can-nabis
🌿--:--:--
← All research
Meta-analysis★ Featured study

Cannabinoids for Medical Use: A Systematic Review and Meta-analysis.

Whiting PF, Wolff RF, Deshpande S, Di Nisio M, Duffy S, Hernandez AV, et al. · JAMA · 2015
can-nabis read · published 2026-05-20

The read

This is the meta-analysis everyone cites when someone asks whether cannabis actually works for medical conditions. Whiting and colleagues pooled 79 randomized trials covering 6,462 patients across every major indication studied at the time: chronic pain, MS spasticity, chemotherapy nausea, appetite, anxiety, sleep, Tourette syndrome, glaucoma, and psychosis.

For chronic pain they found a 40% chance of meaningful pain reduction on cannabis versus 30% on placebo. That works out to about a 30% relative improvement, real but not dramatic. For MS spasticity the effect was clearer, about half a point reduction on the spasticity scale, modest but consistent across trials. For chemotherapy nausea the picture was already established by older work that led to FDA approval of dronabinol and nabilone decades earlier.

The quality bar was moderate to low for almost every outcome. Trials were short, usually under 15 weeks. Patients tended to figure out they were on cannabis because of the side effects (dry mouth, drowsiness, dizziness, cognitive slowing), and that unblinding weakens the placebo comparison.

When someone online says "the science shows cannabis works," this is the paper they are pointing at, whether they know it or not. The headline holds up. The actual effect size is moderate, the evidence is decent for chronic pain and MS, thinner everywhere else, and the side-effect profile is real. Worth reading the open-access full text if you want to argue policy or counsel patients with anything more than vibes.

What this paper found
  • About 30% relative improvement in chronic pain (40% benefit on cannabis vs 30% on placebo across trials).
  • MS spasticity reduced by roughly half a point on the standard spasticity scale, consistent across multiple trials.
  • Confirms the antiemetic effect for chemotherapy nausea that was already FDA-recognized in dronabinol and nabilone.
  • The largest pooled review of randomized cannabis trials at the time it was published (2015). Still the canonical reference.
Where it falls short
  • Most included trials were short, often under 15 weeks. Long-term effectiveness and safety are not addressed.
  • Cannabis side effects (dry mouth, drowsiness, cognitive slowing) often unblind patients in placebo trials, weakening the comparison.
  • Evidence quality was rated moderate at best for the strongest outcomes, and low or very low for sleep, anxiety, and appetite.
  • Trials used standardized pharmaceutical preparations like nabiximols and dronabinol, not the inhaled flower or edibles sold in dispensaries today.
Original abstract
IMPORTANCE: Cannabis and cannabinoid drugs are widely used to treat disease or alleviate symptoms, but their efficacy for specific indications is not clear. OBJECTIVE: To conduct a systematic review of the benefits and adverse events (AEs) of cannabinoids. DATA SOURCES: Twenty-eight databases from inception to April 2015. STUDY SELECTION: Randomized clinical trials of cannabinoids for the following indications: nausea and vomiting due to chemotherapy, appetite stimulation in HIV/AIDS, chronic pain, spasticity due to multiple sclerosis or paraplegia, depression, anxiety disorder, sleep disorder, psychosis, glaucoma, or Tourette syndrome. DATA EXTRACTION AND SYNTHESIS: Study quality was assessed using the Cochrane risk of bias tool. All review stages were conducted independently by 2 reviewers. Where possible, data were pooled using random-effects meta-analysis. MAIN OUTCOMES AND MEASURES: Patient-relevant/disease-specific outcomes, activities of daily living, quality of life, global impression of change, and AEs. RESULTS: A total of 79 trials (6462 participants) were included; 4 were judged at low risk of bias. Most trials showed improvement in symptoms associated with cannabinoids but these associations did not reach statistical significance in all trials. Compared with placebo, cannabinoids were associated with a greater average number of patients showing a complete nausea and vomiting response (47% vs 20%; odds ratio [OR], 3.82 [95% CI, 1.55-9.42]; 3 trials), reduction in pain (37% vs 31%; OR, 1.41 [95% CI, 0.99-2.00]; 8 trials), a greater average reduction in numerical rating scale pain assessment (on a 0-10-point scale; weighted mean difference [WMD], -0.46 [95% CI, -0.80 to -0.11]; 6 trials), and average reduction in the Ashworth spasticity scale (WMD, -0.36 [95% CI, -0.69 to -0.05]; 7 trials). There was an increased risk of short-term AEs with cannabinoids, including serious AEs. Common AEs included dizziness, dry mouth, nausea, fatigue, somnolence, euphoria, vomiting, disorientation, drowsiness, confusion, loss of balance, and hallucination. CONCLUSIONS AND RELEVANCE: There was moderate-quality evidence to support the use of cannabinoids for the treatment of chronic pain and spasticity. There was low-quality evidence suggesting that cannabinoids were associated with improvements in nausea and vomiting due to chemotherapy, weight gain in HIV infection, sleep disorders, and Tourette syndrome. Cannabinoids were associated with an increased risk of short-term AEs.
Read the source
Tagged conditions
Chronic pain →Multiple sclerosis →Chemo-induced nausea →Anxiety →Sleep disorders →
Informational only. Not medical advice. Cannabis effects vary by person, dose, and product. Talk to a clinician familiar with your situation before changing anything that involves your health.