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Strong cannabis users 5 times more likely to develop psychosis

By Stephen Morgan     Mar 3, 2015 in Lifestyle
A British study has found that people who consume the new stronger forms of cannabis are 5 times more likely to develop psychotic disorders than non-users are.
The study was carried out by researchers from the Institute of Psychiatry, Psychology & Neuroscience at King’s College London and was published in the journal, Lancet Psychiatry.
It took place in south London over a period of six years and involved almost 800 people. Of these 410 were suffering from first time psychosis, including schizophrenia and bi-polar disorder.
It surveyed people who smoked ordinary cannabis, those who smoked "skunk" — which a very strong form of the drug — and those who smoked nothing at all.
The data gathered showed that people who used skunk cannabis were at severe risk of developing psychotic disorders. According to the findings, those who used skunk generally had three times more chance of developing psychosis than non-users, and for those who took skunk everyday there was a five fold risk.
The results on skunk are particularly important, because it is the main form of cannabis which is now smoked in London and elsewhere in the UK. Moreover, newer varieties of the super hash are arriving on the streets all the time.
Discovery News quotes the lead author of the study, Marta Di Forti, who stated that,
“Compared with those who had never tried cannabis, users of high potency skunk-like cannabis had a threefold increase in risk of psychosis.”
“The risk to those who use every day was even higher — a fivefold increase compared to people who never use,” she added.
Worryingly, with regard to skunk, Dr Di Forti told BBC Radio 4: "In London, it's very difficult to find anything else."
According to the Telegraph,
"The finding suggests that about 60,000 people in Britain are currently living with conditions involving hallucinations and paranoid episodes brought on by abuse of high-potency cannabis, known as skunk, and more than 300,000 people who have smoked skunk will experience such problems in their lifetime."
The Independent reports that in the study,
"More than half of the psychosis patients surveyed said they smoked skunk to some extent (53%) whilst skunk smokers only represented 29% of the non-psychotic control group."
Robin Murray, a professor of psychiatric research at King’s College London and a senior member of the research team, suggested that skunk could account for a quarter of all new cases of psychotic illness.
“This paper suggests that we could prevent almost one-quarter of cases of psychosis if no one smoked high potency cannabis,” he said.
However, the report also showed that those who smoked ordinary hash were no more likely to develop psychosis than people who touched neither. Normal hash has even been shown to have properties which could counteract psychotic disorders.
The BBC explains the difference between the two forms of cannabis, which lies behind the contrast in the results,
"Skunk contains more THC - the main psychoactive ingredient - than other types of cannabis."
"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."
Tetrahydrocannabinol (or THC) levels in skunk are about 15 percent and only around four percent in normal hash.
As with all research, there is plenty of room for criticism and hype, but this study is one of the first which shows the divergent effects of different strengths and types of cannabis in this way.
More about Cannabis, Strong, Skunk, Psychosis, Risk