History Main / InfectiousInsanity

* ''Anime/DragonBallZBrolyTheLegendarySuperSaiyan'': Paragus was a relatively normal Saiyan with more empathy than most before his son was born. When his son was proven to be abnormally strong, King Vegeta tried to have them both murdered so they wouldn't challenge his Throne. Broly more or less went insane from the combination of his first memory of Goku crying, almost being executed, having to escape Frieza blowing up the planet, and from his own unbelievably strength and sense of superiority that came with it. After years of raising a son that would occasionally hurt or even try to kill him, Paragus started to lose it. As Broly was the only person he had left, he couldn't abandon him, but the danger he posed to Paragus and the universe backed Paragus into a corner. As he tried to put on the crown to control Broly, his son woke up dazed and confused and childishly called after his father. They got into a struggle and Paragus got the crown on, but Broly had worked himself into a frenzy and almost killed Paragus yet again before the crown took over. Paragus was relieved but saddened by having to do this to his son. Yet as time went on, he went mad with power now that he controlled his son similar to how the power drove Broly insane.
* When [[spoiler:Asura is released]] in ''Manga/SoulEater'', his madness infects people across Shibusen, most notably [[spoiler:Stein]].[[spoiler:It's later revealed ALL the Great Old Ones have this power on a global scale including Excalibur and Death.]]
* Hao from ''Manga/ShamanKing'' is insane but particularly good at striking people at their emotionally weakest, having built a seemingly random band of spiritually aware random passers-by with otherwise wildly varying ideals. They're all insane in that they all want to kill every non-shaman on Earth, but behave like perfectly normal people around other shamans.
* Since the "criminal coefficient" that makes you a criminal in ''Anime/PsychoPass'' is heavily affected by stress, latent criminals tend to increase the coefficient of victims and onlookers, especially since people have become so accustomed to uninterrupted peace. [[spoiler:When some people fake their displayed crime coefficient to go on a crime spree, the populace goes absolutely nuts in fighting them back.]]

* In ''ComicBook/JohnnyTheHomicidalManiac'' and ''ComicBook/IFeelSick'' Johnny and Devi go on a date. Later, we find out that the painting that's been talking to her is part of the supernatural insanity that Johnny has. [[/folder]]

* Beneda in ''Fanfic/TheDarkLordsOfNerima'' was originally a weak and cowardly youma who tried to use Ranma and his circle of associates as a means of getting back into the good graces of the Dark Kingdom. However, after BecomingTheMask and spending enough time around people who are barely slowed down by helpless odds, their thinking rubs off on her and leads her to attack an enemy that she'd previously been scared to death of.
* In the ''[[https://archiveofourown.org/works/6233746/chapters/30195594#workskin The Two-Faced Turnabout]]'', [[Characters/BatmanTheJoker the Joker]] is called as a witness to the night that an Arkham guard was killed, and [[Franchise/AceAttorney Athena Cykes]] uses Widget [[TheEmpath to read his emotions when examining his testimony]]. Phoenix warns Athena to be careful about reading Joker, and it seems the trope is in effect when Athena starts calling Joker "Mr. J" and acts friendly and even flirty with him. [[spoiler:It is later {{Subverted|Trope}}, as it turned out to be an act by Athena. As a psychology student, Athena had already read about Dr. Harleen Quinzel falling for the Joker and becoming Harley Quinn, so she recreated Harley's fall to madness to get Joker to loosen up]].

* "Entry Taken From A Medical Encyclopaedia" (also known as "Buscard's Murrain") by Creator/ChinaMieville. When a specific word is spoken with the correct pronunciation, the speaker is infected and will continue to speak the word out loud.
* The first story in ''Literature/TheMartianChronicles'' deals with a telepathic society in which insanity is highly contagious. As a result, when you think someone is crazy (because they're claiming to be from another planet, for instance) the automatic reaction is to shoot them immediately. And possibly then shoot yourself, just to be on the safe side.

** "[[Recap/CriminalMindsS7E19HeathridgeManor Heathridge Manor]]" features a woman who believed that the devil had claimed her fellow actresses as his wives, so she attacked them and then disfigured her own daughter so the devil wouldn't come for her. Her son and daughter internalized those delusions, leading them to team up and kill "the Devil's wives," aka random women the son painted while a delusion of his mother spoke to him. The last shot of the episode is the daughter taking the hand of what she believes to be the devil himself (in reality, there's no one there). Prentiss outright says the titular house "breeds delusions."

