoe salesman is, when you've got a fat one in the chair, never look up. I looked up, Peg! I saw underwear! It said "Saturday" on it! Beat Peg: So what? Al:TODAY'S WEDNESDAY!
In season 6, in the episode "If I Could See Me Now" we discover that Al has bad eyesight and experiences the world mostly as fuzzy blobs. The kids convince him to get glasses after driving home with Al behind the wheel. Upon finally getting his glasses Al sees the world around him, especially his house and family, as it really is. He clutches his head and screams in agony, parodying this trope. He finally destroys his glasses as he would rather cling to the world he knew rather than face the truth.
The 1980s revival episode "Need to Know" featured William Petersen investigating an insanity epidemic in a small town. It turns out a resident has discovered the meaning of life, but to hear the secret is to go crazy.
The Thriller episode "The Cheaters" follows a pair of magic spectacles from owner to owner. Each goes mad, as the cheaters show their wearer the truth of everything seen through them. The final owner decides to look at himself in a mirror, just as the creator of the glasses did before his death. They offer to let him off without seeing the truth, but he insists, and instantly goes mad and then kills himself.
This happens in Being Human, when Annie (a ghost) whispers to her killer, Owen a "secret that only the dead know." He snaps almost immediately. Interestingly enough, when George asks what she said, Mitchell shakes his head slightly, indicating that Annie shouldn't say—as well as the fact that he knows it too.
Lampshaded in Babylon 5, when G'Kar has a guest over for dinner:
Na'kal: "Breen. You've managed to import breen from homeworld. How?" G'Kar: "It .. isn't actually breen." Na'kal: "But the smell, the taste..." G'Kar: "It's an Earth food. They are called Swedish meatballs. It's a strange thing, but every sentient race has its own version of these Swedish meatballs. I suspect it's one of those great universal mysteries which will either never get explained or which will drive you mad if you ever learned the truth."
One episode of Criminal Minds is about a man who goes off antipsychotic meds in an attempt to access lost childhood memories, only for them to turn out to be so traumatic that they cause him to go on a killing spree.
In the Seinfeld episode "The Serenity Now" Jerry has become emotionally mature (as opposed to his shallow self) by letting his emotions out. At one point he asks George to "let it all out". We cut back later to see George in a similar state of emotional maturity, but Jerry is horrified beyond words. Even though Jerry doesn't go insane, the revelation burned out his emotional maturity and returned him to the shallow sitcom character he was before.
In Mystery Science Theater 3000 Tom and Crow are given psychotropic drugs for Pearl to observe the effects. Tom's view, while creepy, is apparently normal to him. What makes Crow go mad? The Milky Way bar Mike was holding is now a Snickers!
Another Played for Laughs in The Legend Of Dick And Dom episode "Hairwolf"; a man is driven mad by the horrors of the Hairwolf eating his hair and dances around giving cryptic warnings like "Don't go to the castle, it's dangerous!", "Don't play the bassoon in the bath, it's wrong!" and "Don't feed a whote rabbit brussels sprouts, it'll turn green!"
In season seven of Supernatural, Sam is being driven mad by memories of his time tortured by Lucifer in the Cage.
This is reported to be common when an ordinary human sees a Wesen in Game Face on Grimm. Apparently, a tolerance can be built up, as Hank demonstrates.
Leoben Conoy - "To know the face of God is to know madness."
The Hybrids, who control the Cylon Basestars, continually spout out apparent gibberish that some believe to actually be the words of "The One, True God."
D'Anna Biers experienced this trope first-hand in the Temple of Five after looking upon the faces of the Final Five.
The Stone Tape. The scientists question a man who used to play in the castle as a boy. He breaks down and reveals how a friend was accidentally trapped in the haunted room during a game of dare.
"He made out it spoke to him...and then the Others came."
"Can I meet him?"
"What for? He don't remember. They took him up the County, you know. They put him right. They can do that. He don't care a button he just la-a-a-ughs all the time!"
Sex with Brother Justin after he's transitioned into full-on Anti Christ mode has this effect in Carnivŕle.
At the end of Episode 11 of Season 4 of Breaking Bad, Walter is in desperate need of money. When he finds out his wife has had to give a huge portion of it away in a bid to keep their actions hidden, he lets out a scream of anguish ... and then starts cackling like a maniac.
According to The Talmud, there were four famous rabbis who were exposed to the mysteries of Creation: Ben-‘Azai, Ben-Zoma, Elisha‘ ben-Abuya, and ‘Akiva ben-Yosef. The first died, the second went mad, the third became an apostate (due to misunderstanding what he saw), and only the fourth one remained faithful.
In Gustav Schwab's ballad "Der Reiter und der Bodensee", a traveler lost in the snow unknowingly rides right across Lake Constance — the ice wouldn't normally be strong enough but it happens to be an exceptionally cold winter. When he arrives at a village and asks where he is, he realizes what he's done, imagines the cold abyss that was under his horse's feet, and dies of terror.
In The Goon Show episode "Lurgi Strikes Britain" Neddie Seagoon goes bonkers after realising how Grytpype and Moriarty have duped him, and starts yelling gibberish - the main symptom of the fake eponymous disease.
