SKUNK INCURS 18 TIMES THE RISK
People who smoke skunk, the extra strong cannabis grown in hothouse conditions, are 18 times more likely to develop psychosis that those who take the milder forms such as hash (cannabis resin), states a study presented to the Annual Meeting of the Royal College of Psychiatrists [3 July 2008].
Psychiatrist Dr Marta Di Forti, as part of the Genetics and Psychosis Study led by Professor Robin Murray, compared the pattern of cannabis use between 112 patients with first-episode psychosis and 75 healthy ‘controls’ screened for psychosis, both groups from south east London. They found that people who had a psychotic episode were twice as likely to have used cannabis for longer, three times more likely to have used it every day and 18 times more likely to use skunk.
The cannabis plant is "a rich treasure trove of pharmacology" and contains 60 cannabinoid molecules, said Dr Paul Morrison, a senior researcher working with Professor Murray. The one which attracts most publicity is THC Delta-9- tetrahydrocannabinol, responsible for the psychotic symptoms and the cognitive deficits induced by cannabis.
But cannabis it also contains another molecule, CBD or cannabidiol, which seems to protect users from the psychosis and impaired cognition induced by TCH. CBD seems to counteract the effect of THC.
The potency of THC in cannabis has increased steadily over the past decade due to higher concentrations of the drug and its formulation, delegates at the Annual Meeting heard (Data available in a recent paper by Dr Potter, January 2008 Journal of Forensic Science).
In 1995, skunk had 6% THC; now that figure is nearer 16-18%. Skunk contains no or very little CBD, so there is nothing to protect users against its power.
Dr Di Forti used an analogy comparing users of cannabis to drinkers. Like the drinker who starts off on half a pint of lager and ends up drinking a bottle of vodka a day, cannabis users might start with a weekly joint of hash or grass and graduate to smoking skunk every day, she said.
Because of the difference in strengths of cannabis formulations, Dr Di Forti urged psychiatrists to question their patients on their drug habits in a more detailed way. "We should have more data on cannabis exposure. We should take a cannabis history in a more detailed way like we do when we take a history of cigarettes smoking to establish risk of lung cancer. But it would be naive to say that smoking a joint is safe as we do not have enough data to reach such conclusion,” she recommended.
Annual Meeting of the Royal College of Psychiatrists, Imperial College, London, 1 – 4 July 2008.