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Strong Cannabis Use Linked To Big Increase In Risk Of Pychosis PDF Print Email

Kings College London’s Institute of Psychiatry, Psychology and Neuroscience carried out research by studying 780 people which found that a almost a quarter (24%) of the new cases of psychosis were linked to smoking ‘skunk’ cannabis.


The research suggests users of ‘skunk-type’ cannabis are three times more at risk of developing psychosis and for those using it everyday the risk is five times higher than non-users.  The researchers also found that hashish, a milder solid resin type drug was not associated with increased risk of psychosis.

The condition psychosis includes delusions or hallucinations that can be present in certain psychiatric conditions such as schizophrenia and bipolar disorder.


The lead author of the researcha Di Forti said "Compared with those who had never tried cannabis, users of high potency skunk-like cannabis had a threefold increase in risk of psychosis, And added: "The results show that psychosis risk in cannabis users depends on both the frequency of use and cannabis potency."

The availability of skunk-like cannabis was becoming more widespread.


Skunk is a highly potent dense form of cannabis plant with an extremely strong smell.  It contains more THC - the main psychoactive ingredient - than other types of cannabis such as. Unlike skunk, hashish - cannabis resin - contains substantial quantities of another chemical called cannabidiol or CBD and research suggests this can act as an antidote to the THC, counteracting psychotic side effects.


Sir Robin Murray, professor of psychiatric research at King's, commented: "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."

The research was carried out over several years, comparing 410 patients aged 18-65 who reported a first episode of psychosis at a south London psychiatric hospital with 370 healthy participants within the same age range from the same area of London.

It will be published in the Lancet Psychiatry.


Rosanna O'Connor, director of alcohol, drugs and tobacco at Public Health England, responded: "No drug use is without risk as this report demonstrates.

"Anyone having problems with drug use should seek help from their local specialist drug services. It is important to remember that treatment for all types