The Ravenloft campaign setting had tons of things that could drive a character insane, or at least prompt a Madness Check. Like direct mind-to-mind contact with a fiend. More common are Horror Checks (which cause lasting mental trauma, but usually not insanity) and Fear Checks (which simply cause the victim to panic.)
The Lords of Madness supplement indicates that the safest thing to do with the spellbook of an aboleth or the power stone of a mind flayer is to bury it, because trying to actually use the damn thing would do horrible things to the contents of your skull.
The Arcanis world-setting, along with the Living Arcanis campaign, featured Larissa. She started as the goddess of Fate, Prophecy, and all that jazz but one day she looked too far into the future and, well, went mad from the revelation. Now she's the goddess of sensuality, lust, and ladies (and men) of the evening. Apparently she's convinced that the fate she saw will come to pass and that she needs to get in as much pleasure now before it all goes kablooey.
Module Q1 Queen of the Demonweb Pits. No mortal being can behold the true nature of Lolth's Web (an eye-torturing, blazing tangle of twisted, rope-like strands) and remain sane. If someone under the effect of a true seeing, true sight or detect illusion spell looks at the Web for more than 1 minute, they will go raving mad.
The Black Spiral Dancers from Werewolf: The Apocalypse get their name because every last one of them walked the Black Spiral, an equally metaphorical and literal path that brought them face-to-face with the Wyrm, a cosmic embodiment of suffering and hatred. The experience breaks the minds of all but the most strong-willed like a twig; most Black Spiral Dancers take their deed name after whatever pathetic growls or mewling noises come out of their mouth upon "revelation."
Similarly, the Weaver, originally a cosmic embodiment of order and purpose, was turned into an all-consuming force for stasis when it tried to define the Wyld (a cosmic embodiment of primal chaos) and got the biggest "DOES NOT COMPUTE" in history.
The Wyrm itself was originally a general elegant destroyerto keep pattern from overwhelming order and provide fresh unordered energy for the Wyld, before the Weaver tied it up. The central Wyrm went mad from the impossibility of essentially imprisoning a fireball with string, and what few pieces escaped went crazy from realizing what had happened to the world without them.
Mage: The Ascension. One could say that Awakening to the realization that all reality is controlled by the belief of people, that your beliefs can change it more than others, and that humanity has become an apathetic race unwilling to realize the wonderment of the world is simply the start of a long, torturous road to death or complete insanity. Mages who violate the rules of reality too much eventually find themselves to become gibbering madmen unable to accept any reality but their own convoluted, insane one, eventually being ejected from the fabric of the world itself. Some Mages become brainwashed into reinforcing the frozen reality as it is (i.e. science) forming a contradiction in themselves against their dynamic nature. Then there's the Nephandi, the depths of depravity who would sell humanity out to Demons just for power. Since, by being a mage, you change reality with your beliefs just by existing, you're constantly violating general reality, you're always a little off even if you can avoid those three disastrous paths above.
You are a normal guy who realizes that humanity is just the playthings of vampires, werewolves, fairies, zombies, etc, and always has been since the dawn of time. The voices in your head telling you this is the truth doesn't exactly help.
And then there are the two groups who hear the voices far more clearly than anyone else. One goes insane to stop the voices from destroying their minds outright. The other experiences all the rage and hatred behind the voices, and starts coming up with genocidal plans against the supernatural without concern for anyone who gets in the way.
Then there's Obsessive Search, which is from the set called Torment... and has the keyword ability Madnessnote Cards with Madness can be played as it's discarded from your hands for any reason. Since your hands represent the spell you have in your mind right now, it's a power born from Madness....
The Rise of Eldrazi set is understandably full of characters going batshit insane upon seeing the eponymous creatures.
This game can (appropriately enough) be basically considered the Trope Codifier at least as far as role-playing games are concerned. Practically everything even mildly disturbing to a character's worldview has a chance of nibbling away at his or her sanity score, and full exposure to the horrors of the Mythos can cause him or her to snap (temporarily or permanently) rather quickly; thus, part of the challenge of playing is puzzling out a solution to the problems and pitfalls posed by the scenario without learning too much in the bargain. One edition of the rulebook even joked about it: "The only game where the big prize for finishing an adventure is a moldy old book which, when read, causes your face to melt off."
Cthulhu Tech, on the other hand, plays with this. Reading arcane texts, for example, can slowly drive you over the brink, as you'd expect exposure to the Necronomicon would. So does exposure to god-like aliens or their avatars or anything else that every natural law is struggling against. Realizing that the Doahanoids you vaporized with a charge cannonweren't isn't good for your grip on reality, either. However, since the Japanese Media Tropes the game adds to the Mythos call for a certain level of idealism, society at large is entirely aware of these effects, and There Are Therapists to reduce or eliminate the dementia characters gain.
The Call of Cthulhu adventure "City Beneath the Sands" actually turns this trope against the Eldritch Abomination. If the heroes fail to prevent the bad guys from linking their sleeping god-alien's mind with the collective subconscious of human dreamers everywhere, it's the god that goes mad, overwhelmed by contact with millions of human psyches (which are just as disturbing to it as vice versa). Sleepers worldwide just mainline nightmares for a night.
Many people who encounter the daemons of Chaos, especially the daemons of Tzeentch and Nurgle. (It's the smell, really...)
