Cannabis products with increasingly high concentrations of THC, the main psychoactive compound in cannabis, have become more and more available to the public as cannabis laws have loosened. In this study, researchers set out to understand the effects of high-concentration THC products on different mental health outcomes.
To do so, they analyzed 99 studies including over 221,000 participants. Just over 4 in 10 of the studies were randomized trials, and 47% were observational studies. High-concentration THC was defined as quantities greater than 5 mg, exceeding 10% THC per serving, or being labeled as ‘high potency concentrate’, ‘shatter’, or ‘dab’. Outcomes included anxiety, depression, psychosis or schizophrenia, and cannabis use disorder (CUD). Over 95% of the studies had a moderate or high risk of bias.
Ultimately, the researchers found that among studies not testing for therapeutic effects, high-concentration THC products were consistently linked with psychosis, schizophrenia, and CUD. None of the therapeutic studies reported favourable effects on psychosis or schizophrenia.
Meanwhile, around half of nontherapeutic studies for anxiety and depression found unfavorable links- especially among healthy individuals. Among therapeutic studies, around half found benefits for anxiety and depression, whereas 24% and 30% found unfavorable links. Use of high-concentration THC for medical reasons, like cancer or neurologic conditions, was more likely to yield positive effects on anxiety.
“Although there may be some benefits for anxiety in specific medical contexts, the evidence is weak and inconsistent. More research is needed to understand the long-term effects. Patients should be cautious with high-concentration products, especially if they have a history of mental health problems,” reported a patient summary of the study in the Annals of Internal Medicine.
Sources: EurekAlert, Annals of Internal Medicine, Summary for Patients, Annals of Internal Medicine
