Bipolar disorder 'not to blame for violent behaviour'
People with a severe mental illness are no more likely to be violent than anyone else - unless they abuse drugs or alcohol, a study has suggested.
The relationship between bipolar disorder and violence largely came down to substance abuse, researchers said..
The study compared the behaviour of people with the disorder with their siblings and the wider population.
One of the authors said it was probably more dangerous to walk past a pub at night than a mental health hospital.
The study, led by Oxford University's Department of Psychiatry, examined the lives and behaviour of 3,700 people in Sweden who had been diagnosed with bipolar disorder, commonly known as manic depression.
The disorder leads to sudden and unpredictable mood swings which are more severe than the normal ups and downs of life.
The team, led by consultant forensic psychiatrist Dr Seena Fazel, wanted to examine the public perception that there is a link between the disorder and violent crime.
They did this by comparing the experiences of the patients with some 4,000 siblings of people with bipolar disorder - and a further group of 37,000 people selected from the general population.
The research, published in the Archives of General Psychiatry, found that the rates of violent crime among people who were mentally ill and abused substances were no different to those among the general population who abused substances.
In each group, the rate of violent crime was between six and seven times higher than in the general population.
"Most of the relationship between violent crime and serious mental illness can be explained by alcohol and substance abuse," said Dr Fazel.
"That tends to be the thing that mediates the link between violence and the illness."
He said that if the substance abuse was taken away, the illness itself had a "minimal" or non-existent role in violence.
Dr Fazel said: "It's probably more dangerous walking outside a pub on a late night than walking outside a hospital where patients have been released"
The study said that people with bipolar disorder were 10 times more likely to abuse drugs or alcohol than those in the overall population because they tended to turn to substances to counter the effects of their medication or to get other relief from their symptoms.
A previous paper on schizophrenia, written by several of the same researchers, came to similar findings.
The findings of both studies support the view of mental health charities who argue that the stigma attached to illnesses is not justified by medical evidence.
In 2009 the BBC joined forces with mental health charities for a story line in which one of the characters in the Eastenders soap came to terms with bipolar disorder.
Paul Farmer, chief executive of the mental health charity Mind, said the research would reassure people with severe illnesses such as bipolar disorder and schizophrenia.
"The link between mental illness and violence is often grossly exaggerated when in fact people with mental health problems are far more likely to be the victims of crime than the perpetrators
"This kind of stigma damages lives," he said.
The charity Sane said it was "surprised" the research appeared to overlook the "realities of severe mental illness".
Its chief executive Marjorie Wallace said: "We accept that alcohol and drug abuse can exacerbate the more acute symptoms and that such abuse is more widely responsible for criminal acts.
"We also accept that the majority of people with mental illness are never violent and the chances of a member of the public being attacked at random extremely rare.
"However, we do not believe it is helpful to underplay the extreme pain, paranoia and denial of symptoms such as command voices which those with psychosis can experience and which may trigger damaging behaviour."