http://www.cannabis-med.org/english/bulletin/ww_en_db_cannabis_artikel.php?id=461The use of herbal cannabis was associated with a higher rate of minor or moderate adverse events compared to non-using controls, but there was no difference in serious side effects at an average dose of 2.5g cannabis per day. This is a result of the COMPASS study (Cannabis for the Management of Pain: Assessment of Safety Study). This national multicentre study looked at the safety of medical cannabis use among patients suffering from chronic pain and was led by Dr Mark Ware of the McGill University Health Centre in Montréal, Canada. The scientists found that patients with chronic pain, who used cannabis daily for one year, when carefully monitored, did not have an increase in serious adverse events compared to pain patients who did not use cannabis. The researchers followed 215 adult patients, with chronic non-cancer pain, who used medical cannabis, and compared them to a control group of 216 chronic pain sufferers who were not cannabis users. The study involved seven pain centres across Canada. The cannabis users were given access to herbal cannabis containing 12.5% THC from a licensed cannabis producer. Every month patients were asked to give information on adverse effects and underwent lung function and cognitive testing, and were asked about their pain, mood and quality of life. Ware MA, Wang T, Shapiro S, Collet JP; COMPASS study team. Cannabis for the Management of Pain: Assessment of Safety Study (COMPASS). J Pain. 2015 Sep 15. [in press] Science Daily of 29 September 2015