Trauma-Induced Amnesia

Sometimes, when somebody goes through a severe, emotionally traumatic experience or suffers a physical head injury, their brain removes the memory of that event; this causes Trauma Induced Amnesia. These memories can be often recovered over time through therapy, magic, or whatever is appropriate in the setting; but sometimes, another traumatic experience will bring them to the surface in Flash Back form. Sometimes depicted as appearing only in Bad Dreams, which often results in Dreaming the Truth. Sometimes, the memories simply come back on their own. And sometimes, re-experiencing the original trauma will bring them back like flicking a switch.

Related to Heroic BSOD. Subtrope of Laser-Guided Amnesia.

Anime and Manga

 * In Macross Frontier, Ranka fits this trope to a T: . Furthermore, when she next meets the Vajra, she starts to have traumatic Flash Backs to the aforementioned event.
 * Used in Macross Plus,
 * A particularly well-done example appears in Elfen Lied, in which Kohta has Trauma Induced Amnesia.
 * Suzaku Kururugi from Code Geass ; the trauma from the realization of what had happened caused him to develop amnesia about it. After, he gets the memories back and is so shaken that he goes into an Heroic BSOD.
 * In the spinoff game Lost Colors, the Featureless Protagonist.
 * Neon Genesis Evangelion: He might still remember it somewhere deep down, as evidenced by brief flashes of  while trapped inside his Eva after Zeruel. Though the viewpoint might suggest that he saw someone else's memories.
 * arc of Higurashi no Naku Koro ni. Actually, the manga version of Onikakushi-hen has this too. That is, until Keiichi notices his room...
 * Princess Tutu did this with not one, but two characters—Rue Her memories are all dug up by the end of the first season. Fakir takes a little longer to remember his traumatic past:
 * Casca from Berserk suffers this, along with being driven completely mad, after.
 * Vaiya experiences this during ''MD Geist II: Death Force.
 * Snow girl Yukime from Hell Teacher Nube loses her memories
 * Yuuichi from Kanon forgot nearly everything about the town where Nayuki lived in because . This drives the plot, by the way.
 * Naruto: Sasuke Uchiha forgot two things after the massacre of his family. One is that he . The second is that  . He doesn't remember either event until Itachi's.
 * A good portion of the clients in Nightmare Inspector have been through something traumatic, thus why they're having nightmares in the first place. Unfortunately, few of them actually remember the event until near the end of the chapter.
 * Usagi aka Sailor Moon does this in the Sailor Stars manga, after  She's so traumatised that she blocks the incident out of her mind. Boy, does it hurt when she remembers. (In the anime, she was spared of seeing this since  )
 * Mamoru himself was left with amnesia after he survived a car accident that killed his parents. His amnesia is portrayed (mostly) accurately in that he spent some time in a coma before finally waking up, and when he did he could barely remember how to speak let alone anything that happened previously. He's also never fully recovered memories of the event or his younger life.
 * In the Yellow arc of Pokémon Special, Red's Pika suffers this after witnessing his fellow Pokemon getting blasted away and his trainer receiving a direct kick to the stomach from a Hitmonlee.
 * Nina Fortner/ has forgotten most of the memories of her Trauma Conga Line childhood when she is introduced in Monster.
 * Chapter 10 of Magical Records Lyrical Nanoha Force revealed that Lily's amnesia was due to the trauma of her life as a lab experiment, which caused her memory to deteriorate as she tried to escape her grim reality by retreating into the Happy Place of her mind.
 * In Fullmetal Alchemist, this is the reason why Al can't remember
 * Happens to  in one of the Detective Conan Non-Serial Movies, Captured in her Eyes, after   The victim spends a good part of the movie in an Heroic BSOD, barely able to take care of herself and others, and the trope is lampshaded as her doctor says she might be afraid to recover her memories due to the events that made her go amnesiac.
 * Also happens to a boy named Touma Tachihara in the fifteenth movie (Quarter of Silence), and the key to solve the mystery relays on him getting his memories back.
 * Kai Hiwatari of Beyblade lost his memory after trying to use Black Dranzer when he was too young led to the destruction of the Abbey. It's not clear if this is due to emotional trauma, or physical trauma from debris.
 * In the manhwa Totally Captivated, Ewon completely forgets a rather important childhood event because of the beating that immediately preceded it, and the hypothermia that immediately followed it - unfortunately for him the violent Hair-Trigger Temper mafia boss who this was also an important event for does remember, and gets fairly pissed off that he doesn't. He eventually remembers after a period of Poor Communication Kills which finally leads to him again almost freezing to death.
 * Tokiko Tsumura of Busou Renkin acquired this at the age of ten after watching a homunculus eat every single person in her school (Quite possibly including her parents, as her family never gets mentioned in the manga) alive, leaving her the only survivor (She managed to hide until she was rescued by Captain Bravo).As a result of this, she blanked out her entire life before waking up in the Alchemic Army's hospital, and never regains those memories.
 * This is what happened to Ganta from Deadman Wonderland, where
 * Happens to Jeudi from Honoo no Alpen Rose, who suffers this after being the Sole Survivor of a plane crash. The main plot of the series is about her and her boyfriend Lundi trying to make her remember who she truly is.
 * Poor from Utawarerumono finally ended up with this after all the crap she went through and practically reverted back to infancy, not even remembering how to speak and only remembering Hakuro's name. Arguably it was probably the best that could have happened to her.

