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[[quoteright:317:[[Webcomic/GunnerkriggCourt http://static.tvtropes.org/pmwiki/pub/images/Jack_slipping_4748.jpg]]]]
[[caption-width-right:317:Get some sleep, Jack.]]

->''"Madness, as you know, is like gravity. All it takes is a little '''push'''!"''
-->-- '''SelfDemonstrating/TheJoker''', ''Film/TheDarkKnight''

A character has been a bit ... off for a while now. Maybe they just [[NotHimself haven't been themselves]], maybe they've gone as far as painting a RoomFullOfCrazy while reciting a MadnessMantra, or maybe they've gone through a MadnessMakeover, but it's apparent from their actions that their rational mind is losing its grip and they are sliding inch by inch toward insanity.

The end result of this varies, depending on the tone of the series and who the character is. If the series is [[DarkerAndEdgier dark and edgy]], they may go on a [[MurderIsTheBestSolution murderous rampage.]] On the other hand, if it's [[LighterAndSofter light and soft]], it may just be PlayedForLaughs, becoming a source for their hilarious dialogue and wacky plans. A villain is likely to have a VillainousBreakdown resulting in KarmicDeath, while a hero will just have a HeroicBSOD and then get better.

Occasionally, a character will be seen [[ReluctantPsycho holding back their insanity and generally keeping it in check]], until that final straw breaks the camel's back and they finally snap, having a massive FreakOut.

And most rarely, the Sanity Slippage is the effect of the Villain {{Gaslighting}} a victim.

A SuperTrope to SanitySlippageSong.

Compare GoMadFromTheRevelation, FreakOut, VillainousBreakdown, RoomFullOfCrazy, MadnessMantra, LaughingMad, and WithGreatPowerComesGreatInsanity.

* SanitySlippage/AnimeAndManga
* SanitySlippage/{{Film}}
* SanitySlippage/{{Literature}}
* SanitySlippage/LiveActionTV
* SanitySlippage/VideoGames
* SanitySlippage/WebOriginal
* SanitySlippage/WesternAnimation


