BACKGROUND: Psychiatric comorbidity is associated with lower quality of life, more fatigue, and reduced adherence to disease-modifying therapy in multiple sclerosis (MS).

OBJECTIVES: The objectives of this review are to estimate the incidence and prevalence of selected comorbid psychiatric disorders in MS and evaluate the quality of included studies.

METHODS: We searched the PubMed, PsychInfo, SCOPUS, and Web of Knowledge databases and reference lists of retrieved articles. Abstracts were screened for relevance by two independent reviewers, followed by full-text review. Data were abstracted by one reviewer, and verified by a second reviewer. Study quality was evaluated using a standardized tool. For population-based studies we assessed heterogeneity quantitatively using the I² statistic, and conducted meta-analyses.

RESULTS: We included 118 studies in this review. Among population-based studies, the prevalence of anxiety was 21.9% (95% CI: 8.76%-35.0%), while it was 14.8% for alcohol abuse, 5.83% for bipolar disorder, 23.7% (95% CI: 17.4%-30.0%) for depression, 2.5% for substance abuse, and 4.3% (95% CI: 0%-10.3%) for psychosis.

CONCLUSION: This review confirms that psychiatric comorbidity, particularly depression and anxiety, is common in MS. However, the incidence of psychiatric comorbidity remains understudied. Future comparisons across studies would be enhanced by developing a consistent approach to measuring psychiatric comorbidity, and reporting of age-, sex-, and ethnicity-specific estimates.