Comic Books

 * One hypothesis about Wolverine's lost childhood memories was that they were too painful to think about so his healing factor suppressed them.

Fan Works

 * Danny suffers a rather extreme case in the Danny Phantom fanfic Lost, wherein he doesn't only forget the event, he gets full-blown retrograde amnesia as a combo of head trauma, PTSD, and creating black holes in his brain. He is forced to relive the trauma through real-life psychological flashbacks.
 * Melanie ends with this in the Spice Girls/Backstreet Boys fic, In The Dark. Not only does she revert to a child-like behavior, Melanie refuses to speaks with anyone she wasn't comfortable but recovers overtime.
 * A dramatic retcon version in Equestria Chronicles occurs with Iron Hoof, during his time as Iron Claw.

Film

 * The Machinist
 * The Blind Side: Michael has this; Sean mentions halfway through the movie about how "Michael's gift is his ability to forget" his Dark and Troubled Past, and near the end, Michael explains how he would "close his eyes" when bad things happened.
 * The cult sci-fi movie K-Pax contains one of these as part of The Reveal.
 * The Bourne Series (like the novels) is based around this concept. In the movies Jason Bourne  He awakens with no memory of who he is or that he is an assassin.
 * The Long Kiss Goodnight is based on this trope: The main character lives a normal life as a small town schoolteacher and mother of a young girl. However, she don't have any memories prior to waking up on a beach seven years ago. After a car accident, she discovers that for some unknown reason she's very good with knifes. And step by step, her old life is starting to come back.
 * This is the inciting incident for the domestic drama Regarding Henry, starring Harrison Ford. In it, the title character survives a gunshot wound to the head, only for the resulting pinched artery to affect his memory. Cue the rest of the movie depicting him coming to terms with not remembering anything about his life before the shot.
 * Jeanne, the protagonist of Don't Look Back, is unable to remember anything about her life prior to a traumatic car crash when she was 8 years old.

Literature

 * In Lois McMaster Bujold's Mirror Dance, Miles Vorkosigan suffers from amnesia after.
 * This is more of a subversion, since the amnesia is the result of a medical procedure, rather than emotional stress or obvious brain trauma.
 * In the Cal Leandros series, Cal was kidnapped by the Auphe when he was fourteen and dragged through a portal to their home world/dimension/whatever. When he escaped, he had no memory of what went on during those two years.
 * In Animorphs, Rachel loses her memory after being mobbed in bald eagle morph by a group of rowdy crows and slamming into a tree.
 * In See Jane Run - a psychological thriller by Joy Fielding - the very first thing we read is how main heroine Jane Whittaker forgets who she is on her way shopping. And what the hell are those blood stains on her clothes and this large sum of money in her pocket?!
 * While we've never seen the cause, the Duck Man from Discworld may suffer from this. His occasional, vague musings about life before he became a beggar suggest that something quite nasty happened in his past.
 * Cole has this in the last episode of Tracker. An imbalance in his life force containment device was triggered by having captured only one of a set of alien twins, and Cole was basically given a nasty electric shock that wiped out his memory.
 * Induced deliberately in Caliban. Kresh figures out who attacked Doctor Leving when he realized that it wasn't a failed murder attempt that resulted in her being unable to remember much about the evening in which it happened, but a calculated assault to make her forget what she had been doing at the time of the attack.

