Study: High-potency cannabis may increase risk of psychosis

LONDON -- Regular marijuana users might want to think twice before lighting up another joint of "chronic" or "skunk" weed, a new study suggests.

According to a study of 780 people by King's College London's Psychiatry, Psychology and Neuroscience department, the risk of psychosis is five times higher for those who use high-potent cannabis every day compared to non-users.

The study, first analyzed by the BBC, claims that regular marijuana users who use a milder form of the drug with lower THC content are not associated with increased risk of psychosis, defined as delusions or hallucinations that can be present in certain psychiatric conditions. However, those who smoke high-potent cannabis were linked to 24 percent of new psychosis cases analyzed in the study.

Researchers fear that as high-potency cannabis becomes more easily found and use more widespread, we could see in increase in conditions such as schizophrenia and bipolar disorder.

"Compared with those who have never tried cannabis, users of high potency skunk-like cannabis had a threefold increase in risk of psychosis," Dr. Marta Di Forti, the lead author on the research, told the BBC.

The research was carried out over several years, and compared 410 patients aged 18-65 who reported a first episode of psychosis with 370 healthy participants in the same age range.

"Indeed skunk uses appears to contribute to 24% of cases of first episode psychosis in south London," the study's authors said.

Researchers said the findings underscore the need for increasing drug education, and a sharp reminder that no drug use comes without risks.

"Our finding show the importance of raising awareness among young people of the risks associated with the use of high-potency cannabis," the study's authors wrote. "The need for such public educations is emphasized by the worldwide trend of liberalization of the legal constraints on cannabis and the fact that high potency varieties are becoming much more widely available."

Recreational marijuana use is legal in Washington state.

To read an excerpt of the study, click here. For the BBC's story on the study, click here.