[[folder:Comic Books]]
* ''Comicbook/TheKillingJoke'' is one take on the Sanity Slippage that eventually led to the origin of SelfDemonstrating/TheJoker. But the Joker admits he's an UnreliableNarrator and could be remembering wrong or making the whole thing up. He attempts something similar to crack [[spoiler:Commissioner Gordon. He doesn't succeed.]]
* Rorschach from ''Comicbook/{{Watchmen}}'' is clearly mentally unstable even before the event that causes him to [[JumpingOffTheSlipperySlope slide off of the slippery slope]].
* Jackson Georges from ''Comicbook/ExMachina'', Mayor Hundred's former NSA handler fits this trope. In flashbacks the reader is shown how the cryptic shard that Mitchell found when he got his powers slowly drives Jackson to levels of extreme paranoia. He develops an unfounded contempt for Mitchell, claiming that without Mitchell's appearance and the mystery of the shard, he could have foreseen and prevented 9/11. He becomes obsessed with protecting his family from dirty bombs and the like, buying a HazmatSuit and making tally marks on the wall to represent god knows what. It's clear he's a step away from the deep end. Darkly subverted when [[spoiler:in desperation to save their failing marriage, his wife breaks into his work shed and steals the shard. A few seconds near a TV are enough to drive her completely and utterly insane, leading her to kill her daughter, husband, and dog. She even chops off her own arm with the shard itself. It was an incredibly jarring and brutal twist on the slow burn of paranoia the reader had been witnessing for months.]]
* J. Jonah Jameson from ''ComicBook/SpiderMan'' suffered a nervous breakdown late in Marv Wolfman's run, to the point where he believed Spider-Man was stalking him. However, Wolfman left the book before long, and Roger Stern {{retcon}}ned the whole thing away as mind-control.
* [[Comicbook/{{Azrael}} Jean-Paul Valley's]] stint as Franchise/{{Batman}} during the "Knightquest" portion of the ''ComicBook/{{Knightfall}}'' storyline was this. After being doused with the Scarecrow's Fear Gas, the hypnotic trance known as The System kicked in, haunting Jean-Paul with images of his father and of Saint Dumas, the "creator" of the order he once was part of. As he's haunted by these apparitions, The System drives him to be more brutal and continuously modify the Bat-Costume, the pinnacle being when he allowed Abbatoir to die, condemning his captive to death, modifying the Bat-Costume to the point where it was less Batman and more Azrael and outright alienating Robin, Commissioner Gordon, and ''Bruce Wayne'' and deciding that all criminals need to be put out of their misery. It's at that point that Bruce decides enough is enough and sets out to take back the Mantle of the Bat.
* In SonicTheComic in the events leading up to the ''Sonic Adventure'' adaptation, Robotnik begins to lose it, first trying to [[EndOfTheWorldAsWeKnowIt destroy Mobius]], and later gathering the Chaos Emeralds, the Freedom Fighters, and Chaos itself to his retreat so they would all die together. After this fails, he becomes little more than a catatonic, drooling mess in ''SonicTheComicOnline.''
** In the same vein, Dr. Eggman in ''ComicBook/ArchieComicsSonicTheHedgehog'' goes into a slow burn SanitySlippage after Sonic, Tails, Knuckles and Amy are able to rescue the captured citizens of Knothole, set them up in the nanite-built city of New Mobotropolis, and defeat the machine that defeated Sonic earlier. Things get worse when Knuckles-as-Enerjak destroys Eggman's city and sky fleet and, by the time issue 200 rolls around, Sonic delivers one last defeat that causes Eggman to flip out, ''tear his mustache apart'' and devolve into a blabbering mess.
* After Optimus Prime dies ([[TheyKilledKenny the first time, that is]]) in ''ComicBook/TheTransformers'', Megatron takes it poorly, and becomes convinced Optimus is still alive and planning something. His madness eventually winds up causing him to shoot at the Space Bridge, which promptly explodes and apparently kills him. [[spoiler:Or not, as it turns out Megatron was just ObfuscatingInsanity, and using his 'death' as a cover to return to Cybertron. He just miscalculated when shooting the Space Bridge, resulting in a spot of LaserGuidedAmnesia.]]
** Happens to Shockwave in the UK comics, when he learns [[spoiler:he dies in the future]]. Determined to prevent this, he finds Megatron and sets him on Galvatron (well... [[OpeningACanOfClones it's complicated]]). Then the two start working together. Shockwave, who didn't expect this, just snaps, and kills anyone who approaches him.
* Though the [[VillainProtagonist titular character]] of ''JohnnyTheHomicidalManiac'' starts out [[AxCrazy by no means sane]], he somehow manages to get ''worse'' over the course of the story, as his telling of the story gets steadily [[ThroughTheEyesOfMadness less believable]], he gets [[TalkativeLoon talkier]], [[MoodSwinger less predictable]] and increasingly [[BungledSuicide suicidal]]. It helps that he's being targeted by TheCorruption ([[UnreliableNarrator maybe]]), lives in a LivingLabyrinth, and [[ExactlyWhatItSaysOnTheTin regularly murders people]].
** However, toward the end of the story, [[spoiler: Johnny ''does'' kill himself and [[LunaticLoophole comes back]] ([[MaybeMagicMaybeMundane maybe]]), after which he stops hearing [[CompellingVoice compelling voices]] and seems much saner. He does, however, still murder people]].
* Issue #5 of ''[[ComicBook/KickAss Hit-Girl]]'' [[spoiler:shows Mindy having {{Hallucinations}} of Big Daddy, who advises her to go out and slaughter Ralph Genovese and the rest of his men in the horrifying ways that she'd been planning.]]
* In ''[[ComicBook/{{Convergence}} Convergence: The Atom #1]]'', Pre-ComicBook/{{Flashpoint}} Ray Palmer has been hearing a voice in his head that may or may not be Ryan Choi's and has been acting considerably loopy ever since he was trapped in Gotham.