Live-Action TV

 * The first season of 24 had this happen to Teri as blatantly obvious padding. After escaping the terrorists who held them hostage, Teri tells Kim to stay in the car while she figures out where they are. Car goes over the side of the embankment and explodes, Teri collapses, and wakes up with no memory of who she is.
 * Claire on Lost lost her memory of her kidnapping by Ethan and the Others, requiring hypnosis to recall some details.
 * The Eighth Doctor of Doctor Who suffered from this in his only onscreen appearance and spends a good fourth of the movie recovering from it slowly. Of course, returning from the dead  apparently does that to you, even if it's not unusual for the Doctor.
 * And he does it again in the spinoff novels, after he destroys Gallifrey (the first time, not the time that the Ninth Doctor spends his tenure angsting about). Oddly, he never really gets his memory back. Both fans and a character who has actually been making a concerted effort to prevent him from remembering lost their patience eventually.
 * It finally gets revealed that it's not trauma-induced at all; as he points out, he didn't get it when he was destroying entire universes. In fact, he suffers amnesia because.
 * Also, in "The Next Doctor,"  The Doctor refers to it as a fugue state.
 * Firefly's River Tam is implied to suffer a strong case of this from her time at the Academy.
 * Or, one of the reasons she's so screwed up is because she remembers exactly what they did to her far too vividly.
 * This happens at least twice in M*A*S*H with Hawkeye. In one episode, he incorrectly remembers a friend of his pulling him out of a lake to save him from drowning. Hawkeye had suppressed the memory that his friend had actually  before he saved him. In the final episode, Hawkeye had another problem with recalling his memories when
 * Played for comedy, in Dinosaurs Earl and Fran suffered so much from their experiences with their two oldest kids while they are two, that they had blocked out the entire year.
 * In the Korean Series Winter Sonata, Kang Joon Sang gets hit by a bus at age 18 and loses his memory, only to have it return 10 years later when he gets hit by a bus a second time.
 * In an episode of The Twilight Zone a woman
 * The eponymous character of Dexter blocked out the memory of, which was apparently so traumatic that it still turned him into a serial killer even though he didn't remember it until towards the end of season one of the series.
 * He and both developed into serial killers with a penchant for extremely tidy dismemberment.
 * In Sharpe's Peril, Henry Simmerson loses his memory after being strung up naked in the Indian sun. It actually makes him a nicer person, compared to the arrogant bastard he was before, to the point he's even seen playing pat-a-cake with a young Indian girl.
 * In the season 9 premiere of NCIS Tony is shot and cannot remember what happened. A psychologist talks his through the preceding events until he can remember who shot him.
 * Similar to the above example, in the mid-season finale of the second season of White Collar,
 * It's worse for him because he has perfect recall, so not being able to remember something would be pretty jarring.
 * In the season 4 premiere of Castle after being shot Beckett tells Castle that she does not remember anything about the shooting.
 * A key part of the crime drama Unforgettable. The female lead has absolute perfect memory, but there's one day she cannot remember: the day her sister was murdered. She's convinced that if she can recover her memories of finding Rachel's body, she'll discover a clue as to who killed her.
 * The Highlander episode "Through A Glass Darkly": An Immortal has a kind of mental meltdown in which he takes his student's head and the trauma triggers amnesia and a Fugue State.
 * Episode "Patient Number 7": An Immortal woke up in a mental hospital with no memory of who or what she is, or why the police and armed thugs are chasing her.
 * Season 4 of Tinsel has Fred Ade-Williams suffering from Missing Time because of this.
 * In the NBC series Awake, Detective Britten cannot remember what happened before the car accident that killed either his wife or son, depending on which reality he's in.
 * The Sherlock episode "The Hounds of Baskerville" has Henry Knight claiming he watched his father being savaged by a hound when he was a young boy. It turns out that
 * The Sherlock episode "The Hounds of Baskerville" has Henry Knight claiming he watched his father being savaged by a hound when he was a young boy. It turns out that

