Cannabis and cannabinoids for the treatment of people with chronic non-cancer pain conditions: a systematic review and meta-analysis of controlled and observational studies.

This review examines evidence cannabinoids in chronic non-cancer 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 RCTs and 57 observational studies. Forty-eight studies examined neuropathic pain, seven studies examined fibromyalgia, one rheumatoid arthritis, and 48 other CNCP (13 MS-related pain, 6 visceral pain, and 29 samples with mixed or undefined CNCP). Across RCTs, PERs for 30% reduction in pain were 29.0% (cannabinoids) vs 25.9% (placebo), significant effect for cannabinoids, number needed to treat to benefit (NNTB): 24 (95%CI 15-61); for 50% reduction in pain, PERs were 18.2% vs. 14.4%; no significant difference. Pooled change in pain intensity (standardised mean difference: -0.14, 95%CI -0.20, -0.08) was equivalent to 3mm on a 100mm visual analogue scale greater than placebo. In RCTs, PERs for all-cause AEs were 81.2% vs. 66.2%; number needed to treat to harm (NNTH): 6 (95%CI 5-8). There were no significant impacts upon 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 NNTB are high, and NNTH low, with limited impact on other domains. It appears unlikely that cannabinoids are highly effective medicines for CNCP.