Dagga tests mental health, study finds

The Daily Mail (week/commencing 28 Feb 2010)

Young people who use dagga are doubling their risk of developing psychotic symptoms experts warn. And mental health problems persist among those who continue using it compared with those who stop, according to international researchers.

Their study adds to mounting evidence that smoking dagga can trigger psychotic illnesses such as schizophrenia in vulnerable youngsters.

It appears to demolish counter-arguments that dagga does not cause symptoms of mental illness, or that some turn to the drug as a form of self-medication to deal with them.

The research also shows a link with psychosis at an early stage of use among young people who previously never experienced such symptoms. They include paranoid ideas, hallucinations, hearing voices or bizarre behaviour.

The study, by a team from Germany, the Netherlands and Britain, focused on more than 1900 volunteers aged 14 to 24 living in Germany. Those who had not previously used dagga but began to during the study had double the risk of developing psychotic symptoms, the study found. If they carried on using it, they were at an increased risk of psychotic experiences compared with those who did not. There was also no evidence that suffering psychotic symptoms was likely to result in people turning to dagga for relief.

Reporting on their findings in the British Medical Journal, the team concluded:

“Cannabis use precedes the onset of psychotic symptoms in individuals with no history of them.”

Dagga may also increase the risk of lasting harm to mental health by making such symptoms persist with continued use. Last month, Australian researchers found that dagga use accelerates the onset of full-blown mental illness almost three years earlier in people at risk.

Professor Robin Murray, of the Institute of Psychiatry in London, said of the latest study: “It is one of 10 prospective studies all pointing in this same direction. In short, it adds a further brick to the wall of evidence showing that use of traditional cannabis is a contributory cause of psychoses like schizophrenia.”