All too often they are rambling derelicts howling at the moon. Or violent psychopaths with murderous intent.
Historically, the way mental illness has been portrayed on the big screen and on television did little to help remove stigma. But cinematic depictions of the mentally ill as hopeless figures of fear, pity or ridicule are slowly being challenged.
While, once, movies such as Psycho and One Flew Over The Cuckoo's Nest perpetuated negative stereotypes, a new wave of offerings including Hollywood blockbuster Silver Linings Playbook and TV comedy-drama United States of Tara moved beyond crude caricatures.
Next week, filmmakers, health professionals and people living with mental illness will convene at a symposium in Melbourne to explore in greater depth how positive on-screen portrayals can improve lives.
The two-day event at the University of Melbourne - Try Walking in My Shoes - will look at how empathy can be boosted and community awareness raised by responsible, accurate depictions of what life is like for the mentally ill.
It will also explore how negative portrayals can heighten public fear and ignorance.
''The most obvious and probably most damaging stereotype is the psycho killer and that idea that someone who's mentally ill is also violent,'' said Fincina Hopgood, co-convener of the symposium, which is presented by the Dax Centre and the Australian Research Council Centre of Excellence for the History of Emotions.
Dr Hopgood said that research showed Hollywood portrayals of deranged, violent killers could feed into public fear of those with psychiatric conditions, despite those with a mental illness being more likely to be victims of rather than perpetrators of crime.
''Hitchcock's Psycho has a lot to answer for because it very much links Norman Bates' violence to his psychically damaged relationship with his mother,'' she said. ''Even in soap operas, there's always been that stereotype of the violent character who's living next door who has a mental illness.''
She said other unhelpful stereotypes were the ''comic loony'', such as Jim Carrey's character in the comedy Me, Myself & Irene, in which he plays a man with a split personality, and the ''idiot savant'' as depicted by Dustin Hoffman in Rain Man.
Among the Australian films to be discussed at the symposium will be The Sunnyboy, a documentary that has been widely praised by mental health experts for its sensitive, compelling depiction of the life of Sunnyboys singer Jeremy Oxley and his battle with schizophrenia.
Director Kaye Harrison said she felt a responsibility to portray mental illness accurately.
''I'd like it known that it is possible to make documentaries, which are entertaining and engaging, which do have integrity in terms of representing mental illness,'' she said.
Diahann Lombardozzi will present her film Hypothesis, about her 12-year journey with bipolar disorder. The 44-year-old mother-of-two from Kew said she hoped to challenge cinematic depictions of the condition, which often portrayed people as dysfunctional and never able to recover.
''I've managed to have a career, a family, even care for my grandmother and father but, in the meantime, there's always a period where I get a little bit overworked and, before I know it, I crash and have a bit of an episode,'' she said. ''But the positive thing is, over the period of my life, my episodes have become less frequent and they haven't been as severe.
''It's important that people know that you can have an active and very productive and rewarding life even with a mental illness.''
Stephen Macfarlane, director of aged psychiatry at Alfred Health and the Caulfield Hospital, will examine the on-screen depiction of dementia.
''In The Simpsons, the single negative portrayal of somebody like Grandpa Simpson can set people with dementia up to be perceived as figures of fun who aren't to be taken seriously - they're an annoyance and it trivialises an illness that's actually a major global problem,'' he said.
''It's evolved over the decades, and there's a vast increase in the number of sympathetic portrayals, but there's still a long way to go in terms of those being outweighed by overwhelming negative depictions of those with mental illness.''
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