UK Medical Cannabis Registry: A Clinical Outcomes Analysis for Complex Regional Pain Syndrome

Complex regional pain syndrome is characterized by severe, persistent pain. Emerging evidence suggests that cannabis-based medicinal products may represent a new therapeutic option. However, to date, no clinical studies have evaluated the effects of cannabis-based medicinal products in individuals with complex regional pain syndrome. The aim of this study is to assess changes in patient-reported outcome measures and the prevalence of adverse events associated with cannabis-based medicinal products prescribed for complex regional pain syndrome.

This case series assessed changes in patient-reported outcome measures over 6 months in complex regional pain syndrome patients enrolled in the UK Medical Cannabis Registry. Adverse events were measured and graded using the Common Terminology Criteria for Adverse Events version 4.0.

A total of 64 patients were identified for inclusion. At baseline, pain severity measured by the Brief Pain Inventory Short Form was 6.69 ± 1.42. This improved at 1 (5.85 ± 1.73), 3 (5.91 ± 1.82), and 6 months (6.05 ± 1.72; p < 0.050). Participants also reported improvements in severity as measured by the Short Form-McGill Pain Questionnaire-2 and pain visual analogue scale at the same time points (p < 0.050). Participants also reported improvements in anxiety symptoms, sleep quality, and general health-related quality of life (p < 0.050), as measured by validated measures. Five patients (7.81%) reported 50 (78.13%) adverse events.

This study represents the outcomes in individuals with complex regional pain syndrome prescribed cannabis-based medicinal products. These suggest initiation of cannabis-based medicinal products is associated with improvements in patient-reported outcome measures. While these findings are consistent with the literature, they must be interpreted with caution, considering the limitations of this study.

Cannabis-based medicinal products were associated with improvements in pain severity and interference. Participants also reported improvements in important metrics of health-related quality of life. This supports further research through high-quality randomized controlled trials to ascertain the efficacy of cannabis-based medicinal products in improving complex regional pain syndrome symptoms.