[[folder:Fan Works]]
* Jack O'Lantern, the ArchEnemy of FanFic/UltimateSpiderWoman, commits increasingly violent and destructive crimes as the series progresses. He goes from robbing banks to taking people hostage to going on killing sprees to orchestrating a bloody city-wide MobWar. Even in jail, we see him fantasizing about carving up human heads the way people do Halloween pumpkins. What's unusual is that Jack always had these sadistic urges-the Sanity Slippage comes from the escalating nature of his crimes.
* ''Webcomic/AxisPowersHetalia'': Austria/Roderich Edelstein in the ''Fanfic/NineteenEightyThreeDoomsdayStories'' is portrayed for the most part as undergoing through this. His obsession in finding out [[HopeSpot whether Hungary survived]] [[WorldWarIII Doomsday]] grows increasingly desperate (and irrepressible) over time to the point that others eventually start wondering if he's gone delusional from grief. [[spoiler:He doesn't.]] It's also mentioned to have happened as well with Romano (hijacked by TheMafia as his brother's successor) and Poland (having his personality shattered).
* Calvin goes a ''little'' crazy trying to watch a pug in ''Fanfic/CalvinAndHobbesTheSeries''.
* Jack in Part 1 of ''[[CaveStoryVersusIMMeen Cave Story VS I. M. Meen,]]'' and for good reason. After being trapped inside an insane pedophile's sick mockery of a yuri pairing fanfic between his girlfriend and his girlfriend's best friend, being forced to work a part-time shift at a restaurant called Diarrhea Bell, being forced to watch the two girls 2-Girls-1-Cup each other right in front of his eyes, and being tickle-tortured and thrown in jail, Jack lets loose with this underrated gem of a scene, cementing this story's status as one of the secretly best fanfictions of all time:
-> ''"I am Jack. Woe is me for I am wrongfully imprisoned. I am Jack! Sad and unhappy am I without friends. BOO HOO!! BOO HOO HOO HOO!!! (blows snot into handkerchief and smears it all over the floor)"''
-> ''"Emptiness wells up in my tortured soul. I'm going to...GOING TO...(vomits all over the floor)"''
-> ''"I am Sue; I also am indeed BLEAUGH! (dumps mixture of random condiments and gross stuff on the floor)"''
-> ''"I'm just Toroko but I'm gonna barf too, and the MUSTARD, MUSTARD BARF MUSTARD BARF!!! (dumps ketchup and mustard all over the floor)"''
-> ''"(soaks hands with the combined mixture) BEHOLD the GOOEY SLOP of our SORROW! (smears it all over his face) IT IS...SLOBBER...DAMMERÜNG! THE TWILIGHT OF THE CONDIMENTS!!! (removes hands from face and screams to the heavens, palms facing skyward) WEEP FOR THEM, WEEP FOR THEIR SORROW-HO-HOHO-HOHH!!!"''
-> ''[[CaptainObvious "Yes, Jack, my delicate psyche has come horribly unglued!"]]''
* In the vein of the [[WesternAnimation/MyLittlePonyFriendshipIsMagic Cutie Mark Failure Insanity Syndrome]] described above in the Western Animation section, ''{{Fanfic/The Audience}}'' by Reality Check states that Trixie herself is diving into one as her special talent isn't magic like most unicorns, but rather stage magic, illusions and theatrical personalities. The constant heckling, jeers and challenges towards her achievements that she was receiving were making her the JerkAss that she was portrayed as in canon.
* Fanfic/TotalDramaStranded: Briony gets a major one very quickly when [[{{Jerkass}} Calvin]] begins relentlessly bullying her.
* From the sister story, Fanfic/TotalDramaSwitcheroo, Missy gets an even bigger one.
* ''FanFic/QueenOfAllOni'': Her [[ColdBloodedTorture encounter]] with [[EvilSorcerer Lung]] leaves [[VillainProtagonist Jade]] with some severe PTSD, which only worsens as time goes on. It finally culminates with her confrontation with Tohru in the Vault of Endless Night, which convinces her the heroes are all out to kill or [[SealedEvilInACan seal]] her, at which point she [[VillainousBreakdown snaps completely]].
* The final story of ''Fanfic/CalvinAndHobbesTheSeries'' has two separate plotlines: one concerning the return of [[KnightOfCerebus Thunderstorm]] and another concerning Franchise/{{the Slender Man|Mythos}} showing up. When the stories intersect, Thunderstorm starts displaying signs of this.
* Nav starts showing signs of this in ''FanFic/DiariesOfAMadman'', as he becomes far more reckless and depraved over the course of the story.
* Spike goes through one throughout ''{{FanFic/Zenith}}'', which stems from his UndyingLoyalty to Twilight.
* ''FanFic/{{Memories}}'' has Serenity. When we first see her, she's like Pinkie Pie, a happy, cheerful, harmless, fun-loving, chaotic, CloudCuckoolander of a prankster with a soft spot for Discord. [[spoiler: Then she dies and comes back to life.]] Cut to the epilogue and [[https://www.fanfiction.net/s/7656204/1/From-Here-to-Eternity sequel]] and she's [[spoiler: giving out [[SlasherSmile Slasher Smiles]], [[EvilLaugh maniacal laughter]], telling Discord that she wants to [[WeCanRuleTogether overthrow his mother and rule in her place,]] and finally saying [[SlowlySlippingIntoEvil that together they'll kill Celestia.]]]]
* In ''FanFic/BeingDeadAintEasy'', Seto Kaiba slowly loses his mind as the story progresses for a variety of reasons, including guilt over Joey's death, obsessively trying to find a way to save Joey, lack of adequate food and sleep, [=KaibaCorp=] not doing well, worry for his own life and Mokuba's, and [[spoiler:synchronization with the dying Joey]].

