Early life exposure to infection, anti-infectives and altered immune activity have been associated with elevated risk of
some psychiatric disorders. However, the risk from exposure in fetal life has been proposed to be confounded by
familial factors. The hypothesis of this study is that antibiotic drug exposure during the fetal period and the first two
postnatal years is associated with risk for later development of psychiatric disorders in children. All births in Finland
between 1996 and 2012, 1 million births, were studied for antibiotic drug exposure: mothers during pregnancy and
the children the first two postnatal years. The children were followed up for a wide spectrum of psychiatric diagnoses
and psychotropic drug treatment until 2014. Cox proportional hazards modeling was used to estimate effects of
antibiotic drug exposure on offspring psychiatric disorders. Modestly (10–50%) increased risks were found on later
childhood development of sleep disorders, ADHD, conduct disorder, mood and anxiety disorders, and other
behavioral and emotional disorders with childhood onset (ICD-10 F98), supported by increased risks also for childhood
psychotropic medication. The prenatal exposure effects detected were not explained by explored familial
confounding, nor by registered maternal infections. To conclude, this longitudinal nation-wide study shows that early
life antibiotic drug exposure is associated with an increased risk for childhood development of psychopathology.
Given the high occurrence of early-life antibiotic exposure, these findings are of public health relevance. Whether the
associations reflect effects of the antibiotic drug use or of the targeted infections remains to be explored further.