Archaon, the Everchosen of Chaos, is rumored to have once been a templar of Sigmar who read a forbidden manuscript and went batshit after learning the truth about the Gods including his own Sigmar. He is now the Big Bad among the warriors of Chaos and set to bring about the end of the world.
The past three editions of the Eldar codex have all contained the following quote:
Inquisitor Czevak: Ask not the Eldar a question for they will give you three answers, all of which are true and terrifying to know.
And then, because Warhammer 40,000 takes everything Up to Eleven, we have Kairos Fateweaver. Kairos was a freaking daemon whose god, Tzeentch, threw him into the Well of Eternity, a pool of infinite knowledge. Kairos came back with full knowledge of the past, present, and future, as well as two heads which are both insane. At any time one of them lies and the other tells the truth. Let's be absolutely clear: the premier avatar of the Warhammer 40,000 universe's god of knowledge and fate went insane when it found out the truth about the universe, every other aspect of the god that's tried it did not survive, and the god himself is too scared to look. Crapsack universe doesn't begin to describe this place.
This happens to nearly all of Tzeentch's followers. Tzeentch grants his more loyal followers, like sorcerers, enhanced powers over the Warp and the ability to weave vast, Machiavellian schemes, but the new-found omniscience drives them to insanity.
The Madness Meters have many varieties of ways to show how a multitude of stressful experiences, among them anything dealing with the supernatural, can either harden you into a sociopath or drive you insane.
The Unnatural Madness Meter is meant to represent the psychological strain of seeing something that doesn't conform to your worldview, not the inability to comprehend or accept what you've seen. One of the themes in the game is that magic and the supernatural may be weird and freaky, even to those that are clued in, but it is also part of the world and is not beyond understanding. Even Reality Warpers aren't an offense to that natural order of things, but the ones that dictate and sometimes change the natural order as needed. The Muggles also aren't as helpless as with most Masquerades and are in fact the ultimate source of magical power due to a symbolic variant of Clap Your Hands If You Believe.
Victoriana demonologists have a spell that can expose the recipient to all the beauty of Entropy in two seconds. The recipient invariably goes mad (at least temporarily).
Nobilis has a variant in Dementia Animus. If you are a mortal who succumbs to this as a result of witnessing miracles, you don't go mad; you go sane in such a way that you can see Mythic Reality, in which everything has a spirit and there's a guy holding up the sky. Of course, to everyone else who cannot see the spirit of your toaster, you appear totally bonkers and will usually come to a bad end. Fortunately, at least in third edition, you can receive succor, and forget what you have seen, by meeting Surolam, the dog-headed god of ordinary things.
A Streetcar Named Desire: Stanley rapes Blanche in an attempt to invoke Rape Portrayed as Redemption, but Blanche, who's already a little nutty, has a total breakdown instead and falls into permanent insanity. It really is as heartbreaking and disturbing as it sounds.
Hamlet: The eponymous character is sent awry by being told that his uncle had killed his father, by the ghost of his father. Hamlet himself believes he is merely pretending to be mad but it is made clear to the audience that he is no longer playing with a full deck.
Not really. It's never made clear if Hamlet really is mad or just pretending to be for his own purposes. He becomes far more lucid when he's either alone or with only Horatio. In any case, people have been debating on the subject for several hundred years, and are still doing so today.
Horatio warns Hamlet that the ghost might do this to him, and the ghost himself warns that just "telling" Hamlet about purgatory could do it:
"Hor." What if it tempt you toward the flood, my lord... and there assume some other, horrible form which might deprive [you] of reason and draw you into madness?
"Ghost" I could a tale unfold whose lightest word would harrow up thy soul, freeze thy young blood, [etc., etc.]
In Call of Cthulhu: Dark Corners of the Earth Jack is subjected to a series of revelations driving him more and more insane, culminating in him committing suicide in a mental institute after discovering that his father was possessed by a Yithian when he was conceived, making him not quite human
Maximillian Roivas from Eternal Darkness. He's committed after learning that his mansion is actually built over a monster infested city and murdering his servants due to his belief that they're all infected with Body Horrors. Most of them actually are. Since the game is directly based on Lovecraft's work, insanity due to revelations is a fairly major theme.
Additionally, Alex's sanity meter is set to a lower point every time you finish a chapter. Most cases of lost Sanity are an inversion of the trope though, happening when you're discovered rather than from learning anything.
In Neopets, a Neopian called Eliv Thade was driven mad from a book of unsolvable riddles. He died, and now his ghost speaks only in anagrams. (You know, "Evil Death"?)
Sephiroth from Final Fantasy VII. After finding out that he was born as part of an experiment to produce people with the power of an ancient civilization that was destroyed. That just emotionally unhinges him, though. What really sends him around the bend is that the ancestors of modern humans survived by hiding and letting them get eradicated. It probably didn't help either when he somehow learned that the "ancient" that was used to clone him was actually the alien who wiped them out, or that his own father was the one who performed the experiments on him before he was even born.
The fates of his two closest friends in Crisis Core likely didn't help much either. After finding out about his genetic manipulation (and instability) one committed suicide by forcing Zack to slay him in combat. The other rebelled against the organization responsible for said genetic manipulation. Sephiroth was never told the entire truth - or anything at all, really - about the Jenova Project. By the time of the events in Nibelheim, Sephiroth's personality had already gotten a lot darker...