* Songs about going insane are quite common, actually. Many examples at SanitySlippageSong.
* "Stan" by Music/{{Eminem}} shows the story of a fanboy with a seriously screwed-up life and a downward spiraling sanity. The video starts with Stan bleaching his hair just like Eminem's, then Stan starts writing letters to him every so often in his room all plastered with posters of Eminem, then he sends Eminem a ''really pissed off'' letter complaining about how he missed Stan and his brother at a gig. When his pregnant girlfriend scolds him for wasting his day on watching Eminem, that's the final straw on the back, and he ends up tearing all his posters, tying his girlfriend in his car's trunk, and driving off a bridge.
** Then Eminem sends back a letter, and starts by apologizing for how long it's taken him to finally respond. Trippin'. Best part: In his response letter, Eminem decides to cite a story he heard on the news about a guy who drove his car off a bridge with his pregnant girlfriend in the trunk, in the hopes that it'll get Stan to calm down a bit. Then Eminem realizes ''the news story was about Stan''. "Damn," indeed.
* The Music/NineInchNails album ''The Downward Spiral'' is a ConceptAlbum that's about ExactlyWhatItSaysOnTheTin: the gradual destruction of an unnamed man, from the beginning, to [[spoiler:his suicide]].
* The Violent Femmes' "Country Death Song" is pure American Gothic: rural guy goes mad from isolation and boredom, [[spoiler: throws his little daughter down a well]], then broods over his guilt till...you can probably imagine.
* Music/PinkFloyd's ''Music/TheWall'' chronicles a man slowly alienating himself from the world, causing his mind to collapse on itself until finally what's left of his sanity stages an intervention and forces him to actually ''deal'' with his problems.
** The band's previous albums, ''Music/TheDarkSideOfTheMoon'' and (especially) ''Wish You Were Here'', were inspired by the real-life sanity slippage of former bandleader Music/SydBarrett, who had become impossible to work with. "''Now there's a look in your eyes / like black holes in the sky''". His former bandmates reluctantly dropped him and felt guilty about it ever after. The two albums were enormously successful, but the subsequent non-stop grind of touring to unappreciative audiences caused Music/RogerWaters to suffer a sanity slippage of his own, which directly inspired ''The Wall''. Which was an even more enormous success!
* By Music/CoheedAndCambria's third album, the author in the frame story of their sci-fi epic has started talking to a bicycle and making both death threats and declarations of love to the ex-lover for whom he wrote the story. In the previous albums the author was not a significant character, and the only real sign of his instability was the fact he was writing the kind of material you can make a Prog Rock ConceptAlbum out of.
* ''Music/{{Gorillaz}}'': Both Murdoc and [[TheWoobie 2D]] show signs of this as of phase 3, rambling and gibbering like never before. 2D seems a bit sharper than earlier chapters, though, while Murdoc's just gotten bolder and more malevolent.
* Napoleon XIV's immortal ''They're Coming To Take Me Away, Ha-Haaa!!" starts off sounding like a love gone wrong, but it turns out he's addressing his dog.

