Association of exposure to Toxoplasma gondii, Epstein-Barr Virus, Herpes Simplex virus Type 1 and Cytomegalovirus with new-onset depressive and anxiety disorders: An 11-year follow-up study

Background: Some prevalent infections have been associated with common mental disorders, but there are few longitudinal studies, and results are inconsistent. We aimed to assess whether serological evidence of exposure to Toxoplasma gondii (T. gondii), Epstein-Barr Virus (EBV), Herpes Simplex virus Type 1 (HSV-1) and Cytomegalovirus (CMV) predict development of new-onset depressive and anxiety disorders. Methods: In a nationally representative sample of the Finnish adult population aged 30 and over (BRIF8901, n = 8028), IgG antibodies for T. gondii, EBV, HSV-1 and CMV were measured in plasma samples. The population was followed up for 11 years and new-onset depressive and anxiety disorders were diagnosed with the Composite International Diagnostic Interview. Associations were analysed controlling for sex, age, educational level, region of residence and marital status, and in separate analyses also for C-reactive protein level. Results: Seropositivity and serointensity of the four infectious agents were not associated with an increased risk of new-onset depressive or anxiety disorders. Seropositivity for CMV at baseline was associated with a lower risk of new-onset generalized anxiety disorder (adjusted OR 0.43, 95% CI 0.22–0.86 for CMV positive persons). Conclusion: The results of this large, nationally representative longitudinal study suggest that common viral infections are not significant risk factors for common mental disorders. The association of CMV with a lower risk of generalized anxiety disorder warrants further investigation.