Cannabis Harms Mental Health, Scientists Warn

New evidence showing how cannabis disrupts brain function will be presented at an international conference in London this week. Some of the world’s top scientists will gather at the Institute of Psychiatry to warn of the drug’s dangers and how it can precipitate psychosis and schizophrenia.

“We are very close to finding a causal link between cannabis and mental illness – all evidence is pointing in that direction,” Dr Zerrin Atakan, one of the conference organisers, told The Independent on Sunday.

Dr Atakan has been involved in the first study into how cannabis affects the brain, and she says that it has a destabilising influence: “There is a disturbance of the area governing thoughts and emotions and this seems to be related to temporary psychotic symptoms suffered by some of the people that took part.”

New images from MRI scans will show how those given the cannabis compound THC had a significantly reduced activity in the frontal lobe – a part of the brain responsible for co-ordination and emotional behaviour.

Philip McGuire, professor of psychiatry and cognitive neuroscience at the Institute of Psychiatry, who will be presenting the findings, said: “What hasn’t been known up to now is how THC has produced psychotic symptoms. This research is about linking what we already knew of the effects of cannabis to the mechanism underlying them in the brain.”

Doctors say that it is impossible to predict with certainty which people might be vulnerable to psychosis and schizophrenia, aside from those with a family history of such problems.

All this comes as a ferocious debate continues over the mental health risks of skunk – a potent new form of the drug – first reported in this newspaper last month. More than 22,000 people in Britain needed treatment for cannabis use in 2006, and emergency hospital admissions have doubled in the past five years.

A new campaigning group, Talking About Cannabis, is being launched in London this Friday, and will lobby the Government to tackle the crisis.