Köhler-Forsberg O, et al. – In this nationwide study in Denmark, researchers examined if infections increase the risk of subsequent mental disorders in children and adolescents. They conducted a nationwide register-based cohort study consisting of 1,098,930 individuals born in Denmark between 1995 and 2012. Individuals with severe infections requiring hospitalizations displayed an increase in the risk of hospital contacts due to mental disorders by 84% and the risk of psychotropic medication use by 42%. Among individuals with less severe infection treated with anti-infective agents, the risks increased by 40% and 22%, respectively; the risks differed among specific mental disorders. These results cannot prove causality but do provide evidence for the involvement of infections and the immune system in the etiology of a wide range of mental disorders in children and adolescents.

Methods

• Analysis was performed from November 2017 to February 2018.
• All mental disorders diagnosed in a hospital setting and any redeemed prescription for psychotropic medication were identified for this study.
• The investigators performed Cox proportional hazards regression to report hazard rate ratios (HRRs), including 95% confidence intervals (Cis), adjusted for age, sex, somatic comorbidity, parental education, and parental mental disorders.

Results

• Researchers followed participants for 9,620,807.7 person-years until a mean (SD) age of 9.76 (4.91) years.
• They noted an association of infections requiring hospitalizations with subsequent higher risk of having a diagnosis of any mental disorder (n=42,462) by an HRR of 1.84 (95% CI, 1.69-1.99) and with higher risk of redeeming a prescription for psychotropic medication (n=56,847) by an HRR of 1.42 (95% CI, 1.37-1.46).
• Association of infection treated with anti-infective agents with higher risk of having a diagnosis of any mental disorder and with higher risk of redeeming a prescription for psychotropic medication was observed.
• Increased risk estimates were evident in association with antibiotic use.
• Mental disorders risk after infections increased in a dose-response association and with the temporal proximity of the last infection.
• Infections were associated with a risk of schizophrenia spectrum disorders, obsessive-compulsive disorder, personality and behavior disorders, mental retardation, autistic spectrum disorder, attention-deficit/hyperactivity disorder, oppositional defiant disorder and conduct disorder, and tic disorders.