Recently, a team of Canadian doctors and researchers led by Dr. Mark Ware from McGill University worked with seven clinics across Canada to evaluate the long-term safety and efficacy of using cannabis to treat chronic pain. Their results, newly published in the Journal of Pain, lend support to the use of cannabis to manage chronic pain within a monitored treatment program.
The study followed 431 adults with chronic non-cancer pain over the course of a year. Half of them were assigned to a cannabis treatment group while the other half were assigned to a control group. In all subjects, the pain had been present for at least six months, was rated moderate to severe, and other attempts at treatment had been ineffective.
The cannabis group was provided with medicinal cannabis from Canadian provider Prairie Plant Systems (the parent company of CanniMed) which contained 12.5% THC. Subjects used a median of 2.5 grams per day and were allowed to use the delivery system of their choosing. 27% chose to only smoke and 8% only consumed cannabis orally, while 61% preferred a combination of smoking, vaporization, and oral ingestion.
Use of medical cannabis to treat chronic pain did not increase the risk of serious adverse events, but it was associated with an increase in the risk of non-serious adverse events, the most common of which were headaches, nausea, drowsiness, and dizziness. Experienced cannabis users had a lower incidence of adverse events. The cannabis group also had a higher rate of non-serious respiratory conditions, which is consistent with other research associating long-term cannabis smoking with a higher risk of developing bronchitis.
Concerning the efficacy of cannabis for pain management, the cannabis group showed significant improvements in pain intensity and quality of life, as well as improvements in symptom distress and mood disturbances related to their pain.
In summary, the results point to the safety and efficacy of up to 2.5 grams per day of 12.5% THC cannabis being used by current cannabis users as part of a carefully monitored chronic pain management program when other treatments have not been successful.
This study signifies a major step forward for medicinal cannabis research, as it is the first cohort study of the long-term safety of medical cannabis use ever conducted. In Canada, the Marihuana for Medical Purposes Regulations (MMPR) require the signature of a health professional in order for a medical document to be granted, but some physicians have previously hesitated to do so due to a lack of research on long-term effects.
While the results support the safety and efficacy of medical cannabis for managing chronic pain, authors note that the cannabis group was composed of a majority of current cannabis users and that non-serious adverse events would have likely been higher if more inexperienced users were included. In light of this, they suggest that future research focus on characterizing safety issues specific to new users, and that studies with extended observation periods be conducted.
Full study available here: http://www.jpain.org/article/S1526-5900(15)00837-8/pdf