Lack of evidence for cannabis in adults with chronic neuropathic pain

There was no high-quality evidence for the efficacy of any CBM (herbal cannabis, plant-derived tetrahydrocannabinol [THC] or dronabinol, synthetic THC [nabilone], plant-derived THC/cannabidiol [CBD] combination) in any condition with chronic neuropathic pain. The studies were 2–26 weeks in duration and compared an oromucosal spray with a plant-derived combination of THC and CBD (10 studies), a synthetic cannabinoid mimicking THC (nabilone; 2 studies), inhaled herbal cannabis (2 studies) and plant-derived THC (dronabinol; 2 studies) against placebo (15 studies) and a dihydrocodeine analgesic (1 study). Herbal cannabis was not different from placebo in reducing pain and the number of people who dropped out due to side effects. Some adverse events (particularly somnolence or sedation, confusion, psychosis) might limit the clinical usefulness of cannabis-based medicines.