Patient-reported outcomes in those consuming medical cannabis: a prospective longitudinal observational study in chronic pain patients

Purpose We investigated patients with chronic pain seeking medical cannabis. We assessed their demographics, patterns of cannabis use, and the long-term effectiveness of cannabis on their pain and functional domains. Methods This observational study enrolled patients between 8 September 2015 and 31 July 2018 from community-based cannabis clinics in Ontario, Canada. In addition to collecting demographic information, the primary outcomes studied were pain intensity and pain-related interference scores assessed at baseline, three, six, and 12 months. Using validated questionnaires, we also assessed anxiety, depression, quality of life (QoL), general health symptoms, neuropathic pain, self-reported opioid consumption, and adverse events. Results Of the 1,000 patients consented, 757 (76%) participated at one or more of the study time points. At six and 12 months, 230 (30.4%) and 104 (13.7%) of participants were followed up, respectively. Most participants were female (62%), Caucasian (91%), and sought cannabis for pain relief (88%). Time was a significant factor associated with improvement in pain intensity (P < 0.001), pain-related interference scores (P < 0.001), QoL (P < 0.001), and general health symptoms (P < 0.001). Female sex was significantly associated with worse outcomes than male sex including pain intensity (P < 0.001) and pain-related interference (P < 0.001). The proportion of individuals who reported using opioids decreased by half, from 40.8% at baseline to 23.9% at 12 months. Conclusion Despite significant challenges to collecting long-term observational data on patients who attempted a trial of cannabis products, approximately one-third of patients in the cohort remained on medical cannabis for six months. In this cohort, pain intensity and pain-related interference scores were reduced and QoL and general health symptoms scores were improved compared with baseline.