Taking medical cannabis for 6 months reduces pain intensity and pain-related disorders and improves quality of life. This emerges from the results of a study published in the Canadian Journal of Anesthesia.

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

To evaluate the impact of cannabis on pain intensity and pain-related disorders in patients who use cannabis for up to 12 months, data from 757 participants (61.6% women) were analyzed. People with chronic diseases who had received medical cannabis documentation from a doctor were included. Participants completed questionnaires on pain, quality of life, opioid use, and mental health at the first visit and 3, 6, and 12 months after the start of the study.

88.9% of the participants looked for cannabis for pain relief. Significantly more men than women already used cannabis at the start of the study (45.6% versus 35.4%; P = 0.047), but there was no significant difference in the results between the users at the start of the study and those who did not use cannabis at the start of the study.

42.1% of participants who said they were looking for cannabis for pain relief said they had received opioid therapy at baseline. This proportion fell to 23.9% after 12 months. Of those who reported receiving 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 disorders, quality of life, and general health symptoms (P <0.001), regardless of basic use or the reason for seeking medical cannabis.

The results of this study show that long-term cannabis use leads to improvements in pain control measures, quality of life, and opioid use.

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

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

One of the limitations of this study is the significant wear and tear in the respondents. Only 13.7% of the participants completed questionnaires at the 12-month follow-up time. This may indicate that cannabis is only helpful for part of the population.

Future research with more diverse participants and better follow-up of research coordinators is needed. Research aimed at understanding why participants drop out can help understand whether cannabis is effective at relieving pain in a particular subset of the population.


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