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

Koye A.; Erridge S.; Clarke E.; McLachlan K.; Coomber R.; Rucker J.; Weatherall M.; Sodergren M. · Neuropsychopharmacology reports · 2026

**Background & Methods** This was a two-year prospective cohort study utilizing data from the UK Medical Cannabis Registry examining 211 patients prescribed cannabis-based medicinal products (CBMPs) for insomnia disorder. Sleep quality was assessed at baseline and multiple timepoints (1, 3, 6, 12, 18, and 24 months) using the Single-Item Sleep Quality Scale (SQS), with secondary outcomes including anxiety and quality of life measures. **Key Findings** - At 24 months, mean SQS scores improved significantly from 2.46 at baseline to 5.14 (p <0.001), representing a clinically meaningful improvement of 2.68 points across all measured timepoints. - Patients with the most severe baseline impairment—those with SQS scores of 0 (OR 15.49) or 1-3 (OR 4.90)—demonstrated the largest treatment-associated improvements in sleep quality. - Dried flower CBMP formulation was associated with clinically significant improvements (OR 4.99; p=0.025), and 59.72% of participants were cannabis-experienced users at baseline. **Dosage & Administration** Not reported. The study does not specify doses, cannabinoid ratios (THC:CBD), or detailed administration protocols beyond identifying dried flower as an effective formulation. **Safety & Adverse Effects** Adverse events occurred in 17 participants (8.06%). Age >60 years was a significant risk factor for adverse event reporting (OR 19.08; 95% CI 1.52-535.75; p=0.036). Specific adverse event types were not detailed in the available abstract. **Evidence Quality** This study represents low-to-moderate quality evidence with significant limitations. As an uncontrolled, observational cohort study, it cannot establish causation due to unmeasured confounders, selection bias from a self-selected predominantly cannabis-experienced population, placebo effects, and regression to the mean. The lack of control group, reliance on self-reported outcomes, and potential monitoring/attention effects further limit interpretation. The small sample size (n=211) and high baseline cannabis use prevalence limit generalizability to treatment-naïve populations. While the consistent improvements across 24 months and association with baseline severity suggest possible benefit, these findings require validation through randomized controlled trials before clinical recommendations can be established.

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