Video Games

 * Used by the player character Daniel in Amnesia: The Dark Descent, hence the name. He writes a note to himself prior to taking a drug which causes him to lose his memory, and as you play the game you begin to learn why he did it
 * In Final Fantasy VII, Cloud Strife suffers a perfectly understandable case of Trauma-Induced Amnesia, considering the incredible Trauma Conga Line he suffers before the game even starts -- he's already: (1) endured a lonely, alienated childhood; (2) been told he's too weak to become a SOLDIER; (3) watched his hero Sephiroth destroy his hometown and nearly murder both his childhood crush Tifa and his good friend Zack; (4) suffered over four years of sadistic experimentation by Complete Monster Hojo; and finally (5) is forced to helplessly watch Zack die in a gutwrenching heroic last stand to protect him.
 * Though in his case, it's less amnesia and more broken memory. He was in a weird state after being experimented on, and created new memories from listening to Zack tell Cloud his story. After Zack died, he was able to pull himself together, yet his memories were still screwed up.
 * In Tales of the Abyss, Luke has Trauma-Induced Amnesia from a kidnapping seven years ago that wiped out all of his memories of the event—as well as all memories of events prior to the kidnapping—while Guy has amnesia about . In Luke's case
 * The PC of Geneforge 5 has this, from what information the player is able to gather. Many significant NPC's from throughout the series claim to vaguely recognize you, and new characters describe your past behavior from senseless rage to Superpower Meltdown. Though speculation is rampant, the true identity is only answered by the Shrug of God. Maybe it's just a device to justify re-explaining everything previous players should know, but new players wouldn't, and explain why the PC wouldn't have any defined relationship to previously famous NPC's.
 * This happened to Shadow the Hedgehog following his apparent death in Sonic Adventure 2, when he fell after teleporting Space Colony A.R.K. back into a stable orbit. Understandable, as there was presumably head trauma involved.  His quest in the next two games was to regain his lost memories. Poor Shadow, since he had only overridden the fake memory intended to make him destroy the world a few minutes prior to his apparent death.
 * Xenosaga:
 * In Silent Hill 2,.
 * Oichi from Sengoku Basara. It's revealed that after her was murdered before her eyes by her brother, she went crazy and was enslaved by her dark powers, which made her forget it all. By the third game, she's basically a blank slate.
 * Ventus of Kingdom Hearts: Birth By Sleep..
 * Shirou of Fate/stay night, Heaven's Feel route:
 * Ace Attorney: This was the given reason why Ema's and Edgeworth's respective memories of SL-9 and DL-6 were incredibly foggy and incomplete. Of, course, in Edgeworth's case
 * Invoked in Golden Sun. The antagonists decide the memory of their crimes out of the witnesses.
 * It turns out that Umineko no Naku Koro ni's
 * In Trails in The Sky, Joshua seems to be suffering from this, though nobody can figure out why.
 * May be a factor in why the Player Characters of Knights of the Old Republic aren't going to say anything about their pasts.
 * In Heavenly Sword, Kai is repressing the memory of, until she is forced to remember. To elaborate, being forced to remember in this case consists of
 * Ashley Riot, protagonist of Vagrant Story, begins the game believing that he once had a wife and son who were murdered by thugs at a family picnic, but Manipulative Bastard Sydney proposes an alternate theory: Ashley murdered an innocent woman and her child during the course of his duties as a soldier, and through a combination of this trope and military brainwashing, convinced himself they were his family to help himself cope with the grief. The game's writers deliberately left it vague as to which version of his backstory is correct.
 * Some of the events of Assassin's Creed II have been suppressed in Ezio's memories, and only become available to Desmond in Brotherhood when he has achieved a greater level of sync. These memories include giving a Viking Funeral to his father and brothers after their execution, finding out his girlfriend Christina has left him for another man and delivering an If You Ever Do Anything to Hurt Her... speech to her new fiancé, getting snubbed after trying to reignite his love for Christina during the Venezia carnival, and Christina dying in his arms after being attacked during the bonfire of the vanities.
 * In The Elder Scrolls V: Skyrim, a priestess from a cult of cannibals claims that the Dovahkiin lost a sibling when they were a child, and took a bite out of the corpse out of curiosity, making the two of them Not So Different. If the Dovahkiin denies any knowledge of this event, she claims that most people block out the memories of their first incident of cannibalism out of revulsion. Whether or not she's telling the truth is left up to the player to decide.

