There is an association between early childhood infections and attention-deficit/hyperactivity disorder, autism spectrum disorder, major depressive disorder, and schizophrenia. Moreover, the association cannot be attributed to genetic or psychosocial factors.
Putting It Into Practice
Proinflammatory cytokine levels provide a direct link between the response to pathogens and psychiatric disorders. Specifically, IL-1β, IL-6, and TNF-α are elevated during the acute phase of an infection, but are also elevated in patients with mood disorders, cognitive impairment, and behavioral problems.
These proinflammatory cytokines are known to influence circuits within the central nervous system, as well as neurotransmission and signaling. The proinflammatory cytokine levels remit during recovery from a psychiatric disorder, but persist in treatment-resistant cases.
Why this study matters
Immune dysfunction has been linked to psychiatric disorders based on genome-wide association studies, defective innate immunity at birth, the increased risk for psychiatric disorders following hospitalization in childhood for infections, and the increased prevalence of autoimmunity in patients with psychiatric disorders. Using a triangulation method, the current study confirmed the increased risk for psychiatric disorders following early childhood infection.
This was a case-cohort study involving patients who were born between 1981 and 2005 and diagnosed with attention-deficit/hyperactivity disorder and autism spectrum disorder with childhood infections before 5 years of age, and bipolar disorder, major depressive disorder, and schizophrenia with childhood infections before 10 years of age. Sociodemographic factors served as covariates in the analysis.
Results and conclusion
Early childhood infections were associated with an increased risk of attention-deficit/hyperactivity disorder (HR=1.29), autism spectrum disorder (HR=1.28), major depressive disorder (HR=1.23), and schizophrenia (HR=1.21). Similarly, exposure to a sibling with an infection during childhood was associated with an increased risk of attention-deficit/hyperactivity disorder, bipolar disorder, major depressive disorder, and schizophrenia.
Debost J-C, Thorsteinsson E, Trabjerg B, et al. Genetic and psychosocial influence on the association between early childhood infections and later psychiatric disorders. Acta Psychiatrica Scandinavica 2022; doi.org/10.1111/acps.13491.