Pain Severity Trajectories and Patient Profiles in Chronic Pain Patients Treated with Cannabis-Based Medicinal Products: A k-Means Clustering Analysis of the UK Medical Cannabis Registry.

Erridge S.; Datta A.; Mukherjee A.; Vasooja D.; Coomber R.; Beri S.; Khan S.; Weatherall M.; Platt M.; Rucker J. et al. · Journal of clinical pharmacology · 2026

**Background & Methods** This cohort study analyzed data from 3,744 UK Medical Cannabis Registry participants with chronic pain as their primary indication, using longitudinal k-means clustering to identify distinct pain-severity trajectory patterns over 24 months. Patient-reported outcome measures including the Brief Pain Inventory Short Form (BPI-SF), EuroQol 5-Dimension 5-Level (EQ-5D-5L), Generalised Anxiety Disorder-7, and Single-Item Sleep Quality Scale were assessed at baseline through 24 months, with logistic regression used to identify baseline predictors of cluster membership. **Key Findings** • All measured outcomes improved significantly from baseline to 24 months: pain severity (effect size d = 0.57), pain interference (d = 0.59), and health-related quality of life EQ-5D-5L index (d = -0.76), with more than half of patients achieving minimal clinically important differences in pain measures (all P < 0.001). • Five distinct pain-severity trajectory clusters emerged with varying patterns and magnitudes of improvement, though all clusters demonstrated reduction below baseline severity levels, indicating heterogeneous treatment response among the patient population. • Baseline sleep quality, anxiety levels, and treatment indication were stronger predictors of clinical response than cannabis product type or dosing factors, suggesting patient characteristics rather than pharmaceutical variables drive treatment outcomes. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Adverse events were reported by 14.37% (n = 538) of patients, with the majority classified as mild or moderate in severity. Specific adverse event types were not detailed in the abstract. **Evidence Quality** This study represents real-world observational data from a clinical registry rather than a randomized controlled trial, limiting causal inference. The large cohort size and longitudinal follow-up through 24 months provide substantial descriptive evidence for treatment response patterns in UK chronic pain patients. Key limitations include lack of control group comparison, potential selection bias inherent in registry populations, and reliance on patient-reported outcomes. The clustering methodology effectively identifies response phenotypes but requires external validation. This evidence supports CBMP use in clinical practice settings but does not establish superiority over standard analgesics.

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