[[folder:Professional Wrestling]]
* Wrestling/{{Edge}} began to gradually lose his mind as he kept getting closer to a Hell in a Cell match with Wrestling/TheUndertaker. It took Wrestling/MickFoley to tell Edge that he needed to let loose to have a hope of winning, culminating in a two-word WorldOfCardboardSpeech: "I understand."
* Wrestling/RandySavage became increasingly paranoid of other wrestlers trying to make moves on Wrestling/MissElizabeth as time went on, which in truth, [[ProperlyParanoid they were]]. But as it is said, just because they're out to get you doesn't mean you aren't paranoid.
* Wrestling/BrianPillman, due to an increasing string of injuries cutting down on his in-ring time.
* This is how Wrestling/{{ECW}} explained the transformation of narcissistic Johnny Polo to the chronically depressed, manipulative cult figure Wrestling/{{Raven}}.
* Having his mask stapled to his head and then being hung by Wrestling/RingOfHonor's Hang Men 3 really took a toll on [[Wrestling/HunterJohnston Delirious's sanity]]. As the name implies, he was already a CloudCuckooLander but the experience drove him AxCrazy enough to concoct a poison designed to restrict the airway, which he stored in his mouth!
* Wrestling/MickieJames's obsession regarding Wrestling/TrishStratus started about as innocently as an ''obsession'' could conceivably be (she used Trish's moves in new ways, hung around, sung her praises, ect). But then Mickie started giving up her own good fortunes for Trish, first admirably but later...to the detriment of her own health. Then Mickie started dressing like Trish. Then she got ''jealous'' of anyone who spent any significant time Trish, be it Trish's preexisting protege Ashley or Trish's boyfriend Chad. When Mickie basically [[NotWhatItLooksLike rested her head on Trish's crotch]] and [[NoSenseOfPersonalSpace refused to move it]] that was enough for Trish but the descent of Mickie's sanity had only just begun.
* [[Wrestling/RonKillings R-Truth]] turned heel after losing out on a WWE Championship opportunity. And after that, his mind.
* [[Wrestling/BryanDanielson Daniel Bryan]]. Yes! Yes! Yes! Yes! Yes! And after Wrestling/AJLee left him at the altar, it turned into: No! No! No! No! No!
* In 2010, poor Wrestling/ShawnMichaels started losing his mind after not being able to beat Wrestling/TheUndertaker at Wrestling/WrestleMania XXV. And after Wrestling/WrestleMania XXVI, his career. He regained his sanity at this point.
* Wrestling/AJLee's descent into insanity began when Bryan first dumped her after Wrestlemania -- needless to say, he would regret it. It's been over a year and AJ still hasn't regained her sanity yet.
* Su Yung had been slipping toward insanity since at least 2009 thanks to an inferiority complex regarding Tracy Taylor. A tour of Japan was supposed to help her get better but thanks to a few encounters with "[[IronicNickname Sweet]]" Saraya in SHINE she seems to have completely lost it in 2014...[[Film/JuOn completely.]]
* If Su Yung's the long case, Kimberly Maddox is the alarmingly short one, as in two shows in two months short, over the fact she couldn't get a win in the Shine promotion. However, Leva Bates theorized that Kimberly already had narcissistic personality disorder, so she likely didn't start very far up the slope.

* ''Radio/BleakExpectations'': A few days on a dessert [[note]]No, it's an island [[ExactlyWhatItSaysOnTheTin made out of dessert]][[/note]] island drive Pip Bin utterly mad, to the extent that he loses track of time, and considers eating himself, only relenting when he realises this is "probably a bit of an own goal". He quickly recovers when he finds someone to boss around.
** PlayedForDrama with Harry Biscuit's mother, who after her husband died started believing she was literally a biscuit (named Susan), and dunked herself to death. After that, the Biscuit fortune was taken by their rivals, the Flapjacks, and Harry was sent to [[BoardingSchoolOfHorrors St. Bastards]].
** Subverted with Pip Bin's own mother, who after the death of her husband starts sitting in linen closets and claiming to be a tablecloth married to a curtain, before moving on to bizarre interior decorating tips (replacing the walls with geese, putting scatter cushions on fire), and then believing she's the host of a cooking show. In Georgian England. Only it turns out [[spoiler:she was faking it, and the minute her husband returns she goes back to normal.]]