** In Recap/StarTrekStrangeNewWorldsS1E03GhostsOfIllyria the crew is exposed to an illness that makes them addicted to light and each crew member becomes gradually unhinged, [[spoiler: except Una, who is protected by her Illyrian physiology and becomes the one who saves the day but at the cost of revealing her true ethnicity.]]
** In Recap/StarTrekStrangeNewWorldsS2E06LostInTranslation when the crew is having trouble getting a nebula refinery online Pelia correctly suspects sabotage. Meanwhile Uhura is having memory and cognition problems thanks to hearing a BrownNote. The saboteur turns out to be a crew member named Lt. Ramon, who is having the same symptoms as Uhura. He goes insane and [[spoiler: spaces himself trying to destroy the refinery.]] Uhura fears she will suffer the same fate, but with the help of Kirk, she [[spoiler: realizes that aliens who live in the nebula and are being killed by the refinery are crying out for help]].
* A mild case in ''The Creator/GeorgeBurns and Creator/GracieAllen Show'': anybody who spends more than a couple of minutes talking to Gracie starts getting confused about what they're talking about.
* In the ''Series/TheTwilightZone1985'' episode "Need to Know", insanity is spread throughout a small town by the repeated utterance of the meaning of life.
* In the ''Series/{{Firefly}}'' episode "[[Recap/FireflyE03Bushwhacked Bushwhacked]]", it is shown that this can happen to survivors of Reaver attacks. The horror of the experience drives them into becoming Reavers, themselves.
* ''Series/{{Farscape}}'': In "[[Recap/FarscapeS04E10CoupByClam Coup by Clam]]", SpaceMadness is treated as an infectious disease and anyone suffering from it is killed. A doctor blackmails the crew of Moya by giving them similar symptoms, and promising the antidote if they pay up.

* Clan Malkavian from ''TabletopGame/VampireTheMasquerade'' are walking catalysts for this trope. Sure, spreading madness is their [[OurVampiresAreDifferent vampiric superpower]] - but not all of them are in control of it, or even aware of what their capabilities. Indeed, before the Great Prank was revealed in 1998, even the Elders of the Clan [[MemoryGambit had no idea that they possessed the Dementation Discipline]].
** In the TabletopGame/NewWorldOfDarkness, there's [[TabletopGame/MageTheAwakening Dark Angel]] [[EldritchAbomination Aphasia]].
** Later Malkavia was added to ''TabletopGame/VampireTheRequiem'' as truly contagious madness among vampires, working similar to old Malkavians.
* ''TabletopGame/{{Warhammer 40000}}''
** The Blood Angels have a lovely case of this known as the "Black Rage." It's literally the psychic imprint of their gene-father the Primarch Sanguinius fighting almost to death in defense of the Emperor's Palace during the Literature/HorusHeresy, and then ''actually'' dying fighting Horus himself. It tends to make those that share his gene-seed randomly start living out his last moments, which turns them into [[AxCrazy terrifying close-combat assailants]]. It's also almost incurable, taking all but literal divine intervention, and even then it's only happened twice in 10,000 years.
** The ancient C'tan curse that created the original Necron Flayed Ones[[note]]mentally-damaged Necrons that try to recreate having a flesh-and-blood body by wearing the skins of those they kill[[/note]] is contagious, and non-infected Necrons stay well clear of Flayed Ones when they appear and sometimes even kill them to keep the curse from spreading.
** Ork special character [[DeadlyDoctor Mad Dok Grotsnik]] is so bloodthirsty that any Orks around him get caught up in his madness, so not only is he and his unit Fearless, unlike other special characters he can't leave a squad he's joined until he's the last one in it.
* ''TabletopGame/WarhammerAgeOfSigmar'': Flesh Eater Courts are created as a result of this trope: an Abhorrent Ghoul King is a particular kind of devolved, debased vampire, more like a raving flesh-hungry beast, ''but'' they're also all hopelessly deluded into believing that they're actually regal and noble kings presiding over courts of heroic and resplendent knights. Thus, when they come across communities, particularly those who've already engaged in cannibalism out of desperation or starvation, their delusions spread, and whole groups of people get swept up into the Ghoul King's internal narrative as a SharedMassHallucination, and become his "court" seeing themselves as noble soldiers and heroic warriors, all while outwardly degrading into deformed, cannibalistic savages.
* In ''TabletopGame/DungeonsAndDragons'', the degenerate [[FishPeople Kuo-Toa]] suffer from this as a result of centuries of inbreeding and the cruel regime of their patron deity. A Kuo-Toa who suddenly snaps during a religious rite or the stress of everyday life can inspire homicidal outbursts in its neighbors, so a special caste called Monitors closely watches a settlement's population for any signs of madness and exiles those whose sanity begins to break. These crazed Kuo-Toa fend for themselves on the settlement's periphery and act as the first line of defense adventurers will encounter. In other cases, Kuo-Toa clerics, called Whips, will imprison insane Kuo-Toa in dungeons beneath the temples of Blibdoolpoolp, ready to unleash them upon any trespassers - and the maddened howls of these prisoners add a unique flavor to religious services.

