Cannabis linked to psychosis cases

A powerful "skunk-like" cannabis is associated with one in four new cases of psychosis, a study has found.

Scientists at King's College London also found the potent form of the Class B drug led to a three-times higher risk of psychosis in casual users, rising to a five-fold risk in those who used it every day.

The findings of the six-year study, published in the Lancet Psychiatry journal, suggest strong forms of cannabis can lead to serious mental illness, the researchers said, as they called for greater public awareness.

But it comes as a US neuroscientist suggested long-term recreational cannabis use has no significant association with long-term mental decline.

Sir Robin Murray, professor of psychiatric research at the Institute of Psychiatry, Psychology and Neuroscience IoPPN at King's and senior researcher on the study, said: " It is now well known that use of cannabis increases the risk of psychosis. However, sceptics still claim that this is not an important cause of schizophrenia-like psychosis.

"This paper suggests that we could prevent almost one quarter of cases of psychosis if no-one smoked high potency cannabis. This could save young patients a lot of suffering and the NHS a lot of money."

While skunk was associated with psychotic episodes, the milder form of cannabis known as hash had no such link, the scientists said.

Dr Marta Di Forti, lead author on the research, said: " The results show that psychosis risk in cannabis users depends on both the frequency of use and cannabis potency. The use of hash was not associated with increased risk of psychosis.

"As with smoking tobacco and drinking alcohol you need a clear public message.

"When a GP or psychiatrist asks if a patient uses cannabis it's not helpful; it's like asking whether someone drinks. As with alcohol, the relevant questions are how often and what type of cannabis. This gives more information about whether the user is at risk of mental health problems; awareness needs to increase for this to happen."

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Source: Belfast Telegraph, 16/02/15