I’m the rare girl who went to medical school with a love of watching whodunits and ended up — 10 gruelling years later — a forensic psychiatrist. Forensic psychiatry is the most thrilling job imaginable, but forensic psychiatrists in mysteries and crime TV have some very different roles than we do in real life. We spend our workdays in jails and prisons and justice centers and forensic hospitals, asking people questions, which often include inquiries about what led up to the worst things they’ve done in their lives.

Crime fiction is often way off in its portrayals of mental illness too. Unless we are mental health professionals ourselves — or we know and love someone with a mental illness — much of our experience of mental illness is shaped by pop culture. And in pop culture, mental illness is used as a trope, to surprise us, to scare us, and to make us laugh. This is not conducive to understanding people’s struggles — or to people getting the help they need — before a tragedy ensues.

In the spirit of stopping the spread of misunderstanding and stigma, here are the top 10 myths about mental illness in crime fiction, corrected:

1. Myth: Amnesia often makes people forget their identity. Amnesia is really not as common as you would think from watching crime movies and reading mysteries. Though Matt Damon takes us on action-packed adventures in the “Bourne” movies, and watching Liam Neeson in “Unknown” makes our hearts race, amnesia is not in the job description for CIA agents or assassins. Furthermore, amnesia just doesn’t work like that. Amnesia can be psychiatric or neurological, but the post-traumatic amnesia seen in these films with losing one’s one identity doesn’t just happen without a huge host of other problems.

2. Myth: Multiple personality disorder is a common mental illness. Multiple personality disorder (MPD) is also uncommon — despite what “Fight Club” or “Primal Fear” might make us think. In fact, many psychiatrists doubt if MPD (which has been renamed dissociative identity disorder) actually exists, with some considering whether it was just a creation of pop culture itself. Even if it does exist, it has already been overrepresented as the “twist” in more tales than most of us have seen in our entire careers. In reality, mental illnesses are not plot twists, but serious and potentially impairing diagnoses that people need to seek treatment for.

3. Myth: If someone’s behavior changes a lot — over the course of an hour — they probably have bipolar disorder. Dr. Jekyll and Mr. Hyde did not have bipolar disorder — he likely had an addiction. Bipolar disorder is not just switching your behaviour over the course of a day or night. People with bipolar disorder experience “highs” and “lows,” but these last days to — much more commonly — weeks. Bipolar disorder is not a personality quirk to make a character unpredictable.

4. Myth: It’s easy to “get off” for a crime if you have any symptom of mental illness. Merely being silent is not a mental illness diagnosis, as portrayed in “The Silent Patient,” a page-turner slated to become a film. While there is a vanishingly rare mental condition called catatonia in which patients often don’t speak, they have a constellation of other symptoms too — such as losing the ability to move, staying in the same odd positions for extended times with muscular rigidity, lack of response to external stimulation, and grimacing. Furthermore, silence alone certainly would not lead to (spoiler alert!) an outcome of forensic hospitalization — even for a defendant as beautiful as the character in the novel.

5. Myth: Mental illness can be treated by locking people away in isolation. Data demonstrate that solitary confinement itself can lead to psychosis, paranoia, perceptual distortions, and anger. In “Jane Eyre,” Mr. Rochester was not a romantic guy, locking his first wife in the attic — whether or not she was mentally ill. Jane is making a big mistake falling for him even if he is a rich and lovable curmudgeon. This is not appropriate male lead behaviour, and absolutely not an effective or humane treatment for mental illness.

6. Myth: Mental illness means people are always violent and unpredictable. Rarely would mental illness make someone unpredictably violent. People with mental illness are actually statistically more likely to be victims than they are to be perpetrators, something an early scene in “Joker” got right.

7. Myth: Psychotic breaks come on suddenly, for no reason. Psychosis doesn’t just hit someone suddenly like in “Me, Myself & Irene.” In general, a person doesn’t just “crack” with psychosis. Rather, delusions (fixed false beliefs) and hallucinations (most commonly hearing voices when no one is there) begin gradually over time. However, psychotic symptoms can suddenly appear rarely in the postpartum, related to sudden lack of sleep and hormone changes or if someone was using illicit drugs.

8. Myth: Bipolar disorder is a personality disorder. Glenn Close’s character in “Fatal Attraction” is a brilliant portrayal of severe personality disorder. Personality disorders — such as antisocial and narcissistic and borderline personality disorders, among many others — involve rigid, unhealthy patterns of thinking and behaving. However, personality disorders (and bunny-boiling) are not the same as serious mental illness. Serious mental illness is generally defined as including schizophrenia, bipolar disorder, and recurrent major depression. It’s important to understand the differences between these diagnoses, which are often not made clear in popular films.

Notably, antisocial personality disorder is the most common type of personality disorder in the criminal justice system. This is more anti- “the social order” as opposed to the way people often use “anti-social” to explain that they don’t feel like going out. Psychopaths are a subset of people with antisocial personality disorder. The most famous fictional forensic psychiatrist, Hannibal Lecter of “Silence of the Lambs,” and its progeny, fits best into this world of psychopathy. Psychopaths really are the mystery. They live and walk among us; they could be our neighbours, our co-workers, and (we think) our friends. When Hervey Cleckley, MD, first described psychopaths in the 1940s, he wrote that they wore the “mask of sanity” because they were studying and emulating how other humans interacted. But psychopaths are playing from a different set of rules than the rest of us. What crime fiction absolutely gets right is that women can be psychopaths too.

9. Myth: Certain types of mentally ill characters make for “unreliable narrators.” Crime fiction generally positions the story as “what happened.” But the truth is that we are all unreliable narrators in real life. Not just people with alcoholism, amnesia, or dissociative identity disorder. (You may recognize each of these three references to unreliable narrators as the “twist” from recent works of crime fiction, but I’m not going to spoil three great novels/films for you.) We all have reasons to remember through our own prism what “really” happened the summer after freshman year, or when our first relationship ended, or when we had an embarrassing incident. It’s part of what makes us human.

10. Myth: These myths don’t really matter. They’re just movies and books after all. When “Joker” — the first R-rated film to earn more than a billion dollars at the box office — was released in 2019, researchers randomized study participants to watch either “Joker” or “Terminator: Dark Fate.” After the participants watched “Joker,” scales they completed demonstrated higher levels of prejudice toward people with mental illness. Despite the film featuring superheroes and super villains in fictional Gotham City, there are real world implications that further stigmatize people with mental illness.

Almost half of us will experience symptoms of one mental illness or another during our lifetimes. But many fewer of us will seek treatment. Crime fiction, in films or novels, has an opportunity to correct the public’s misconceptions about mental illness rather than inflame them.

Susan Hatters Friedman, MD, is the Phillip Resnick Professor of Forensic Psychiatry at Case Western Reserve University in Cleveland, Ohio, where she is also professor of psychiatry, reproductive biology, pediatrics, and law (adj).