** One of the plots of [[GovernmentConspiracy MAJESTIC-12's]] Project OUTLOOK is to create a "psychological virus", a way of causing a cascading spiral of riots and unrest through manipulation of the media.

* The entire reason the title BigBad of ''{{VideoGame/Slender}}'' exists. So long as one person knows he exists (or possibly even ''knows about him in fiction'') he will keep showing up. And his victims who go off the deep end go to great lengths to spread knowledge of his existence to the next unlucky soul. [[InvincibleVillain And people, inevitably, get dragged into it by accident, too.]] [[FromBadToWorse And with the games, there's the chance]] [[YourMindMakesItReal that he is bleeding over into this world.]] Just a possibility, of course, but still... ParanoiaFuel, much?
* ''Franchise/TheElderScrolls'' series' backstory has [[TheCaligula Emperor Pelagius the Mad]]. Infamous for his eccentricities, Pelagius was prone to severe [[MoodSwinger mood swings]] and outbursts of AxCrazy violence. He did not show signs of madness as a child, being perfectly personable. However, his madness crept in when he moved to Castle Solitude, which was still said to be infected by the madness of his aunt, the [[GodSaveUsFromTheQueen Wolf Queen Potema]].

* This is one of the creepiest aspects of ''Webcomic/{{Homestuck}}''[='=]s Trickster Mode. First starting off as a PsychoSerum affecting only person, it's shown to spread upon physical contact with the uninfected.
* On the [[https://www.project-apollo.net/mos/mos002.html second page]] of ''Webcomic/AMiracleOfScience'', the TropeNamer of ScienceRelatedMemeticDisorder, the antagonist is shown acquiring an infection of SRMD from reading a book, ''Crank Theories in Robotics''. [[GeniusLoci Mars]], which is a sort of gestalt consciousness formed from everyone on the planet using ElectronicTelepathy, is also ''very'' worried about what might happen if a Martian were to come down with it.
* ''Webcomic/StandStillStaySilent'': Infection by a Kade results in being its puppet for a time before eventually joining its MindHive. Before that point, eye contact between a Kade puppet and normal person result in the normal person becoming a puppet themselves.

* In the ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' episode "Party Of One," [[spoiler:Pinkie thinks her friends don't want to be her friends anymore]] and so surrounds herself with imaginary friends, using flour bags or turnip-buckets for the bodies. When Rainbow Dash comes over, Pinkie uses her voice to supply the voices for her imaginary friends, and hides behind her "pile of rocks" friend to call Rainbow Dash a chump. Rainbow Dash responds by asking "who are you calling a chump, chump?" ''to the pile of rocks,'' as if she were catching some of Pinkie's insanity.
* In ''WesternAnimation/AdventureTime'' With [[DistaffCounterpart Fionna And Cake]], Fionna tells Cake not to touch the Ice Queen's tiara because she "might catch her crazy", which sounds like she's talking about "power corrupting" and whatnot since the tiara (and crown, in the original's case) is the source of her magic power. [[spoiler: But then later the Ice King's origin is revealed and he turns out to have been a sober, buttoned-down archaeologist before he found the crown, which he put on one day while indulging in a silly moment with his girlfriend, and as a direct result of that one act slowly became the Ice King we're familiar with today. And ''Fionna and Cake'' is a ShowWithinAShow that ''Ice King'' wrote.]]
* In ''WesternAnimation/InvaderZim'' there were two unfinished episodes that would have shown a cross between this and a computer virus.
** In The Trial [[spoiler:the Control Brain connects to Zim's pak to erase it and it starts going insane, even declaring Zim the Most Incredible Irken Ever!]]
** In Ten Minutes To Doom [[spoiler:Zim's pak comes off. Dib takes it and it later attaches itself to his chest. He starts acting like Zim, saying that he's going to take over the Earth, calling people filthy humans, and even calling himself Zim.]]

