Skunk linked with psychosis

Smokers of skunk are 18 times more likely to develop psychosis that those who take the milder forms of cannabis such as hash (resin).

The study compared cannabis use of 112 patients with first episode psychosis (loss of contact with reality, hallucinations, delusions etc.) and 75 healthy 'controls' - both groups were from south east London. 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 contains 60 cannabinoid molecules. 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.

CBD may make the difference

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.

In 1995, skunk had 6% THC; now that figure is nearer 16 or 18%. 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.

Because of the difference in strengths of cannabis formulations, delegates to the Royal College of Psychiatrists AGM were told to question their patients on their drug habits in a more detailed way.