Web Comics

 * Amity of Miamaska suffers from this after hitting her head on the ground from a fall.
 * Partially trauma-induced and partially because she was just too young, Fiona from YU+ME: dream initially does not remember how or why her mother died.

Web Original

 * Played for laughs in AH Dot Com the Series, which has luakel undergo a traumatic event and this erase the memory of itself, except when other crew members bring it up and he has a fit. Notably the same thing happened to his mirror universe counterpart, who is now permanently Ax Crazy.
 * A plot device in Sailor Nothing.

Western Animation

 * Naturally, The Simpsons:
 * In one episode, Homer is hypnotized, which triggers his memory of finding a dead body in the old swimming hole.
 * Helga Pataki of Hey Arnold!! suffers from this in the episode "Beaned" when she's struck by a baseball hit by old 'Dangerous Lumber' himself, Arnold. After waking up fully recovered the next morning, Helga continues faking her amnesia to guilt-trip Arnold into taking care of her, but begins to feel sorry for forcing him to pay attention to her. She fakes another head injury which 'cures' her amnesia and uses her usual crabby bluster to try and put some distance between them, but is pleasantly surprised that he still wants to make sure she's okay.

Real Life

 * Truth in Television, at least as far as physical trauma (especially to the head) is concerned. On the end of emotional or psychological trauma, there is vigorous debate to what extent it occurs, but dissociative disorders - particularly dissociative amnesia - are what this trope is based off of.
 * It falls under a category called 'Motivated Forgetting'. It is divided into two categories - repression and suppression. Repression is the Sigmund Freud style "it's too hurtful to remember so your subconscious buries it" stuff, and suppression is when you actively try to forget something. Repression has a little bit of evidence in that child abuse victims often can not recall the abuse later in life. Suppression can also occur to a certain degree, wherein people who concentrate on forgetting something are less likely to be able to recall it at a later time when asked to do so.
 * It may not really count as forgetting, but shocking events which take a very short time to happen sometimes simply don't register in the brain in the first place; this can happen to road accident victims or similar.
 * Dissociative amnesia, dissociative fugue disorder, and dissociative identity disorder are the most extreme cases. Of course debate rages on as to how many true or planted examples there have been, but theoretically the brain is malleable enough when young so that if you experience emotional trauma as a very small child, your mind can protect itself by "pushing away" the memories, believing it didn't happen or it happened to someone else. Personally I've met two people who seemed to have some amnesia from their early years, and I believe it was real. But even if you don't remember it, it's still there. The individuals I knew had problems with eating disorders and substance abuse, and it wasn't until seeking treating treatment for those issues that they started delving into their memories. The brain can protect itself from immediate damage by blocking out the harmful memories themselves, but the trauma will always find some other way to manifest itself until it's dealt with
 * When he was a boy, Stephen King saw a friend hit by a train; he claims to have no memory of the incident.
 * Some sources say that this trope is completely false, that traumatic events can't be forgotten. Ever.
 * The sources that tend to assert that emotionally and psychologically traumatic events can't be forgotten (Ever) tend to be technically correct, in the adrenaline and heightened stimulus response in the hippocampus and parahippocampus of the brain tend to embed traumatic events more strongly in an individual's memory. However, that said, this trope does occur regularly and this is why: although the event itself cannot be forgotten, the mind will deliberately sublimate and repress the traumatic memory in order to try to retain a degree of emotional and mental stability in the case where an even would be traumatic enough to instigate a dissociative fugue. Many victims of violence, particularly sexual violence as children, will not remember the events until either a trigger brings back the suppressed memory or the memory suppression eventually resolves itself as the mind starts to deal with and handle the trauma (usually when the individual is an adult and emotionally stable enough to deal with it) - the memory often starting to re-appear through dreams or nightmares. Usually in these cases, there will be a generalised dissociative state immediately following the traumatic event, and some changes in behaviour or personality may be noticed over the short term.
 * One question that is asked of people being assessed for PTSD is whether or not they're unable to remember a significant part of a traumatic event. For those who are, they'll be able to remember a great deal of what traumatized them in horrifying detail with the exception of a portion of what happened to them.