Medical Marijuana for Pain: What the Evidence Shows

Twenty-eight studies were undertaken to evaluate the effectiveness of cannabinoids for chronic pain. Of these, only 2 were found to be at low risk of bias. 

Overall, these studies seem to indicate that cannabinoids have a significant role to play in the management of chronic pain. However, there are important issues that limit the validity of this conclusion. First and most important is how the improvement in pain was evaluated. In many of the studies, only instruments to measure the level of pain, most notably the Visual Analogue Scale, were used. This is fine when one is measuring acute pain. But when it comes to chronic pain—which is what the studies were looking at—the most important measures of the impact of any treatment are improvement in functioning and other objective measures, such as reduction in use of analgesic medications.