In a study published in the Canadian Journal of Anesthesia, Meng et al attempted to evaluate patients with chronic pain seeking the use of medical cannabis. Researchers assessed the patients' demographics, patterns of cannabis use, and long-term effectiveness of cannabis on their pain and functional domains. This observational study enrolled patients between September 8, 2015, and July 31, 2018, from community-based cannabis clinics in Ontario, Canada.

To evaluate the impact of cannabis on pain intensity and pain-related interference for patients consuming cannabis for up to 12 months, data from 757 participants were investigated. Individuals with chronic disease who received medical cannabis documentation from a physician were included. In addition to demographic information, the primary outcomes studied were pain intensity and pain-related interference scores measured at baseline and 3, 6, and 12 months. Using validated questionnaires, the researchers also measured anxiety, depression, quality of life (QoL), general health symptoms, neuropathic pain, self-reported opioid consumption, and adverse events.

Meng et al found that of the 1,000 patients who consented, 757 (76%) participated at one or more of the study time points. At 6 and 12 months, 230 (30.4%) and 104 (13.7%) of participants were followed up, respectively. The majority of participants were female (62%), Caucasian (91%), and wanted cannabis for pain relief (88.9%). Time was a considerable factor correlated with improvement in pain intensity (P <.001), pain-related interference scores (P <.001), QoL (P <.001), and general health symptoms (P <.001). Among participants who reported seeking cannabis to relieve pain, 42.1% reported being on opioid therapy at baseline.

At 12 months, the percentage of individuals who reported using opioids declined by almost 50%, from 40.8% at baseline to 23.9%. The authors noted that expanded length of cannabis use was considerably correlated with improvements in pain intensity, pain-related interference, QoL, and general health symptoms (P <.001), irrespective of baseline use or reason for seeking medical cannabis.

The results of this study indicate that long-term cannabis use leads to enhancements in pain measures, QoL, and opioid use. The researchers also noted that female participants had meaningfully worse scores on pain severity, pain-related interference, anxiety, depression, QoL, and general health symptoms, but this may be explained by previous studies that found men to be more likely than females to seek cannabis for recreational purposes while females principally use cannabis for medicinal purposes.

The researchers concluded that in spite of considerable challenges to collecting long-term observational data on patients attempting a trial of cannabis products, approximately one-third of patients in the cohort stayed on medical cannabis for 6 months. They also reported that in this cohort, pain-intensity and pain-related interference scores were decreased and QoL and general health symptoms scores were enhanced compared with baseline. They added that future research with more diverse participants and greater research coordinator follow-up are warranted.

Research that seeks to comprehend why participants drop out of studies may aid in understanding whether cannabis efficiently relieves pain in a specific subset of the population.

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