Long-Term Cannabis Use Improves Pain and QoL While Decreasing Opioid Use

Photo of dry medical marijuana buds with shallow DOF
Although studies have shown cannabis reduces pain and has opioid-sparing effects, a large-scale longitudinal clinical study on the effects of cannabis products on patients was needed.

Using medical cannabis for 6 months reduces pain intensity and pain-related interference and improves quality of life, according to the results of a study published in the Canadian Journal of Anesthesia.

Although studies have shown cannabis reduces pain and has opioid-sparing effects, large-scale longitudinal clinical studies on the effects of cannabis products on patients have yet to be conducted.

To assess the impact of cannabis on pain intensity and pain-related interference for patients consuming cannabis for up to 12 months, data from 757 participants (61.6% women) were analyzed. Individuals with chronic disease who received medical cannabis documentation from a physician were included. Participants completed questionnaires regarding pain, quality of life, opioid use, and mental health at the initial visit and at 3, 6, and 12 months after baseline.

As many as 88.9% of participants sought cannabis for pain relief. Significantly more men than women were already using cannabis at baseline (45.6% vs 35.4%; P =.047), but there was no significant difference in outcomes between baseline users and those who were not using cannabis at baseline.

Among participants who reported seeking cannabis to alleviate pain, 42.1% reported being on opioid therapy at baseline. This proportion dropped to 23.9% at 12 months. Of the people who reported being on opioid therapy at baseline, 50.0% who completed the 12-month follow-up were still on opioids.

Increased duration of cannabis use was significantly associated with improvements in pain intensity, pain-related interference, quality of life, 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 improvements in pain measures, quality of life, and opioid use.

Women had significantly worse scores on pain severity, pain-related interference, anxiety, depression, quality of life, and general health symptoms, but this may be explained by previous studies that found men to be more likely than women to seek cannabis for recreational purposes whereas women primarily use cannabis for medicinal purposes.

The opioid-sparing effect with cannabis use may be due to the overlapping neuroanatomical distribution of opioid and cannabinoid receptors, as found in previous studies.

Limitations to this study include the significant attrition in the survey respondents, with only 13.7% of participants completing questionnaires at the 12-month follow-up time point. This may indicate that cannabis is helpful for only a subset of the population.

Future research with more diverse participants and greater research coordinator follow-up are warranted. Research that seeks to understand why participants drop out of studies may aid in understanding whether cannabis effectively alleviates pain in a specific subset of the population.


Meng H, Page MG, Ajrawat P, et al. Patient-reported outcomes in those consuming medical cannabis: a prospective longitudinal observational study in chronic pain patients. Published online January 20, 2021. Can J Anaesth. doi:10.1007/s12630-020-01903-1