UK Medical Cannabis Registry: A Two‐Year Prospective Observational Cohort Study of Clinical Outcomes in Insomnia

BACKGROUND: Insomnia disorder affects approximately 10% of people. The persistence of insomnia, despite treatment, remains high. Cannabis-based medicinal products (CBMPs) have been proposed as a potential treatment for insomnia. This study aims to use data from the UK Medical Cannabis Registry to analyze changes in self-reported sleep quality in patients prescribed CBMPs for insomnia. METHODS: A prospective cohort study of patients treated with CBMPs for insomnia was completed. The primary outcome was the Single-Item Sleep Quality Scale (SQS). This was assessed at baseline and at 1, 3, 6, 12, 18, and 24 months from baseline. Secondary outcomes included change in anxiety and general health-related quality of life. p-values < 0.050 were considered statistically significant. RESULTS: Two hundred and eleven participants met the inclusion criteria. Over half (n = 126; 59.72%) were users of cannabis at baseline. At the primary endpoint of 24 months, mean SQS improved from 2.46 ± 2.10 (mean ± standard deviation (SD)) at baseline to 5.14 ± 2.75 (mean difference +2.68; 95% confidence interval (CI) 2.23-3.14; p < 0.001), with improvements observed at all timepoints. SQS values of 0 (odds ratio (OR) 15.49; 95% CI 3.87-65.19; p < 0.001) and 1-3 (OR 4.90; 95% CI 1.87-13.80; p = 0.002) at baseline and prescription of dried flower CBMPs (OR 4.99; 95% CI 1.27-21.39; p = 0.025) were associated with clinically significant improvements in sleep quality at 24 months. Seventeen participants (8.06%) reported adverse events. Participants aged over 60 were more likely to report an adverse event (OR 19.08; 95% CI 1.52-535.75; p = 0.036). CONCLUSION: Initiation of CBMPs was associated with improvements in self-reported sleep quality across 2 years, with the largest associations observed in those with the most severe impairment. As an uncontrolled, observational study of a self-selected and predominantly cannabis-experienced cohort, placebo effects, regression to the mean, and selection bias cannot be excluded.