Unfortunately, this method does not work on Deathwing, formerly known as Neltharion, probably because he's been mad for 10,000 years thanks to the Old Gods, and a knock on the head won't cure that. Back then, he was already crazy enough to tear his body up so badly he needed armored plating bolted into his skin in order to survive.
The Twilight Prophet, aka Archbishop Benedictus, leader of the Church of the Holy Light, apparently snapped and joined the Twilight's Hammer after reading a prophecy of the Old Gods' victory.
Similarly to Benedictus, Cataclysm also gives us Fandral Staghelm. He was never exactly stable to begin with due to the death of his son and his cold war with Tyrande, but the revelation that Xavius has duped him into causing the bloodshed surrounding Teldrassil proved to be the final straw for his sanity, leading him to becoming The Dragon for Ragnaros.
Archbishop Benedictus: I looked into the eyes of the dragon... and despaired.
Used as a game mechanic when fighting Yogg-Saron (an obvious expy for Lovecraft's Yog-Sothoth) - if you look directly at him for too long at a time while fighting, your "sanity meter" ticks down. Once you are at zero, you have Gone Mad From The Revelation and attack your teammates until they or you are dead.
Albedo from Xenosaga. He was always a high-strung kid, but the cracks begin to show when he finds out that he is immortal, but his (formerly conjoined) twin brother, whom he depends on completely for emotional support is not.
On the other hand, it's entirely possible that his worldview would make a hell of a lot of sense if we could grasp what it's like to be immortal.
Another part is when he came into direct contact with U-DO. If Albedo didn't go nuts from the aforementioned, this sure as hell did.
U-DO period. What happens when a a curious extra-dimensional god-thing is picking your brain for why your species is unknowingly trying to destroy the universe over and over again, and accidentally shows you what the end of all reality looks like ? This trope.
In Neverwinter Nights, Aribeth has gone quite mad from the revelation that she never loved Fenthick, and on top of that that Tyr has abandoned her. You have the option of trying to bring her back (which proves the second 'truth' false), or pushing her further into despair if you feel like being a Jerkass.
In Neverwinter Nights 2: Storm of Zehir, you can find a mind flayer in the Underdark Black Market who read the mind of a seer who foresaw the murder of Mystra that heralded the transition to D&D 4E in the Forgotten Realms. The illithid's brain couldn't process it and he is now reduced to inane gibbering.
Wallachia in Melty Blood went insane when he learned that nothing could avert the doom of mankind, only make it worse. To try and get around that he made a deal with a Dead Apostle to became a conceptual being for more time to find a solution. His insanity only got worse from there, eventually becoming a horrible raging unkillable monster. Crosses over with Despair Event Horizon, and it's alluded to that insanity is the eventual fate of all alchemists who try to calculate a future too far ahead.
Interestingly enough, Dust of Osiris reached the same conclusion...but Wallachia thinks he's more justified in becoming a monster than she was because (in Wallachia's opinion) Wallachia actually tried to solve the human race's self-destructive tendencies first before concluding that it was impossible, and Dust of Osiris did not make the same effort.
In Anchorhead, an IF award winner which is one gigantic (but very good) Lovecraft pastiche, there are several opportunities to reveal and go mad, including: looking closely at William, reading too much of the Tome of Eldritch Lore. Plus the various people you'll meet who Went Mad from the Revelation before you even showed up.
Also neatly subverted by Edward, who opens the story by murdering his wife and children for no apparent reason. It seems like he's fallen prey to this trope, but as it turns out, he had a very sane (if desperate) reason.
Invoked in the venerable Chrono Trigger. The "Confuse" status effect causes the character to go Laughing Mad, so it's really not surprising that any monster related to the game's Big Bad, the planet parasite known as Lavos, can and will inflict this status with any of its attacks unless you've equipped items that prevent it.
Subverted in the third season of Sam & Max: Freelance Police. Sam must travel through a dark dimension in search of a puzzle solution. He doesn't come back all there, but he gets over it in about half-a-minute.
Also subverted when the pair meet face to face with actual Eldritch Abominations but don't really seem to react adversely. They're even on good terms with one.
In Assassins Creed II, Altaďr notes in the Codex that many would-be Assassins could not accept the Badass Creed - Nothing is true. Everything is permitted. - and were mentally broken for it.
The reason why Sibrand cracked. The Reveal about the afterlife by the Piece of Eden turned Sibrand scared-shitless of death. His fears became even worse when Altair was after him. Everything that wore white and hoddy clothes would be immediatly killed by him, even if they were obviously just scholars and not assassins.
It's up for debate which drove Subject 16 insane first - being kept in the Animus for unhealthy amounts of time, being forced to relive dozens of people's lives and not being able to keep their memories, or his own, straight, or discovering the truth behind almost every conspiracy out there.
Jump too high or go too far off course in SSX Tricky, and the music is replaced with an unhinged voice that whispers disquieting non-sequiturs ...
According to the making-of book for Black & White, the true forms of both Good and Evil Gods cause this in the mortal beings of Eden. The player sees a hand (which becomes either godly or demonic depending on your actions), but everyone else simply sees a glowing symbol or a huge Creature doing your bidding.