[[caption-width-right:350:Being in the stressful hubbub of a psychiatric ward could make you feel even more crazy! ]]

Cf. GoAmongMadPeople, where this is invoked on purpose... and very often [[BecomingTheMask becomes this trope]], either because madness is really infectious or just because of the level of "care" in the particular BedlamHouse. Compare MindVirus.

** Downplayed but important in "The Fisher King." The unsub was already mentally ill to begin with, which is why he voluntarily entered a psychiatric facility. But talking with one of the other patients there (Reid's mother) solidified and furthered his delusions. Mrs. Reid accidentally managed to convince him that her son and his colleagues were analogues to King Arthur's knights and that his daughter Rebecca was a metaphor for happiness, which caused him to abduct Rebecca and set a deadly quest for the BAU team in the sincere belief that doing so would heal his wounds.
** "Heathridge Manor" features a woman who believed that the devil had claimed her fellow actresses as his wives, so she attacked them and then disfigured her own daughter so the devil wouldn't come for her. Her son and daughter internalized those delusions, leading them to team up and kill "the Devil's wives," aka random women the son painted while a delusion of his mother spoke to him. The last shot of the episode is the daughter taking the hand of what she believes to be the devil himself (in reality, there's no one there). Prentiss outright says the titular house "breeds delusions."

* In the ''Series/{{Firefly}}'' episode "Bushwhacked" it is shown that this can happen to survivors of Reaver attacks. The horror of the experience drives them into becoming Reavers, themselves.
* ''Series/{{Farscape}}''. In "Coup By Clam", SpaceMadness is treated as an infectious disease and anyone suffering from it is killed. A doctor blackmails the crew of Moya by giving them similar symptoms, and promising the antidote if they pay up.

* Since the "criminal coefficient" that makes you a criminal in ''Anime/PsychoPass'' is heavily affected by stress, latent criminals tend to increase the coefficient of victims and onlookers, especially since people have become so accustomed to uninterrupted peace. [[spoiler:When some people fake their displayed crime coefficient to go on a crime spree, the populous goes absolute nuts in fighting them back.]]

* In the ''[[https://archiveofourown.org/works/6233746/chapters/30195594#workskin The Two-Faced Turnabout]]'', [[Characters/BatmanTheJoker the Joker]] is called as a witness to the night that an Arkham guard was killed, and [[Franchise/AceAttorney Athena Cykes]] uses Widget [[TheEmpath to read his emotions when examining his testimony]]. Phoenix warns Athena to be careful about reading Athena, and it seems to be the case when Athena starts calling Joker "Mr. J" and acts friendly and even flirty with him. [[spoiler:It is later {{Subverted|Trope}}, as it turned out to be an act by Athena. As a psychology student, Athena had already read about Dr. Harleen Quinzel falling for the Joker and becoming Harley Quinn, so she recreated Harley's fall to madness to get Joker to loosen up]].

[[folder: Anime & Manga ]]

[[folder: Film--Live-Action ]]

[[folder: Literature ]]

[[folder: Live Action TV ]]

[[folder: Tabletop Games ]]

[[folder: Video Games ]]

[[folder: Webcomics ]]

* This is one of the creepiest aspects of ''Webcomic/{{Homestuck}}''[='=]s Trickster Mode.
* On the [[https://www.project-apollo.net/mos/mos002.html second page]] of ''Webcomic/AMiracleOfScience'', the TropeNamer of ScienceRelatedMemeticDisorder, the antagonist is shown acquiring an infection of SRMD from reading a book, ''Crank Theories in Robotics''. [[GeniusLoci Mars]], which is a sort of gestalt consciousness formed from everyone on the planet using TechnologicalTelepathy, is also ''very'' worried about what might happen if a Martian were to come down with it.

