Psychiatric comorbidity is associated with disability progression in multiple sclerosis.

Objective: Emerging evidence suggests that comorbidity may influence disability outcomes in multiple sclerosis (MS); we investigated the association between psychiatric comorbidity and MS disability progression in a large multiclinic population.

Methods: This retrospective cohort study accessed prospectively collected information from linked clinical and population-based health administrative databases in the Canadian provinces of British Columbia and Nova Scotia. Persons with MS who had depression, anxiety, or bipolar disorder were identified using validated algorithms using physician and hospital visits. Multivariable linear regression models fitted using an identity link with generalized estimating equations were used to determine the association between psychiatric comorbidity and disability using all available Expanded Disability Status Scale (EDSS) scores.

Results: A total of 2,312 incident cases of adult-onset MS were followed for a mean of 10.5 years, during which time 35.8% met criteria for a mood or anxiety disorder. The presence of a mood or anxiety disorder was associated with a higher EDSS score (β coefficient = 0.28, = 0.0002, adjusted for disease duration and course, age, sex, socioeconomic status, physical comorbidity count, and disease-modifying therapy exposure). Findings were statistically significant among women (β coefficient = 0.31, = 0.0004), but not men (β coefficient 0.22, = 0.17).

Conclusion: Presence of psychiatric comorbidities, which were common in our incident MS cohort, increased the severity of subsequent neurologic disability. Optimizing management of psychiatric comorbidities should be explored as a means of potentially mitigating disability progression in MS.