Meta-example: It's occasionally speculated that this is a likely side-effect of viewing the source code of Dwarf Fortress.
In Knights of the Old Republic II, this is implied to be a side-effect of being in the Sith Lord Darth Nihilus' presence for any significant period of time. The entire crew of The Ravager are mindless zombies who are incapable of any form of individual thought or anything outside of their duties on board the ship. When you encounter Colonel Tobin, the Smug Snake who shot down your freighter earlier in the game, on board Nihilus' ship he is a gibbering lunatic who looks like this◊ and he begs you to end it all for him.
In Mass Effect, it has been suggested that this is the reason Manuel (the researcher's assistant on Eden Prime) is so unstable. He used the Prothean Beacon accidentally (or intentionally) before either Shepard or Saren, thus getting hit with the full effect of the Prothean's warning about the Reapers, which, according to Liara, would have "destroyed a lesser mind" than Shepard's.
Readers of the eponymous Elder Scrolls whose knowledge doesn't go much further than what the Scrolls really are, usually have their minds irreparably damaged from simply looking at one. Even those who've had training to actually read and understand a Scroll have odd personalities.
A reader without comprehension is dazed or stunned by the twisting patterns. One who can comprehend but isn't mentally prepared is struck blind. Even those with training slowly lose their vision. Eventually all readers receive nothing from the scroll but a foretelling that if they read again, whatever they may learn, they will also go utterly blind. The monk either then resigns or prepares his mind to receive the mind-blasting knowledge of his final reading.
Attacks by demons in the Diablo series are said to be enough to "leave one's mind in ruins," as evidenced by the Demon Hunter's sister from Diablo III and every PC except the Barbarian from Diablo II, though the latter takes a while to drive them completely bugnuts.
Psycho Mantis from Metal Gear Solid, due to finding out his father hated him enough to possibly want to kill him, causing Mantis to destroy his village and, years later, going too deep into a mind of a serial killer, causing him to adopt said killer's personality.
The Lab Rats from Borderlands 2 have been experimented on by Hyperion, until their eyes mutated and they started seeing... something. Whatever it is, they can't stop seeing it, and it drives them all over the brink.
Dr. Andonuts in The Halloween Hack, upon coming to the conclusion that the Chosen Four are trapped in the past. They were sent to another timeline.
Albert Wesker of Resident Evil plays up a pretty cunning Big Bad for most of the series and pitting everyone against one another as needed but after he hears he was the only surviving Tykebomb of an experiment by Umbrella's founder, he loses all semblance of organized thought and becomes convinced that he's meant for godhood.
Annette Birkin from Resident Evil 2 was a scientist who worked under the Umbrella corporation alongside her husband, William Birkin. She spent tons of time on research until Umbrella betrayed them both by stealing their latest creation, the G-Virus. William's resistance against Umbrella's mooks resulted in him being shot fatally and as a last act of desperate measure, he injected the virus into himself, causing him to mutate into a monster. Annette snapped as a result, which caused her to view almost everyone as spies of Umbrella and she defends her husband, despite the fact that he became a mutant.
The retelling of the game through Resident Evil: The Darkside Chronicles retcons Annette to avoid the trope. While Annette is still distrusting of strangers, she doesn't view Claire as a threat, is gravely concerned for her daughter's well being, and she actually attempts to stop monster William herself, though she gets mortally wounded for her troubles.
Police Chief Brian Irons was not exactly a nice guy, but seeing his city getting destroyed by the zombie outbreak and seeing Umbrella ditch him after all the bribes he had taken from them caused him to go insane; Irons deliberately hindered help to the police force by ordering all keys and weapons caches to be moved around in a bizarre order, hunted down the remaining surviving cops, and killed and raped the mayor's daughter while planning to stuff her body like a taxidermy trophy. When Irons meets Claire, he appears to be calm at first, but it isn't until he sees her again in his torture dungeon that he shows his true colors to her and planned to kill her as well.
Shin Megami Tensei IV adds another layer of horror to this with the Black Samurai. She travels around the land, freely giving away books that eventually render all humans who read them mad, and the insanity eventually melts their minds, reducing them to demons. It wouldn't be so bad if it was only a Tome of Eldritch Lore. But, as it happens, it's just literature. The people of East Mikado have had their beliefs in social inequality so blasted into their minds, the revelation that things can be different is so alien and terrifying, they. Just. Can't. Handle. It.
For a much darker variant, the White are unspeakably ancient spirits that strove to find a way to end the Forever War between Order Versus Chaos to free Humanity of both God and Lucifer. They found out not even a successful removal of God was enough to stop it, and snapped. They instead created a machine capable of creating a black hole across multiple realities to crush everything back into Nothing, but they could not activate it. So, they started affecting events so a certain champion would be eventually broken enough to join in the plan.
Similarly, the Big Bad of the first Super Robot Wars Alpha game became a Fallen Hero when he discovers the source of his investigation on a disturbance in the universe, turns out to be the Bigger Bad of Alpha, whom his people worshipped like a god, he doesn't take it well.
