A person suffering from shared psychotic disorder—also known as shared psychosis and originally known as folie á deux (literally French for "madness of two" but often called "folly of two" in English)—buys into someone else's psychosis and takes on, in part or even in whole, the other's delusional thinking (American Psychiatric Association, 2022). With nothing in the traditional depictions of the character Dr. Harleen Quinzel's history to suggest that she was psychotic before her internship at Arkham Asylum (or residency depending on who writes the story) before the Joker manipulates her and inspires her to become the criminal Harley Quinn, this diagnosis seems possible if she's really psychotic.
In most stories, she does not seem to hallucinate or show other persistent symptoms that might suggest she has become schizophrenic. Admittedly, it can be difficult to tell whether or not she is simply joking about hearing voices in her head, as she does during her big-screen debut in the first Suicide Squad movie (2016). Considering that this only comes up in a moment when perfectly timed to unnerve others and does not become an issue at any other point during the film, she does not actually seem to hear voices. Surreal imagery such as floating flowers throughout her violence in its sequel, the similarly named The Suicide Squad (2021), more strongly suggests hallucination. Then again, it might simply qualify as an artistic representation of vivid imagination. A distorted point of view and willful blindness to some things that may seem obvious to others, just as the Joker's gaslighting, do not in and of themselves mean she's psychotic. It's a matter of severity and duration of the reality distortion. That she does eventually get convicted and sentenced, then offered an opportunity to work off that sentence, indicates that the law finally deems her legally sane.
Why is the new movie that features Harley named after a psychotic disorder?
In 2019's motion picture titled simply Joker, Joaquin Phoenix played Arthur Fleck, a demonstrably disturbed and sometimes violent man who wants to be called, "Joker"—not the Joker in this case, just Joker. Filmmaker Todd Phillips and his writers carefully researched real mental illness while also making sure they did not neatly depict Joker as fitting one specific condition. Unlike other Jokers in comics and film, Fleck is definitively shown to suffer gross distortions of reality: hallucinations such as seeing people who are not there, and delusions such as believing he has an ongoing relationship when he does not. His compulsive bursts of laughter would be unrelated to his psychosis if a traumatic brain injury has caused pseudobulbar affect, but the laughter may indeed be a symptom of his psychosis if he does not have the neurological problem as he claims (Merchán-del-Hierro and colleagues, 2021; Skryabin, 2021).
Given his hallucinations and delusions, this Joker is psychotic, out of touch with reality at least when he goes unmedicated. Once moviegoers discover this aspect of the film, they reassess the movie they've been watching to contemplate which aspects are "real" within the context of the story and which Fleck's psychotic mind has conjured. In this, Fleck is an unusual variation of the Joker character, to be sure, but then again, the Joker has changed repeatedly throughout the characters' various incarnations and chaotic history. Like other modern versions, though, he seeks narcissistic revenge, and self-absorbed aggression against the world out of frustration that it has not given him what he wants (Machado and colleagues, 2021).
The sequel Joker: Folie á Deux adds the Joker's girlfriend Harley Quinn, who goes by the name Lee this time. First introduced in Batman: The Animated Series, Dr. Harleen Quinzel has been depicted as an Arkham Asylum psychiatrist who is already fascinated by dangerous criminals and falls in love with the Joker. He tells many lies and plays on her emotions, manipulating her, but then it is she who actively chooses to become a costumed crook and break him out of Arkham. Some later versions reduce Quinzel's agency in becoming criminal Harley Quinn, but then the Harley Quinn animated series gives it back to her. In the Joker sequel, Lee takes charge. Upon seeing Fleck murder a talk show host on live television, she grows fascinated with him and feels she has found a kindred spirit. As he awaits his trial two years later in a medicated, sedated state, he does not seem particularly active and expressive, but through music, she brings him out of his shell. Fleck may be psychotic, but what is she? Rather than a psychiatric condition in which one person's "madness" inspires it in another, might this be a "folly of two" in which each person's psychosis promotes it in the other? (If she really exists in the context of the story, of course. Is she a psychiatrist administering music therapy, a fellow mental hospital patient, or a figment of Fleck's imagination?)
The DSM-5 no longer lists shared psychosis as a distinct diagnostic term, although there are professionals who find it useful and continue to use it. Folie á deux has gone through numerous names (folie á deux, Lasègue–Falret syndrome, shared paranoia, shared psychosis, the psychosis of association, induced psychosis, induced delusional disorder) as professionals have learned more and reconsidered it over the years (American Psychiatric Association, 1980, 1994; Arnone and colleagues, 2006; Dewhurst and John, 1956; World Health Organization, 1992). In the American Psychiatric Association's current diagnostic manual (APA, 2013; 2022), it would be identified as "delusional symptoms in the partner of an individual with delusional disorder," under Other Specified Schizophrenia Spectrum and Other Psychotic Disorders: "In the context of a relationship, the delusional material from the dominant partner provides content for delusional belief by the individual who may not otherwise entirely meet criteria for delusional disorder" (APA, 2013, p. 122).
No Joker is merely delusional, though, and the film sequel may blur the lines concerning who really counts as the dominant partner at any given time and how their dominance-submission interplay really works.
THE BASICS