Objective: To characterize the association between infectious mononucleosis (IM), a frequent clinical manifestation of primary Epstein-Barr virus infection after childhood, and the risk for multiple sclerosis (MS).
Methods: We conducted a systematic review and meta-analysis of case-control and cohort studies of IM and MS.
Results: The combined relative risk of MS after IM from 14 studies was 2.3 (95% confidence interval, 1.7-3.0; p < 10(-8)). Potential sources of heterogeneity (ie, study design, MS definition, and latitude) barely influenced our results.
Interpretation: We conclude that Epstein-Barr virus infection manifesting as IM in adolescents and young adults is a risk factor for MS.