[[folder: Western Animation ]]

[[folder: Real Life ]]

* When [[spoiler:Asura is released]] in ''Manga/SoulEater'', his madness infects people across Shibusen, most notably [[spoiler:Stein]].

* On the [[https://www.project-apollo.net/mos/mos002.html second page]] of ''Webcomic/AMiracleOfScience'', the TropeNamer of ScienceRelatedMemeticDisorder, the antagonist is shown acquiring an infection of SRMD from reading a book, ''Crank Theories in Robotics''.

* ''Franchise/TheElderScrolls'' series' backstory has [[TheCaligula Emperor Pelagius the Mad]]. Infamous for his eccentricities, Pelagius was prone to severe [[MoodSwinger mood swings]] and outbursts of AxeCrazy violence. He did not show signs of madness as a child, being perfectly personable. However, his madness crept in when he moved to Castle Solitude, which was still said to be infected by the madness of his aunt, the [[GodSaveUsFromTheQueen Wolf Queen Potema]].

* ''TabletopGame/WarhammerAgeOfSigmar'': Flesh Eater Courts are created as a result of this trope: an Abhorrent Ghoul King is a paticular kind of devolved, debased vampire, more like a raving flesh-hungry beast, ''but'' they're also all hopelessly deluded into believing that they're actually regal and noble kings presiding over courts of heroic and resplendent knights. Thus, when they come across communities, paticularly those who've already engaged in cannibalism out of desperation or starvation, they're delusions spread, and whole groups of people get swept up into the Ghoul King's internal narrative as a SharedMassHallucination

** [[spoiler:Hastur. Unlike vanilla ''TabletopGame/CallOfCthulhu'', Hastur is not an Elder God or Old One, but an infectious and pervasive force of decay. Knowing about Hastur or its related mythos trappings allows such decay to happen on a person's psyche, and "infected" people will become a vector in spreading Hastur's influence. Even worse is that it can infect places too, which also become [[AlienGeometries "insane" in their own way]]. Both places and people can infect eachother and vice-versa, until they are affected enough and get pulled to the [[EldritchLocation city of Carcosa]].]]

* A mild case in ''The Creator/GeorgeBurns and Gracie Allen Show'': anybody who spends more than a couple of minutes talking to Gracie starts getting confused about what they're talking about.

Cf. GoAmongMadPeople, where this is invoked on purpose... and very often [[BecomingTheMask becomes this trope]], either because madness is really infectious or just because of the level of "care" in the particular BedlamHouse.

** In ''Discworld/{{Hogfather}}'', HEX contracted psychosis after talking to the Bursar, which was something of a backfire since talking to HEX was supposed to ''alleviate'' the Bursar's[[note]]although on one occasion they used HEX to run one of those hokey "therapist" chatbots and it actually managed to confuse him into lucidity, whereupon he accused it of making fun of him[[/note]]. Ridcully, in a flash of insight, convinces HEX that it's been given a very large dose of dried frog pills (the Bursar's normal treatment), which puts it back in working order.
** In ''Discworld/TheAmazingMauriceAndHisEducatedRodents'', this trope applies to ''fear and panic'' among the Clan of TalkingAnimal rats. Because rats rely so heavily on their sense of smell and have the 'flight-over-fight' instincts of prey animals, merely smelling the fear-pheromones of scared fellow-rats makes them terrified and unable to think rationally.

* On the [[https://www.project-apollo.net/mos/mos002.html second page]] of ''Webcomic/AMiracleOfScience'', the TropeNamer of ScienceRelatedMemeticDisorder, the antagonist is shown acquiring an infection of SRMD from reading a book.

** There's a good possibility that many cases of these were somewhat true, insomuch as poor medieval milling techniques could allow Ergot to infest local bread stores, leaving to [[MushroomSamba fits of unknowingly drug-fueled insanity]] among entire townships.