Severe infectious diseases requiring hospitalization, as well as less severe infections treated with antimicrobials, may increase the risk of developing certain mental illnesses in childhood and adolescence.

It was previously known that infections are associated with an increased risk of schizophrenia and depression. But Danish scientists decided to investigate whether there is a link between any infections that require treatment and a wide range of mental disorders.

They conducted a cohort study* based on a nationwide registry that included 1,098,930 individuals born between 1995 and 2012. For each participant, severe infectious diseases requiring hospitalization and less severe infectious diseases for which antimicrobial agents were prescribed were recorded between birth and June 30, 2013. In addition, all mental disorders diagnosed in hospitals and any prescriptions for psychotropic medications were taken into account. Risk calculations were adjusted for age, gender, somatic comorbidities, and parental mental disorders.

It turned out that severe infectious diseases requiring hospitalization increased the risk of mental health visits by 84% and the risk of treatment with psychotropic medications by 42%. Less severe infections treated with antimicrobials increased these risks by 40% and 22%, respectively. The risk was highest among patients taking antibiotics (compared to antiviral, antifungal, and antiparasitic drugs), and the risk increased with the number of antibiotics a patient took.

The increased risk of developing mental illness can be explained by the influence of infectious agents and immune factors on the central nervous system. Furthermore, it is known that the state of the intestinal microflora can influence the development of mental health problems, particularly depression and schizophrenia**. Therefore, it is not surprising that taking antibiotics, especially multiple medications over long periods, can have a negative impact on a person's mental health.

* Köhler-Forsberg O, Petersen L, Gasse C et al. A Nationwide Study in Denmark of the Association Between Treated Infections and the Subsequent Risk of Treated Mental Disorders in Children and Adolescents // JAMA Psychiatry. Published online December 5, 2018. doi:10.1001/jamapsychiatry.2018.3428

** Severance EG, Yolken RH, Eaton WW. Autoimmune diseases, gastrointestinal disorders and the microbiome in schizophrenia: more than a gut feeling. Schizophr Res., 2016, 176(1):23-35. doi:10.1016/j.schres.2014.06.027