Sci&Tech Writer Madison Harding-White unpicks the science behind Joaquin Phoenix’s ‘Joker’

A Neuroscience graduate interested psychology, debate and sustainable lifestyles.
Images by Hans Renier

Many of us are familiar with the classic comic book Joker: a fantastical, crazed villain whose violent behaviour and shocking appearance originated from his submersion in a vat of fictitious chemicals. However, in his latest origin story- 2019’s Joker– we are newly presented with a disturbing tale of physical abuse, injury, social isolation and mental illness. Many agree this film was unsettling, but less so the gory murders, and more the strong underpinnings in criminal psychology which makes this film so realistic and challenging to watch.

We are newly presented with a disturbing tale of physical abuse, injury, social isolation and mental illness

One striking factor alluded as contributing to the Joker’s murderous crimes was psychosis, portrayed in both the Joker and his mother. Whilst the majority suffering from psychosis do not commit crime, some research does present the illness as a potential risk factor.  Recent research from Jon Volavka and colleagues demonstrated that when presented with life stressors including exposure to violence and self-injury – stressors the Joker is depicted as experiencing in the film – participants with schizophrenia were most likely to themselves display violence the following week when compared to those with bipolar disorder and participants without mental illness. This was theorised to be mediated by the stress triggered by these events causing an increased release of glucocorticoids, steroids which contribute to the fight or flight response. Release of glucocorticoids is thought to make the individual more sensitive to aggression provoking stimuli. Furthermore, research has also shown that risk for violent offending is increased when an individual is exposed to parental mental illness, as well as childhood maltreatment, factors both experienced by the Joker. 

Further, we are presented with a character who is visibly malnourished, a cigarette never far from his mouth. In research from Jinghong and Raine, both macromalnutrition (such as protein deficiency) and micromalnutrition of minerals such as iron and zinc were linked as contributors to the development of childhood Conduct Disorder, symptoms of which can include severe aggression which can continue into adulthood. Furthermore, nicotine withdrawal has been consistently linked with increased anger, irritability, physical aggression and a reduction in social functioning.  Unfortunately for our character, the Joker is also said to have suffered a traumatic head injury as a child- a condition which has also been linked to an increase in the severity and prevalence of violent crime. This injury was also said to be the cause of his uncontrollable laughing- a feature visibly causing him to be socially rejected and mocked. Being ostracised has too been linked to aggression, specifically when an individual feels it may improve their negative affect, a concept poignant at the end of the film.

It’s important to remember that risk does not equate to certainty or remove the aspect of personal choice

The inclusion and accumulation of these scientifically researched factors in the creation of this Joker has undeniably resulted in a well written, chillingly familiar character who is both fascinating and upsetting to watch. However, whilst research investigating the risk factors which can cause individuals to commit violent crime is compelling, it’s important to remember that risk does not equate to certainty or remove the aspect of personal choice which, unless insanity is ruled, is always involved. Cinematically, we can hope that future superhero films too take a scientific approach in order to compete with Joker’s sad and jarring story.

More on Joker:

Review: Joker

Red Carpet: Joaquin Phoenix

Mad Men, Bad Men: Our Obsession with the Toxic Man in Cinema