People Who Smoke Skunk Are 18 Times More Likely
To Develop Psychosis
July 3, 2008
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), a new study has found.
The study, which was carried out at the Institute of Psychiatry and presented
this week to delegates at the Annual Meeting of the Royal College of
Psychiatrists, looked at the links between cannabis use of psychosis.
Psychiatrist Dr Marta Di Forti, as part of the GAP (Genetics and Psychosis)
Study led by Prof 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 Prof Murray and presenting at the meeting as well. The one that has
attracted the most publicity is THC Delta-9- tetrahydrocannabinol, which is
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 last 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 per cent THC; now that figure is nearer 16 -18 per cent.
Skunk not contains only high levels of THC, but contains no or very little CBD,
so there is nothing to protect users against its power.
In contrast with skunk, hash contains much less THC and an almost equal amount
of CBD, which might contributes to further reduce the potency of its adverse
effect. For example, Savitex, the cannabis drug, used to treat multiple
sclerosis, has equal amounts of both THC and CBD.
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 said.
Reference
The Annual Meeting of the Royal College of Psychiatrists, Imperial College,
London, 1 - 4 July 2008
Royal College
of Psychiatrists
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