Most of the characters in the visual novel Saya no Uta are absolutely nuts by the time any of the three endings are over. Ryouko Tanbou, Fuminori's doctor, particularly suffers. After witnessing the reality of Dr. Ougai's experiments more than a year before the story, she's a classic case of paranoia who through her own intelligence has kept her paranoia carefully hidden in every day interactions.
After asking an omniescent cueball about whether the horrorterrors are good or evil, Rosegoesgrimdark. The scariest part is that we never get to see the answer ourselves. Again, it's shown to be subverted when she arrives on Skaia - she's still herself, (probably) sane and responds positively to meeting John, but she is far more aggressive and can only speak in incomprehensible Black Speech. After she dies and is revived on Derse, she returns to normal.
The datasphere in 8-Bit Theater. Once Red Mage and Thief concluded that reading it would drive a normal man insane and an insane man normal, (or kill him,) they decided to try it on Black Mage. Once he was incapacitated, they called Fighter over...
Who is fine. He even understood that the 612-dimensional sphere contained information concerning "every possible way to build any possible device to destroy every possible thing in all creation."
While it did shut down his higher brain functions for some time, Black Mage snapped out of his condition pretty fast. For the record, Black Mage's face, currently hidden in the shadow of his hat, made Onion Kid go into a coma. He later said it felt like everything good was gone from the world...
Captain SNES: The entire series is about video game characters finding out their lives are simply video games, and their sorrows and such are for our amusement. They don't take it well. Except for Kefka, who, being a nihilist, feels he was vindicated
Jack Hyland in Gunnerkrigg Court. They had the bad fortune to get caught in Zimmy's nightmare world when she had a psychic freak-out, ending up alone and unheard by the any of the others also caught in it. Although they weren't there long, it did not affect their mental state very well.
Though being possessed by an etheric spider might have had more to do with it.
Checkerboard Nightmare had the minor character Shrodinger the Cat, who could see every possible reality simultaneously and was, naturally, driven insane by the information overload.
In Sinfest, to a minor degree, this is why God does not show his face and uses the hand puppets. His showing a image of his face to two people caused a bit of a fight. Now imagine if He showed His face to a few more people...
When Slick ate the Fruit of Knowledge and found out he was a cartoon character, he tried to kill himself by jumping off a cliff. That works out about as well as you'd think —except that the river was Lethe.
Nodwick has a storyline about That Which Man Was Not Meant To Know, which has fallen into the hands of She Who Must Be Obeyed in the Lands That Know No Name. As it turns out, only men are not meant to know it. To women it's simply hysterically funny.
The Tom and Jerrymovie review has him reiterating to the viewers the basics of a particular scene: "A cat and mouse are driving a ship trying to save the daughter of Indiana Jones while being chased by a purple people eater, a dog on a skateboard, a performing ship captain, his hand puppet Squawk, two Mexican wrestlers, and a doctor riding an ice cream cart. Ladies and gentlemen, WELCOME TO THE MIND FUCK." Cue footage of the chase scene interspersed with clips of the Nostalgia Critic going bananas while Flagpole Sitta plays in the background and a big red "MIND FUCK!" flashes on the screen.
In the Teenage Mutant Ninja Turtles movie reviews, he tried to stay positive on the first and second movies, but still gives out negative responses. He tried to hope that the third movie, which even The Angry Video Game Nerd declares to be awful (he considered the first and second decent), will turn out good... then "5 minutes later"... we see him cuddling around in the bathroom, bawling incoherently, followed with much more Freak Out and inventing the word horrifuckus, after the revelation that the movie was really really... bad.
In a scene similar to the Tom and Jerry incident, one of the last moments in the Jingle All the Way review has NC explaining that the movie simply doesn't care anymore after Arnold gets a jetpack and starts doing silly CGI stunts. He then says, "You know what they say... if you can't beat 'em... join them." Then comes the insanity, the flashing "WE DON'T CARE!", and "Playmate, Come Out and Play with Me" playing in the background.
Linkara, the Critic's comic-reading counterpart, has a couple moments like these, which he once referred to as "Combine Harvester" moments, after the music that plays in the background. The first was when he read fanmail to Doom's IV that said that Rob Liefeld was a genius. The second one was when he discovers that Amazons Attack was technically a tie-in to Countdown.
While hers are much milder than her Spear Counterpart's, she has had a few of her own; most recently in Freddy Got Fingered where she, her friend Nella and co-reviewer Oancitizen have a "going mad montage" involving screaming, sausage and mayonnaise.
In the Lost Episode of Dune, when a navigator does its thing and she cries about just wanting to understand this ridiculously confusing movie.
When Obscurus Lupa can't work out the deeper meaning of MC Kung Fu's lyrics in City Dragon, she employs Kyle to work it out for her. After watching the film, Kyle starts spouting lines from the film out of context, gradually descending into madness.
Kyle: I can't speak the English language anymore! God help me!
The Nerd himself gets one after hearing Zelda's Bond One-Liner in The Wand of Gamelon.
In another James Rolfe-related video series called Shit Pickle, the monkey father from Munky Cheez 2 (yet another video series) goes mad after his kids keep saying "monkey cheese" over and over while watching the original, and those two words are all that the monkey dad can say from then on. Watch it here.
During part 2 of Christmas 2013 episode, he finds a good Spiderman game. Then checks who made the game. It's LJN, which makes Nerd go crazy.
