People suffering from mental illness are almost five times more likely to be victims of murder than the general population, researchers have found .

The popular myth of the “mad axeman” on the loose has created an impression that mentally ill people are dangerous which may expose them to greater risk, they say.

Although murders committed by mentally ill people have been widely studied, much less attention has been given to murders of them.

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Swedish and American researchers examined 615 murders in Sweden between 2001 and 2008 and found in more than one in five (22 per cent) the victim had been mentally ill.

It is well known that people with mental illness are more at risk of suicide and accidental death. But this is the first time they have been shown to be at increased risk of murder.

The risk of dying by murder was highest among those whose mental illness was complicated by drug abuse. But it was also increased in those with personality disorders, depression, anxiety and schizophrenia.

The researchers blame, in part, the common perception that people with mental disorders are "unpredictable" or "dangerous". This, they say, creates "feelings of uneasiness, fear and a desire for social distance and may increase the risk of victimisation."

Mentally ill people are also more likely to live in deprived neighbourhoods and may be less aware of risks to their safety owing to their illness.

The researchers based their findings on the entire adult Swedish population of more than 7 million and adjusted their results for sex, age, education, marital status, employment and income.

The findings, published in The Lancet, have implications for the assessment of mentally ill people, say Roger Webb and colleagues from the University of Manchester in an accompanying editorial.

Doctors should asses their risk of being victims of violence, abuse and bullying, as well as their risk of committing it. "Anti-stigma campaigns among the public should aim to counter fear of mentally ill people with sympathy for the risks they face."