Prevalence and Odds of Bipolar Disorder in Patients with Multiple Sclerosis (MS): a Systematic Review and Meta-Analysis.

Background: Patients with multiple sclerosis (MS) suffer from a wide range of physical and psychiatric disorders. The literature shows an increased prevalence of bipolar disorder (BD) in MS patients. Objective: To estimate the pooled prevalence and odds of BD in patients with MS. Methods: PubMed, Scopus, EMBASE, Web of Science, PsycINFO and Google Scholar were systematically searched by two independent reviewers on March 1, 2024. Results: A literature search revealed 2228 records, of which 107 full texts were evaluated and finally, 34 studies remained for systematic review. The prevalence of BD in included studies ranged between 1% and 20%, and the estimated pooled prevalence was 3% (95% CI 2-4%) (I2=99%, p<0.001). The pooled prevalence of BD in patients with MS was estimated as 3% (95% CI 1-5%) in America and Europe continents (3%, 95% CI: 1-8%), and 2% (95% CI 1-3%) in Asia. The odds ratio (OR) of BD in MS cases ranged between 2.17 and 17.9, and the estimated pooled OR was 3.84 (95% CI 1.75-8.41) (I2=93%, P<0.01). Conclusions: The findings of this systematic review indicate that BD is relatively common among MS patients, who have an approximately threefold higher risk of developing BD than the general population. Subgroup analysis showed that the pooled prevalence of BD was lowest in Asia compared with Europe and the Americas.