Cannabis linked to violence in young men

Young men who take cannabis are more violent, researchers suggest

Young men who take cannabis are five times as likely to be violent as those who do not take it, research has revealed.

The drug is more usually associated with mellow moods.

But the scientists who carried out the study told BBC News Online the link to violence was not due to any effects of the drug - instead it was because users are involved in the illegal drug market.

New Zealand scientists have carried out the first study into the overlap between mental disorders and violence in young men.

The cannabis users had an earlier history of conduct disorders as adolescents

Dr Louise Arseneault

Almost 1,000 babies born between April 1972 and March 1973. in Dunedin, New Zealand were studied as they grew up.

When they were studied at 21, 34% of the young men who had a cannabis habit had a conviction for violence or had committed violent behaviour in the previous year.

The research was presented to the Royal College of Psychiatrists' annual meeting in London.

Drug market

Dr Louise Arseneault, from the Institute of Psychiatry in London, told BBC News Online: "The cannabis users had an earlier history of conduct disorders as adolescents. Violence was associated with their involvement in the drug market."

There was also a three-fold risk increase associated with men suffering from schizophrenia or dependent on alcohol.

Of the total sample, 40% had mental disorders and were five times more likely to be violent than people without mental conditions.

Dr Arseneault said: "There is a substantial minority of young adults with specific mental disorders who are responsible for a substantial proportion of violence in the community."

She said people with at least one of the disorders constituted a fifth of the sample, but accounted for more than half the convictions for violence.

"People with two of these disorders have an increased risk for violence eight to 18 times greater than that for people with no disorders," she added.

Dr Arseneault added: "Not all mentally-ill individuals engage in violence. The link is limited to three groups - those dependent on alcohol, those dependent on cannabis, and adults with schizophrenia."