Values and preferences towards medical cannabis among people living with chronic pain: a mixed-methods systematic review.

Objective: To explore values and preferences towards medical cannabis among people living with chronic pain.

Design: Mixed-methods systematic review.

Data Sources: We searched MEDLINE, EMBASE and PsycINFO from inception to 17 March 2020.

Study Selection: Pairs of reviewers independently screened search results and included quantitative, qualitative and mixed-methods studies reporting values and preferences towards medical cannabis among people living with chronic pain.

Review Methods: We analysed data using meta-narrative synthesis (quantitative findings were qualitised) and tabulated review findings according to identified themes. We used the Grading of Recommendations Assessment, Development and Evaluation approach to assess certainty of evidence.

Results: Of 1838 initial records, 15 studies proved eligible for review. High to moderate certainty evidence showed that patient's use of medical cannabis for chronic pain was influenced by both positive (eg, support from friends and family) and negative social factors (eg, stigma surrounding cannabis use). Most patients using medical cannabis favoured products with balanced ratios of tetrahydrocannabinol (THC) and cannabidiol (CBD), or high levels of CBD, but not high THC preparations. Many valued the effectiveness of medical cannabis for symptom management even when experiencing adverse events related to concentration, memory or fatigue. Reducing use of prescription medication was a motivating factor for use of medical cannabis, and concerns regarding addiction, losing control or acting strangely were disincentives. Out-of-pocket costs were a barrier, whereas legalisation of medical cannabis improved access and incentivised use.Low to very low certainty evidence suggested highly variable values towards medical cannabis among people living with chronic pain. Individuals with pain related to life-limiting disease were more willing to use medical cannabis, and preferred oral over inhaled administration.

Conclusions: Our findings highlight factors that clinicians should consider when discussing medical cannabis. The variability of patients' values and preferences emphasise the need for shared decision making when considering medical cannabis for chronic pain.