Filthy Frank: A gem from the aptly named Lemon Guy: "Uh... I'm A LEMON!"
Once of the consequences of reading a good book discussed here. If knowing the unknowable is crazy I don't want to be sane.
Visions of The Presence from Nine Inch Nails' "Year Zero" ARG can cause anything from euphoria to madness.
Happens from time to time in the Whateley Universe because it is so near Lovecraft Country. When a demon manifests a small part of itself in downtown Los Angeles, Phase is the only witness (for more than a second or so) who doesn't go insane, and he requires psychic intervention and psychiatric therapy to cope with it afterwards. The demon eats or kills the other witnesses.
The SCP Foundation secures any number of artifacts that could easily qualify, ranging from memetic cognitohazards that will infest your mind just from knowing about them, locations with psychic and/or dimensional instabilities that can induce madness, outright Eldritch Abominations able to Mind Rape you simply from exposure, to [DATA EXPUNGED]. And those are just a handful of categories of items the Foundation has allowed to be catalogued without absolute redaction of all knowledge on the subject.
Bravest Warriors has Beth's Horse, who was rendered almost completely catatonic after discovering the meaning of the universe.
Horse: Paralyzed Horse's Log, July 3rd 3085... Every day, I hear and I see eternity. I am frozen in awe of my knowledge of forever...
The DCAU has many villains that were driven to crime because of the horrible circumstances forced upon them (Clayface, Parasite, etc.) but only one character seems to snap purely because of the knowledge he has received: The Question. When he cracks the Project Cadmus secret files and learns of the overthrow of the government of a parallel world and the ever-increasing likelihood that our Superman will likewise kill the president and instigate a worldwide catastrophe he loses it, begins to mumble incoherently to himself, and eventually tries to kill Lex Luthor himself so that Superman will never have the chance.Things go downhill from there.
This is parodied in a The Simpsons Halloween Special based on Night Gallery, in which Bart promises that a story based on a particular painting was so terrifying that it would instantly drive people mad. "..but it was far too intense. So we just threw something together with vampires. Enjoy!"
Homer: They're dogs! And they're playing poker!AAAAAHHHH!!!
The episode "The Blunder Years" has a magician make Homer return to his twelve year old self, only to have him go into a screaming fit throughout the night and a good chunk of the next day. It turns out it was a repressed memory of Homer finding the corpse of Smithers' father at the bottom of a quarry.
This is basically what happens to the Frank Grimes character after spending a bit of time with Homer. Grimes snaps after seeing how a Fat Idiot like Homer can have a better job than him, get paid more, have a nice house, and have decent food while he had to endure the hardships of his parents abandoning him when he was young, making just enough money to get cheap food, and living in an apartment that is above a bowling alley and beneath another bowling alley. After he sees people praise Homer for something so mind numbingly simple, Grimes goes off the deep end before he accidentally kills himself via electrocution.
Batman: The Brave and the Bold — In "Deep Cover for Batman!", Batman's only ally in this reversed dimension, Red Hood, is being questioned and tortured. We learn that he was disfigured by being thrown into a vat of chemicals by this universe's version of Batman. Sure enough, we see him look in a mirror, get a glimpse of green hair and bleached skin — and hear a truly maniacal laugh start to rise. Averted when he grabs a chair and smashes the mirror, presumably at the last minute he could retain his sanity. What made this so effective? Really, it's the voice actor — that laugh is as scary as anything Jeff Bennett ever unleashed.
The titular Ren from The Ren & Stimpy Show often went completely insane in various episodes leading to much horror. Two notable examples of this came at the end of "Svën Höek" where Ren completely lost it upon finding out what a mess Stimpy and Sven made in his house and the episode "Stimpy's Fan Club" at the end of which he contemplated strangling Stimpy in his sleep.
In "Hermit Ren," he gets so sick of Stimpy he leaves to join a hermit guild. They provide him with a cave and a boulder to lock him in forever. Completely alone. It doesn't take long for him to lose his mind. He gets kicked out for creating imaginary friends.
His Recycled In SPACE counterpart goes insane in "Space Madness" when, confined to a spaceship on a long mission, he is deprived of all contact besides Cadet Stimpy. Interestingly Stimpy does absolutely nothing to instigate this as the only bit of mischief he causes in this episode occurs after Ren is long gone.
Ren goes more than a little nuts at the end of "Farm Hands" when he thinks he and Stimpy are the last survivors after a devastating tornado. However, it turns out the farm's cow (a gorilla) also survive (and took a dump on them).
Ren and Stimpy both slowly lose their sanity in "Big Flakes" while they're trapped in the cabin.
In the episode of The Powerpuff Girls which deals with Mojo Jojo's origin, he is shocked to discover that prior to gaining his intelligence, he caused Professor Utoninum to hit the container of Chemical X that poured into his 'Perfect Little Girl Formula' resulting in the birth of the Powerpuff Girls. He is so shocked that he continuously mumbles "It was me?"
Also to point out, since it was the blast the girls were born from that transformed Mojo and gave him his intellect, it can be pointed out that he also caused his own origin.
An episode of Jimmy Two-Shoes had Jimmy finding that the horrible episode was All Just a Dream...until he realizes he just fainted and the situation is, indeed, as bad as it was. This happens several times until he's reduced to a blabbering mess.
