A research team led by Dr. Mark Ware of the Research Institute of the McGill University Health Centre (RI-MUHC) in Montréal, Canada, recently completed a national multi-center study on the safety of medical-cannabis use among patients with chronic pain.
The study revealed that patients who used cannabis daily for a year (and were closely monitored) saw no increase in serious adverse events compared with pain patients who did not use cannabis.
The results of the study were published online in the Journal of Pain.
"This is the first and largest study of long-term safety of medical-cannabis use by patients suffering from chronic pain ever conducted," Ware, a pain specialist at the Montreal General Hospital of the RI-MUHC and associate professor in Family Medicine and Anesthesia at McGill University. "We found that medical cannabis, when used by patients who are experienced users and as part of a monitored treatment program for chronic pain over one year, appears to have a reasonable safety profile."
The study, titled "Cannabis for the Management of Pain: Assessment of Safety Study" (COMPASS), followed 215 adult patients with chronic noncancer pain and was launched in 2004.
Seven pain-management centers from across Canada participated in the study. Cannabis for the study was obtained from a licensed cannabis producer and contained 12.5 percent THC. Subjects received lung-function and cognitive testing; their pain, mood and quality of life were evaluated in one year of follow-up.
"Our data show that daily cannabis users had no greater risk than non-users (control group) to experience serious adverse events,'' Ware said. ''We found no evidence of harmful effects on cognitive function, or blood tests among cannabis consumers, and we observed a significant improvement in their levels of pain, symptom distress, mood and quality of life compared to controls."
Researchers did report an increased risk of nonserious adverse events in medical-cannabis consumers such as headache, nausea, dizziness, somnolence and respiratory problems associated with smoking.
