There’s no good evidence that marijuana and cannabis-derived compounds help the nerve pain associated with chemotherapy or conditions like fibromyalgia—and side effects may mean the treatments do more harm than good.
Nerves send all kinds of pain signals to the brain, like the ones that come after a surgery or a broken bone. The pain that happens when someone is going through chemotherapy, for example, is different—the source of the pain is the nerve itself. According to a meta-analysis published Wednesday by Cochrane, cannabis might reduce this kind of neuropathic pain but not by a lot, and not by much more than a placebo.
About 20 percent of people cut their pain in half with cannabis; about 17 percent of people also had their pain reduced by half with a placebo. At the same time, nearly 10 percent of the people taking cannabis in clinical trials had to withdraw from a study