In March 2018 researchers from Germany published their review of the medical scientific literature to assess the effect of cannabis for chronic neuropathic pain. A total of 16 studies with 1750 participants were included in the review. The studies were 2 to 26 weeks long and 10 studies used an oromucosal spray with a plant-derived combination of tetrahydrocannabinol and cannabidiol, 2 studies a synthetic cannabinoid mimicking tetrahydrocannabinol (nabilone), 2 studies inhaled herbal cannabis and a further 2 studies a plant-derived tetrahydrocannabinol (dronabinol). 15 of the studies compared the effect of cannabis with a placebo and one study with dihydrocodeine, which is a painkiller. The quality of the studies was considered low in two studies, moderate in 12 studies and high in two studies. Nine studies were at high risk of bias for study size. Results showed that cannabis-based medicines probably increase the number of people achieving pain relief of 30% or greater when compared with placebo. However, it was noted that 17% of individuals experienced psychiatric disorders and 61% side effects involving the nervous system. However, there was no information about long-term risks in the studies analysed.
Mücke M et al. Cannabis-based medicines for chronic neuropathic pain in adults. Cochrane Database Syst Rev. 2018 Mar 7;3:CD012182