Decades of research, one honest scorecard. We lead with the strongest findings and label every one, because strong evidence speaks for itself.
Our labels are based on the evidence categories in the landmark 2017 National Academies of Sciences report10.
Conclusive or substantial evidence: multiple good randomized trials or an official approval.
Moderate evidence: good studies with some uncertainty. Promising and supported.
Smaller human studies, or lab and animal research pointing toward new uses.
The National Academies found conclusive or substantial evidence that cannabis is an effective treatment for chronic pain in adults11. A JAMA meta-analysis of 79 trials found cannabinoids were associated with greater pain reduction than placebo20.
Oral cannabinoids are effective anti-nausea medicines for chemotherapy patients (conclusive/substantial evidence)11. In the JAMA meta-analysis, 47% of patients on cannabinoids had a complete nausea and vomiting response, compared with 20% on placebo20. Two THC-based medicines, Marinol and Syndros (dronabinol), plus Cesamet (nabilone), are FDA-approved for it21.
Oral cannabinoids improve patient-reported MS spasticity symptoms (conclusive/substantial evidence)11, and trials show reduced spasticity scores versus placebo20.
The FDA approved Epidiolex, a purified cannabis-derived CBD medicine, for seizures in Lennox-Gastaut and Dravet syndromes in patients 2 and older21. A randomized trial in the New England Journal of Medicine found it reduced convulsive seizures in children with drug-resistant Dravet syndrome22.
Dronabinol, a THC medicine, is FDA-approved to treat anorexia associated with weight loss in AIDS patients21. The National Academies also found limited evidence that cannabis increases appetite and reduces weight loss in HIV/AIDS11.
After an eight-factor review, HHS and FDA concluded marijuana has a currently accepted medical use in treatment in the United States, and recommended Schedule III54 55.
The National Academies found moderate evidence that cannabinoids improve short-term sleep in people with sleep disturbance linked to sleep apnea, fibromyalgia, chronic pain, and MS11.
In a year-long prospective study, people with PTSD who used dispensary cannabis saw bigger drops in symptoms. They were 2.57 times more likely to no longer meet PTSD criteria by the end than non-users44. A systematic review found cannabinoids may help with PTSD anxiety, memory processing, and sleep45. Researchers are now calling for larger randomized trials.
CBD improved anxiety in people with social anxiety disorder during a public-speaking test11. Researchers see this as an early, encouraging signal.
In a placebo-controlled trial, 10 of 11 patients with active Crohn's given THC-rich cannabis had a clinical response, versus 4 of 10 on placebo. Three patients came off steroid dependence, and patients reported better appetite and sleep43.
The National Academies reported limited evidence that THC capsules improve Tourette symptoms11.
The National Academies found limited evidence linking cannabinoids to better outcomes, including survival, after traumatic brain injury or brain bleeding11.
Lab research is where tomorrow's medicines start, and cannabinoids look exciting.
Researchers at the National Institute of Mental Health found that both CBD and THC protected neurons from glutamate toxicity and act as antioxidants48.
U.S. Patent 6,630,507, assigned to HHS, covers cannabinoids as antioxidants and neuroprotectants, with possible use in stroke, trauma, Alzheimer's, and Parkinson's49.
THCA showed potent neuroprotective activity in a mouse model of Huntington's disease, improving motor deficits and reducing brain inflammation46.
Some of the most hopeful research is about what people stop using once they have cannabis.
Heavy drinkers in treatment drank about 29% fewer drinks and were about half as likely to binge on days they used cannabis15. Among Canadian medical-cannabis patients, 44% reported drinking less often after starting cannabis and 8% stopped drinking entirely14. In a California survey, 40% used cannabis as a substitute for alcohol13.
In Medicare Part D, states with medical cannabis dispensaries saw about 3.74 million fewer daily opioid doses filled per year in the average state50. In one patient survey, 30% reported substituting cannabis for opioids51. In another, patients reported completely stopping 59% of the opioid medications they had substituted52.
THCA is non-intoxicating, and lab studies point to anti-inflammatory, immune-modulating, and neuroprotective properties19. In animal studies, THCA strongly reduced nausea and vomiting at doses where THC didn't47.
THC vs. THCA, explained →Reefer Sanity is an education site about adult cannabis use.