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Abstract
Reviews of the effectiveness of medicinal cannabis for chronic pain vary in their conclusions. IASP has identified that a key missing evidence in this debate is data from observational cohort studies, analyzed with comparative effectiveness methods. In a medically supervised context to the use of marijuana for chronic pain, we identified 440 patients certified for medical marijuana by pain specialists in a single healthcare system. They were characterized by a battery of patient-reported outcomes stored electronically in the University of Pittsburgh Patient Outcomes Repository for Treatment (PORT). At 3 months, 38.6% were responders, based on clinically meaningful improvements in pain, function, or global impression of change, and maintained this response at 6 months. In the 157 patients who were coprescribed opioids, at 6 months there was a mean 39.3% decrease in morphine milligram equivalents (P < 0.05 for the difference vs baseline). In addition, 8114 patients treated in the same pain clinics with prescription pain medications instead (nonopioid or opioid) during the same timeframe were selected from PORT as a control group for comparison. They had a 34.9% rate of response at 3 months. Using the causal inference method of stratified modeling, logistic regression revealed an odds ratio of 2.6 in favor of medical marijuana vs medication treatment (P < 0.01). Potential harms data were not available in the PORT registry. Medical marijuana was comparatively more effective than prescription medications for the treatment of chronic pain at 3 months, although the populations compared were slightly different.
