Reefer Madness

It looks like the makers of that old scare film might have been right:

By the end of the decade one in four new cases of schizophrenia could be triggered by smoking cannabis, scientists say.

Research has suggested that regular users of the drug are up to six times more likely to develop schizophrenia, although whether the drug is the direct cause remains disputed.

The Department of Health says it is now generally agreed among doctors that cannabis is an “important causal factor” in mental illness.

A study published in the journal Addiction predicts that, if the causal link between cannabis use and schizophrenia is accepted, rates of the illness will increase substantially by 2010, especially among young men.

The use of cannabis grew fourfold over the 30 years to 2002, and eighteenfold among under18s, the researchers say.

Such a boom in cannabis use could lead to increases in the number of new cases of schizophrenia of 29 per cent between 1990 and 2010.

Critics are still discussing the study with the voices in their heads.