Cannabis, Skunk and Psychosis

Researchers at the Institute of Psychiatry in London have published a study looking at the impact of cannabis use on psychosis, which has been a hot political topic in recent years. The research had a specific focus on high-potency, “skunk” varieties of the drug. It compared patients admitted to hospital with first episodes of psychosis with a group of people from the nearby community. There were no differences between the two groups in terms of the proportions of their ever having used cannabis or age at first use. However, amongst the cannabis users, patients with psychosis were nearly seven times as likely to smoke the high potency skunk varieties as the second group. Researchers suggest that the apparent greater risk involved in the use of skunk is linked to its higher THC content and low cannabidiol (CBD) content, two of the main chemicals in the drug. In the traditional resin hash preferred by the control group, levels of THC averaged at 3.4%, with similar levels of cannabidiol. Skunk, by contrast, contains 12-18% THC and 1.5% CBD. It appears that cannabidiol may help to protect against psychosis.

The lead researcher, Dr Di Forti said, “Our study is the first to demonstrate that the risk of psychosis is much greater among people who are frequent cannabis users, especially among those using skunk, rather than among occasional users of traditional hash.” It is unclear whether the researchers are suggesting that heavy skunk use causes psychosis, or whether there is merely a correlation, in which case it may be that those already troubled by symptoms of mental illness are using stronger varieties of cannabis to alleviate symptoms. What is clear is that production of the skunk varieties has been driven by commercial factors in an unregulated market where profit is the sole governing principle.