As junior doctors who work on acute inpatient psychiatric wards, serious mental illness is our daily reality. We have, therefore, watched the controversies around Todd Phillips’s Joker – in which Joaquin Phoenix plays a troubled loner who turns to violence – with professional interest.

The film’s dominance in the debate about portrayals of mental illness in the movies comes at a curious time. Recently, we’ve witnessed great leaps of awareness about relatively common mental-health issues such as depression and anxiety, and with that awareness, increasing dismissal of the sort of unhelpful prejudices that used to surround them. These are now readily discussed without shame and often represented in the media with a well-informed grasp of the facts, thanks to effective information campaigns.

However, severe mental health conditions, such as psychotic illnesses, remain shrouded in stigma and are consistently misrepresented and misunderstood. Portrayals of mental illness in film can perpetuate unfounded stereotypes and spread misinformation. One of the more toxic ideas that Joker subscribes to is the hackneyed association between serious mental illness and extreme violence. The notion that mental deterioration necessarily leads to violence against others – implied by the juxtaposition of Phoenix’s character Arthur stopping his medication with his increasingly frequent acts of violence – is not only misinformed but further amplifies stigma and fear.

Studies show this association is exaggerated and people with severe mental illness are more vulnerable to violence from others than the general population. Interesting, then, that Joker’s earnest attempt to create an empathetic character with mental illness – who writes: “The worst part of having a mental illness is people expect you to behave as if you don’t” – contributes to the very prejudice that Arthur longs to evade.

Arthur’s supposed loss of grip on reality is suggested by a peppering of nods to psychotic symptoms: delusional ideas of a grandiose nature (“I am an undiscovered comedic genius”) and hallucinations of his neighbour – which are confirmed by his eventual admission to a psychiatric institution. This restoration of order via Arkham Asylum affirms the overarching inference of the film: Arthur’s descent into violence and destruction is triggered by his mental deterioration. The result of this is to – disappointingly – remove Arthur’s agency and divert attention from a potentially more stimulating conversation about wealth inequality and its responsibility for societal collapse.

Misinformed … One Flew Over the Cuckoo’s Nest, starring Jack Nicholson. Photograph: Allstar/United Artists

We wouldn’t want to get bogged down in labels, but the psychopathology Arthur inhabits is foggy at best: his apparent lack of disordered thinking means the attempt to illustrate psychosis is half formed. He also displays traits of narcissism and depression. This diagnostic vagueness may create a more relatable character that reflects the pain of any psychiatric illness; but it gives the impression that many disorders have been squashed into a plot device. In the end, it undermines Phoenix’s hypnotic performance and Joker’s sincere attempts to explore the interaction between poverty, inequality and social isolation.

Arthur’s chilling quirk – his bursts of incongruous and uncontrolled laughter – is no laughing matter either. Presumably, he suffers from the neurological condition pseudobulbar affect – also known as “emotional incontinence” – perhaps caused by his childhood head trauma. Joker may make an attempt to unpick the difference between the psychiatric and the neurological – between a mental illness and a medical disorder – but it runs the risk of conflating the two with a haunting, stigmatising and problematic image. Whether intentionally or not, Arthur comes across as a hysterically laughing supervillain, stereotypically “mad” to the untrained eye; a murderous clown laughing alone on a bus.

Cinematic depictions of mental illness – most infamously, One Flew Over the Cuckoo’s Nest – have profound and lasting implications in the real world. It is widely acknowledged within psychiatry that Cuckoo’s Nest led to inappropriate levels of suspicion and misinformation regarding electro-convulsive therapy, and may have meant many people did not receive treatment that is proved and effective. All this due to a single film’s misinformed presentation.

Films have the power to perpetuate stigma and fear, which is why the misrepresentation of severe mental illness in Joker should not be dismissed lightly.