A comprehensive analysis of over 2,500 studies shows that medical cannabis has strong evidence for only a few specific uses, despite widespread public belief in its broader effectiveness. Led by UCLA Health researchers, the review highlights gaps between perceptions and scientific proof for conditions like chronic pain and anxiety. It also identifies potential risks, particularly for adolescents and daily users.
Researchers from UCLA Health, along with collaborators from Harvard, UC San Francisco, Washington University School of Medicine, and New York University, conducted a major review published in JAMA in 2025. The study examined more than 2,500 scientific papers from January 2010 to September 2025, prioritizing over 120 based on sample size, recency, relevance, and health conditions covered. This effort comes amid rising interest in cannabis and CBD, with a 2018 survey indicating that 27% of adults in the U.S. and Canada used them for pain, anxiety, or sleep issues.
The review concludes that only FDA-approved pharmaceutical-grade cannabinoid products show clear benefits. These are confined to treating HIV/AIDS-related appetite loss, chemotherapy-induced nausea and vomiting, and severe pediatric seizure disorders like Dravet syndrome and Lennox-Gastaut syndrome. For common uses such as chronic pain, anxiety, and insomnia—cited by over half of medical cannabis users—evidence remains weak or insufficient. Clinical guidelines do not endorse cannabis-based treatments as first-line options for pain management.
Safety concerns are notable. In adolescents, high-potency cannabis links to elevated psychotic symptoms (12.4% versus 7.1% for low-potency) and generalized anxiety disorder (19.1% versus 11.6%). About 29% of users develop cannabis use disorder, and daily intake, especially inhaled or high-potency forms, raises risks of coronary heart disease, heart attack, and stroke compared to non-daily use.
Dr. Michael Hsu, the lead author and a UCLA Health assistant professor in psychiatry and biobehavioral sciences, emphasized the disconnect: "While many people turn to cannabis seeking relief, our review highlights significant gaps between public perception and scientific evidence regarding its effectiveness for most medical conditions." He advocates for clinician guidance, including screening for cardiovascular and psychotic risks, checking drug interactions, and weighing harms against benefits before recommending THC products. Hsu added, "Patients deserve honest conversations about what the science does and doesn't tell us about medical cannabis."
The authors note limitations: the review is not systematic, lacks formal bias assessment, and includes observational data potentially affected by confounders. They call for more rigorous research to refine clinical advice. (DOI: 10.1001/jama.2025.19433)