[[folder:Tabletop Games]]
* A daily occurrence in ''TabletopGame/{{Warhammer}}'' and ''TabletopGame/{{Warhammer 40000}}''; living in an endlessly terrible CrapsackWorld will do that. Witches/psykers are especially vulnerable to Slippage, thanks to the source of their powers being the home of TheLegionsOfHell.
* Also appears in WarhammerFantasyRoleplay, it has a mechanic for going insane and lists quite a nice amount of mental illnesses for which your character can suffer
** As befits its source material, GaidenGame ''TabletopGame/DarkHeresy'' has mechanics by which players can go insane.
* ''TabletopGame/CallOfCthulhu'' is famous for introducing the SAN attribute, which drops a little each time the players encounter a monster or cast a spell, or something.
* Everyone in ''TabletopGame/NewWorldOfDarkness'', from normal humans to blood-hungry vampires to reality-bending mages, has a KarmaMeter. As you slide down the slippery slope, you tend to become a little more unstable with each step, until finally, humans are reduced to raving lunatics, vampires and werewolves go nuts and become meat-hungry animals, mages and changelings fly off the deep end and lose the ability to separate reality from fantasy, and prometheans lose hope of ever becoming humans.
* The ''TabletopGame/OldWorldOfDarkness'' also has sanity-slipping {{Karma Meter}}s, though not all splats have them.
* The fan-made ''World of Darkness'' game ''TabletopGame/GeniusTheTransgression'' is unique in that players start out insane by nature of their [[MadScientist profession]], and as they lose Obligation start unconsciously [[RealityWarper altering reality]] to fit their delusions.
* ''TabletopGame/{{Exalted}}'' loves this trope:
** The Solars gradually experience this as they become more and more godlike, from both the Great Curse and general detachment from humanity and less powerful divine beings.
** Being close to a Primordial War survivor in the First Age can be dangerous, humiliating, and bad for your physical, mental, and social health.
** Also happens to Infernals. They have access to Yozi Charms. Everything the Yozis are, is made of Charms. Most of the Yozis are insane, and their Charmsets tend to be arranged so that the good stuff with no drawbacks is padlocked by something with benefits that makes you a little crazier. The best example of this is Kimbery, who has an entire Charm tree (built on ThePowerOfHate) locked behind something that permanently skews the sanity of its user to be either more naive or more vindictive, depending on the chosen variant.
* In ''TabletopGame/FadingSuns'', Psychics and Theurgists are prone to "Urge" and "Hubris" respectively.
* Characters in ''TabletopGame/EclipsePhase'' are very hard to [[DeathIsCheap kill permanently]] due to [[BrainUploading cortical stacks and backups]], fortunately for [[KillerDM GMs]] there's a mechanic called "stress points" that can cause psychological disorders or permanent catatonia if the PC lets them accumulate.
* Any KillerGameMaster worth the title can put this into ''any'' game.

* Blanche in ''Theatre/AStreetcarNamedDesire'' as well as the film adaption with VivienLeigh.
* ''Theatre/SweeneyToddTheDemonBarberOfFleetStreet'' does this with its eponymous character via [[SanitySlippageSong "Epiphany"]].
* The title characters in ''Creator/WilliamShakespeare'''s ''Theatre/{{Macbeth}}'' and ''Theatre/{{Hamlet}}'' gets an obsessive variety.
* The title character of ''ThePhantomOfTheOpera'', though your mileage may vary on how sane he was to begin with. But he's definitely completely off the beam by the end, determined to have Christine at all costs, even if he has to blackmail her into marriage by threatening to kill her lover.
* In Theatre/ShrekTheMusical, Fiona has a moment of this in "I Know It's Today" from waiting to be rescued [[GoMadFromTheIsolation from a small room in a tower for over twenty years]].

[[folder:Visual Novels]]
* Sakura in ''VisualNovel/FateStayNight''. It's like everything anyone ever says to her is another stab at her self confidence. And then Shinji tries [[spoiler:to rape her one more time, and then he'll tell Shirou about it]]. Yeahhhh things kind of go downhill from there. Oh, and she was already [[spoiler:eating people in her sleep]], passing out frequently and also quietly going crazy anyway. [[spoiler:She does get better, however]].
* ''VisualNovel/NineHoursNinePersonsNineDoors'' has [[spoiler: Clover, waking up and being forced into playing the Nonary Game. For a second time. She is fine over this. What gives her a dive in the deep end, is Snake's death. Apparent in the "[[MultipleEndings Axe]]" ending.]]
** [[spoiler: The [[WordOfGod author has suggested]] that something traumatic changed Akane in the previous Nonary Game, leaving her cold, vengeful and capable of eliminating everyone who gets in her way.]]
* ''VisualNovel/HigurashiNoNakuKoroNi'' has this occur several times, almost once an arc, and often bloodily.
* The [[Franchise/WhenTheyCry sister series]], ''VisualNovel/UminekoNoNakuKoroNi'', reveals in the fifth arc that [[spoiler:Natsuhi]] has slowly been losing it since [[spoiler:Kinzo died]] ''two years'' before the story begins.
** Arc 3 of ''Umineko'' also has [[spoiler:Eva/Eva-Beatrice]] ''really'' losing it, first after [[spoiler:finding the gold]] and then after [[spoiler:Hideyoshi is killed.]] By the end of the arc, she's gone completely [[AxCrazy apeshit]] and [[spoiler:shoots Battler]].

