Cannabis use, pain and prescription opioid use in people living with chronic non-cancer pain : Findings from a four-year prospective cohort

Gabrielle Campbell, Wayne D. Hall, Amy Peacock, Nicholas Lintzeris, Raimondo Bruno, Briony Larance, Suzanne Nielsen, Milton Cohen, Gary Chan, Richard P. Mattick, Fiona Blyth, Marian Shanahan, Timothy Dobbins, Michael Farrell, Louisa Degenhardt

Lancet Public Health, 2018, 3, (7): e341–e350.

doi:10.1016/S2468-2667(18)30110-5.

 

Abstract

Background : There has been growing interest in the use of cannabis and cannabinoids to treat chronic non-cancer pain (CNCP). Cannabis and cannabinoids have attracted attention because of their greater safety compared with opioids, and the possibility that their use can reduce opioid dose requirements via an opioid-sparing effect. Both factors have been proposed to contribute to fewer opioid-related deaths.
Methods: We used The Pain and Opioids IN Treatment (POINT) study, a national cohort of 1,514 people living with CNCP prescribed opioids, to examine relationships between cannabis use, opioid use and pain outcomes over four years.

Outcomes : Cannabis use was common, and by four-year follow-up, 24.3% had used cannabis for pain. Interest in using cannabis for pain doubled from 33% (baseline) to 60% (four years). We found that patients who had used cannabis had greater pain severity and interference, lower pain self-efficacy, and greater GAD severity than patients who had not used cannabis. We found no evidence of a temporal relationship between cannabis use and pain severity or pain interference, and no evidence that cannabis use reduced prescribed opioid use or increased rates of opioid discontinuation.

Interpretation : Cannabis use was common in people living with CNCP prescribed opioids, but we found no evidence that cannabis use improved patient outcomes. Those who used cannabis had greater pain and lower self-efficacy in managing pain and there was no evidence that cannabis use reduced pain severity or interference or exerted an opioid-sparing effect.

 

Introduction

The use of prescribed opioids in the treatment of chronic non-cancer pain (CNCP) is controversial, due to a lack of evidence of their long-term effectiveness1,2 and increased opioid harms in countries as opioid prescribing for CNCP has increased3,4.

Alternatives to opioids are increasingly being debated and considered. Recent reviews of cannabinoids suggest they may have some efficacy in some CNCP conditions5–7. In Australia8, the United States (U.S.)9, Canada10 and the Netherlands11, CNCP is the most commonly cited reason for using cannabis for medicinal purposes. There has also been increasing discussion about the potential opioid-sparing effects of cannabinoids12. Changes in regulations mean that it is likely that there will be an increase in use of cannabinoid products for CNCP.

Longitudinal studies of cannabis use among people with CNCP are limited. Randomised controlled studies typically exclude those with complex physical, substance use and mental health comorbidities, which comprises a substantial number of people living with CNCP16. There is limited evidence on efficacy in the most common CNCP conditions, namely back or neck problems, arthritis and migraine7,13There is a lack of long-term follow-up in prospective studies, with the majority being 12-months or less17–19. Discussion about the opioid-sparing effects of cannabinoids has often been confined to ecological studies or cross-sectional surveys, which are poorly suited for testing causal hypotheses.

We used The Pain and Opioids IN Treatment (POINT) study, a national cohort of people living with CNCP prescribed opioids, to examine cannabis use and pain outcomes over four years. We aimed to examine :

1. Cannabis use over four years in people living with CNCP and who had been prescribed opioids, including their reasons for use and perceived effectiveness of cannabis;

2. Associations between level of cannabis use in the past month and pain, mental health and opioid-use;

3. The impact of cannabis use on pain severity and interference over time, while controlling for potential confounding of demographic and clinical variables;

4. Potential opioid-sparing effects of cannabis, controlling for potential confounding variables.

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