Assessing the Role of Cannabis in Managing Spasticity in Multiple Sclerosis: A Systematic Review and Meta-Analysis.

Background: Multiple sclerosis (MS) is a complex, heterogeneous disease, and its management remains challenging due to varying symptoms and patient responses to treatments. While injectable therapies like glatiramer acetate and beta-interferon are common, they have limitations such as side effects and varying efficacy. Cannabis has garnered attention as a potential alternative treatment, particularly for symptoms like spasticity and pain. Objective: This study aims to evaluate the efficacy of cannabis-based therapies for managing MS-related spasticity. Methods: Nine clinical trials involving 2544 MS patients were included, with studies conducted between 2003 and 2021 across multiple countries. Cannabinoid therapies studied included whole-plant extracts, oils, and smoked cannabis containing delta-9-tetrahydrocannabinol and/or cannabidiol. Spasticity was assessed using standardized scales, including the Ashworth scale (AS), visual analog scale, and numeric rating scale (NRS). Effect sizes were pooled using random or fixed effects models, and heterogeneity and publication bias were evaluated using I(2), Tau(2), and funnel plots. Results: The overall meta-analysis revealed a standardized mean difference (MD) of 39.19 (95% CI: 34.32-44.05) in spasticity scores, indicating notable improvement post-treatment. Subgroup analyses showed a MD of 20.36 (95% CI: 20.35-20.37) for AS and 1.18 (95% CI: 1.16-1.21) for NRS. However, substantial heterogeneity (I(2) = 100% for overall and AS analyses; 91% for NRS) and asymmetry in funnel plots suggest possible publication bias and study variability. Short-term studies demonstrated modest changes (MD = 4.53, 95% CI: -0.06 to 9.12), while long-term studies yielded larger effects (MD = 75.81, 95% CI: 66.39-85.22). Adverse events were generally mild, including dizziness and dry mouth. Conclusion: Cannabis-based therapies are associated with clinically meaningful improvements in MS-related spasticity, particularly over longer durations. Despite the promising findings, high heterogeneity and suspected bias necessitate caution. Further high-quality randomized trials with standardized protocols and comprehensive safety assessments are warranted to validate efficacy and long-term outcomes.