Objectives: The objective of this prospective, open-label study was to determine the long-term effect of medicinal cannabis treatment on pain and functional outcomes in participants with treatment-resistant chronic pain.
Patients and methods: The primary outcome was the change in the pain symptom score on the S-TOPS (Treatment Outcomes in Pain Survey-Short Form) questionnaire at the 6-month follow-up in an intent-to-treat population. Secondary outcomes included the change in S-TOPS physical, social, and emotional disability scales, the pain severity, and pain interference on the Brief Pain Inventory, sleep problems, and the change in opioid consumption.
Results: A total of 274 participants were approved for treatment; complete baseline data were available for 206 (intent-to-treat), and complete follow-up data for 176 participants. At follow-up, the pain symptom score improved from median 83.3 (95% confidence interval [CI], 79.2-87.5) to 75.0 (95% CI, 70.8-79.2) (P<0.001). The pain severity score (7.50 [95% CI, 6.75-7.75] to 6.25 [95% CI, 5.75-6.75]) and the pain interference score (8.14 [95% CI, 7.28-8.43] to 6.71 [95% CI, 6.14-7.14]) improved (both P<0.001), together with most social and emotional disability scores. Opioid consumption at follow-up decreased by 44% (P<0.001). Serious adverse effects led to treatment discontinuation in 2 participants.
Discussion: The treatment of chronic pain with medicinal cannabis in this open-label, prospective cohort resulted in improved pain and functional outcomes, and a significant reduction in opioid use. Results suggest long-term benefit of cannabis treatment in this group of patients, but the study's noncontrolled nature should be considered when extrapolating the results.