March 2, 2011

Link Between Cannabis Use, Psychosis Established

Teenagers and young adults who use cannabis are more likely to suffer psychotic symptoms, according to a new study published Tuesday on the British Medical Journal (BMJ) website.

In their study, Professor Jim van Os from Maastricht University in the Netherlands and his colleagues studied a random sample of 1,923 adolescents and young adults between the ages of 14 to 24 years, following them over a period of 10 years to gauge the correlation between cannabis use and the incidence and persistence of psychotic symptoms, the BMJ said in a March 1 press release.

Those who had reported prior use of cannabis or pre-existing psychotic symptoms were excluded from the study, as van Os and his team were focusing on the relationship between new use of the world's most commonly consumed illicit drug and the signs of the mental illness.

Each of the subjects was assessed for both cannabis use and psychotic symptoms three times during the study period, at an average interval of four years apart, according to the BMJ.

The researchers discovered that "incident cannabis use almost doubled the risk of later incident psychotic symptoms, even after accounting for factors such as age, sex, socioeconomic status, use of other drugs, and other psychiatric diagnoses," the press release said, adding that "continued use of cannabis over the study period increased the risk of persistent psychotic symptoms."

While Reuters reporter Kate Kelland points out that experts are still not sure whether or not the link between the drug and the psychotic symptoms is causal, Robin Murray, a professor of psychiatric research at the King's College London Institute of Psychiatry who was not involved with the study, told the AFP that the results did, in fact, back-up such claims.

"This study adds incremental information to the already fairly solid evidence that continued use of cannabis increases risk of psychotic symptoms and psychotic illness," he said. "In short, this study adds a further brick to the wall of evidence showing that use of traditional cannabis is a contributory cause of psychoses like schizophrenia."


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