Research links high-potency cannabis to psychosis and paranoia

Two new lines of research have strengthened concerns that increasingly potent cannabis products are linked to serious mental health harms and that people who begin using cannabis to self medicate are more likely to consume larger amounts and develop paranoia. A systematic review of nearly 100 studies found higher concentrations of delta 9 tetrahydrocannabinol, or THC, were associated with psychosis, schizophrenia and cannabis use disorder, while a large survey of more than 3,300 users in London reported that people who started using cannabis to relieve pain, anxiety or depression consumed more THC and reported higher levels of paranoia than those who began using for recreational reasons.

The systematic review analyzed 99 studies involving about 221,000 participants conducted between 1977 and 2023. Investigators categorized studies as therapeutic or nontherapeutic and set thresholds for high concentration products at greater than 5 milligrams per serving or about 10 percent THC, as well as products described as concentrates, shatter or dab. Among the nontherapeutic studies, 70 showed an unfavorable association between potent THC products and psychosis or schizophrenia, and 75...