The mainstream media was abuzz this week promoting an age-old claim: Smoking marijuana makes you crazy.
“Psychosis five times more likely for cannabis users: study,” a wire story from Agence France-Presse declared. The UK Mail on Sunday expressed similar alarm, declaring, “Scientists show cannabis TRIPLES psychosis risk.” Somewhat surprisingly, it was Fox News that took the most reserved approach, announcing “Smoking high-potency marijuana may cause psychiatric disorders.”
So what was the source of this latest round of sensational headlines? Writing in the February 18 edition of the British journal The Lancet Psychiatry, investigators assessed rates of cannabis use in a cohort of South London first-episode psychosis patients versus pot use frequency in a similar group selected from the general population. Authors reported that subjects with psychosis were more likely to recall having used “skunk-like cannabis” daily as compared to controls, whereas those participants who reported primarily consuming hashish possessed no elevated risk of having such a diagnosis. (Researchers defined so-called skunk marijuana as cannabis possessing THC concentrations above 15 percent. Of course, since cannabis is illegal in Britain and the weed obtained on the black market is not subject to analytical potency testing, it is unclear how subjects in the study—or its authors—knew whether participants were consuming supposed “high-potency” herb or just regular, plain old weed.)
Authors also acknowledged that nearly half of patients with first-episode psychosis reported having smoked 100 cigarettes or more. These patients were also more likely to be black and were less likely to have completed high school compared to controls, though, predictably, none of these observed associations triggered international headlines.