This review examines evidence for the effectiveness of cannabinoids in chronic noncancer pain (CNCP) and addresses gaps in the literature by: considering differences in outcomes based on cannabinoid type and specific CNCP condition; including all study designs; and following IMMPACT guidelines. MEDLINE, Embase, PsycINFO, CENTRAL, and clinicaltrials.gov were searched in July 2017. Analyses were conducted using Revman 5.3 and Stata 15.0. A total of 91 publications containing 104 studies were eligible (n = 9958 participants), including 47 randomised controlled trials (RCTs) and 57 observational studies. Forty-eight studies examined neuropathic pain, 7 studies examined fibromyalgia, 1 rheumatoid arthritis, and 48 other CNCP (13 multiple sclerosis–related pain, 6 visceral pain, and 29 samples with mixed or undefined CNCP). Across RCTs, pooled event rates (PERs) for 30% reduction in pain were 29.0% (cannabinoids) vs 25.9% (placebo); significant effect for cannabinoids was found; number needed to treat to benefit was 24 (95% confidence interval [CI] 15-61); for 50% reduction in pain, PERs were 18.2% vs 14.4%; no significant difference was observed. Pooled change in pain intensity (standardised mean difference: −0.14, 95% CI −0.20 to −0.08) was equivalent to a 3 mm reduction on a 100 mm visual analogue scale greater than placebo groups. In RCTs, PERs for all-cause adverse events were 81.2% vs 66.2%; number needed to treat to harm: 6 (95% CI 5-8). There were no significant impacts on physical or emotional functioning, and low-quality evidence of improved sleep and patient global impression of change. Evidence for effectiveness of cannabinoids in CNCP is limited. Effects suggest that number needed to treat to benefit is high, and number needed to treat to harm is low, with limited impact on other domains. It seems unlikely that cannabinoids are highly effective medicines for CNCP.
aNational Drug and Alcohol Research Centre, Faculty of Medicine, UNSW Sydney, Sydney, New South Wales, Australia
bCentre for Youth Substance Abuse Research, University of Queensland, Brisbane, Queensland, Australia
cNational Addiction Centre, Institute of Psychiatry, Psychology & Neuroscience, Kings College London, London, United Kingdom
dDiscipline of Addiction Medicine, Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
eDrug Health Services, Concord Repatriation General Hospital, Sydney Local Health District, NSW Health, Sydney, New South Wales, Australia
Corresponding author. Address: 22-32 King St, Randwick 2031, New South Wales, Australia. Tel.: +61(2) 9385 0162; fax: +61 (2) 9385 0222. E-mail address: email@example.com (E. Stockings).
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Received December 07, 2017
Received in revised form April 22, 2018
Accepted May 01, 2018