[[folder:Web Comics]]
* Jack from ''Webcomic/GunnerkriggCourt''. He started off as a pretty normal guy, then he briefly got pulled into a DarkWorld and saw some ''very'' unpleasant things. Since then he became increasingly antisocial, paranoid (at one point he starves himself because he's convinced the Court has laced his food with nanobots to track him) and amoral (compare his treatment of the Laser Cows to his treatment of the Guard Robot). [[http://static.tvtropes.org/pmwiki/pub/images/Jack_Progress_7447.jpg Heck, even his appearance became worse over time.]] Fortunately, now that [[spoiler:the whitelegs is out of his head,]] he's gotten almost back to normal. Oh, and [[spoiler:[[TheCuckoolanderWasRight he was right]] [[ProperlyParanoid about the food]].]]
* Vaarsuvius spent most of "Don't Split The Party" undergoing this in ''Webcomic/TheOrderOfTheStick''. [[spoiler: They ultimately recovered but not before committing an act which may have completely crossed the MoralEventHorizon.]]
* Jin of ''Webcomic/WapsiSquare'' suffers from a bad case of this after [[spoiler:destroying the calendar machine. It was actually built at least partially for the purpose of keeping her sane.]]
* ''Webcomic/{{Homestuck}}''--
** Karkat starts getting shades of this after a particularly brutal TraumaCongaLine. [[spoiler: Two of his friends were murdered in from of his eyes, two others are on killing sprees, he's dragging his newly-blinded friend's body (and accidentally drops him down some [[RunningGag stairs]], and he gets a message from his girlfriend, pronouncing the details of another murder - and when he tries to contact her, one of the AxCrazy trolls responds, hinting that she's been killed.]]
--> There. Good as new, best friend! It's like it never happened. No one can ever blame you for dropping him down the stairs now. Stairs? What stairs! Ha ha ha!
** Rose starts showing signs of it too, around the time [[spoiler: her mother died.]]
* ''Webcomic/GarfieldMinusGarfield'': With no cat to give him sarcastic remarks, Jon Arbuckle slowly descends into madness. Examples include [[http://garfieldminusgarfield.net/post/27473059 smushing ice cream cones into his face]], [[http://garfieldminusgarfield.net/post/40406640 dressing up for a date... that's in three weeks]], ''[[http://garfieldminusgarfield.net/post/78032638 jumping in the streets wearing a party hat]]'', [[http://garfieldminusgarfield.net/post/81381173 chasing cars in the manner of dogs]], [[http://garfieldminusgarfield.net/post/503880743/try-g-g-in-book-form breaking]] [[http://garfieldminusgarfield.net/post/26654167 down]] sobbing at the most random times, [[http://garfieldminusgarfield.net/post/30759171 Madness Speak]], and, finally, [[http://garfieldminusgarfield.net/post/69159474 being sent to a Mental Hospital]].
* ''Webcomic/BittersweetCandyBowl'' has Lucy having a mental breakdown when Michael falls off a rock bridge while saving her.
* In ''Webcomic/{{Pacificators}}'', one of the best Pacificators they had, [[DisproportionateRetribution Castella]] [[HeWhoFightsMonsters Brandsford]], snapped and [[NightmareFuel murdered thousands of people]] before she was killed by a suicidal guy. Ever since, the regular people have hated the people who has [[ElementalPowers powers]], because they [[TearJerker fear another Castella Brandsford]].
* Happens to Benjamin Prester in ''Webcomic/AMiracleOfScience'' when [[spoiler: he believes that his partner Caprice has been killed]]. He becomes increasingly violent, and he starts acting more like he did in flashbacks - [[spoiler: when he had full-fledged ScienceRelatedMemeticDisorder]]. The two biggest clues are [[spoiler: he redoes his hair in a particular style when in MadScientist mode, and he introduces himself as Benjamin when fully sane but as Ben when in the throes of SRMD.]]
* In ''Webcomic/DistortionNuzlocke'', Johnny goes through this more and more as the story goes on. He was already pretty messed up, but his fantasies cause him even more pain.