Published in the Canadian Journal of Anaesthesia in May 2021, this was a 12 month observational study that followed patients suffering from chronic pain and who were enrolled in the medical cannabis program in Canada.
"...pain intensity and pain-related interference scores were reduced and QoL [Quality of Life] and general health symptoms scores were improved compared with baseline."
An interesting aspect of this study was that the improvements in pain metrics increased over time, which infers that cannabis medicine for pain probably works best when consistently used over many months. Initially, about 41% reported using opioids to manage their pain, and after 12 months, only 24% were still using opioids to help manage their pain.
The abstract of the study is here.