Averted in The Real Ghostbusters episode, "The Collect Call of Cathulhu."note Yes, the spelling is a mistake (which is even pointed out in a DVD Commentary), but it is nonetheless how it appeared on the title card The guys lay eyes on Cthulhu himself... and aren't driven to madness. Word of God reasoned that it's because the Ghostbusters encounter horrifying things on a regular basis.
The Animaniacs short "Wally Llama" has the eponymous llama, who claimed to know the answer to every question, go crazy when he realises he doesn't know why it's 8 hot dogs to a pack but 10 hot dog buns. Admittedly, the seven minutes of harassment by the Warners prior to this probably didn't help his psychological state.
Freakazoid!'s origin has Dexter Douglas beamed into cyberspace after typing in a very specific line of code and exposed to the entirety of the internet. One can only imagine what would happen if he were exposed to the internet of today.
In the Evil Con Carne episode "Gridlocked and Loaded", Hector wants to steal all the gold from a boat but gets caught in traffic. When he finally makes it to the dock, he finds that somebody beat him to it. That somebody turns out to be the dorky intern he kicked out of the car moments before. This causes him and Boskov to literally go blind with rage.
Hector: That guy. That guy. THAT GUY IHATE!!!
Officer: Are you...all right, sir?
Hector: Yes, thank you. I have merely gone blind with rage. Now if you'll excuse me, I'm going to jump off the pier.
In the Looney Tunes short "Cheese Chasers", the dog goes insane when he tries to process the facts that the mice want the cat to eat them because they are tired of cheese and the cat wants the dog to kill him because the mice' behavior put him off of eating mice forever. He screams "it just don't add up!" and chases after a dog catcher to turn himself into the pound.
Played for laughs in South Park. In "Tsst", a group of television nannies try to correct Cartman's bad behavior before realizing what he is and giving up. Supernanny is the last one to attempt it. Within three days she's confined to a psychiatric hospital where she spends most of her time eating her own excrement and sobbing uncontrollably while screaming "From Hell! It's from Hell!".
Gravity Falls has Fiddleford Hadron McGucket revealed to have gone under this after working with the journals and repeatedly erasing his memory of any unusual events that occur in the town.
It is generally forbidden to collect all of the Tales Of A Thousand And One Nights in one set, and not just because it would be difficult to do so. According to legend, reading them all in one sitting will make whoever does so go mad from the sheer majesty of it. This is because your brain would short out from lack of sleep. Seriously, a thousand and one tales with a narrative thread that connects them would be a LOT of reading for a single sitting.
Paul Cohen said that he suspected that this had happened to Kurt Gödel, that his discoveries in logic caused him to have paranoid delusions later in life.
Some studies show that extreme pessimists have the most realistic grasp of their abilities, place in the world, and the probability of something happening. They're also most likely to be seriously clinically depressed. The study differs depending on which study is consulted and what questions you ask. If it's something that people, in general, are overly optimistic about (e.g. Wide-Eyed Idealist) the pessimists will be accurate. If it's something that people are overly paranoid about, (risk of death in a terror attack) the pessimists will be inaccurate.
The sad story of George Price, who used several mathematical and biological models to derive a mathematical equation that predicted that altruistic behavior and kindness do not actually come from true selflessness and concern for others, but are only naturally selected in order to promote one's own genetic heritage (people are more likely to be altruistic towards individuals with more similar genetic makeup, which explains why people often care more about their family than others). This theory predicts that there is no inherent selflessness in humans, and the altruistic acts are actually evolutionarily self-serving. Unable to accept such discovery, Price decided to randomly perform altruistic acts, which led him to give away most his possessions. When he was broke and kicked out of his rented house, he decided to take his own life. People said it was because of his despondency over his inability to continue helping the homeless.
Some have tried to poetically paint Friedrich Nietzsche this way. It sounds good: "He got so close to the Truth, a Truth he didn't believe in!" or something like that. He would have probably disagreed very much, being quite the despiser of any clichéd thought, but who knows? He really did pump out quite a few writings in the 1880s, and yet was very definitely insane by the end of that decade. Ultimately he succumbed to the brain disease that ailed him (identified as syphilis at the time, but whatever it was, it was there).
Hallucinogenic or disassociative drugs have the potential to cause feelings of this; with some individuals, permanent psychosis can result.
While not exactly "mad", Scientologists contend that anyone who reads the Xenu story without proper preparation (i.e., $200,000 in "donations") will become physically and mentally weakened. This may have something to do with a kind of "shock treatment" backfire similar to the VR in 20th Century Boys. However, there were originally plans to make a Film of the Book in order to let the public in on the joke secret. Hubbard changed his mind when he realized how much money he was making off the "audits".
A more mundane example happens whenever people suffer extensive bodily trauma. During that time, the body releases adrenaline that dulls the pain so your unaware of the extent of your injuries until after you escaped a dangerous situation. In addition, there is also the psychological shock where your mind is essentially refusing the reality of the situation by disconnecting from your emotions and whatever else is going on around you. This was best exemplified in Saving Private Ryan, where during the Normandy Invasion a soldier casually wanders around the battlefield looking for his severed arm after having it blown off.