Reply to: Obsessive-Compulsive Disorder, Tic Disorders, and Early-Life Infections

In a Swedish, population-based birth-cohort study, Zhang et al. ( 1 Zhang T. Brander G. Isung J. Isomura K. Sidorchuk A. Larsson H. et al. Prenatal and early childhood infections and subsequent risk of obsessive-compulsive disorder and tic disorders: A nationwide, sibling-controlled study. Biol Psychiatry. 2023; 93: 1023-1030 Abstract Full Text Full Text PDF Scopus (6) Google Scholar ) found that antenatal maternal exposure and early childhood exposure to infections were each associated with an increased risk of obsessive-compulsive disorder (OCD) and tic disorders in later life. However, importantly, when siblings with versus without exposure to infection were compared, there was no significant difference in the risk of either OCD or tic disorders. Zhang et al. therefore concluded that familial, rather than infectious or autoimmune, factors appear to drive the risk of OCD and of tic disorders. Prenatal and Early Childhood Infections and Subsequent Risk of Obsessive-Compulsive Disorder and Tic Disorders: A Nationwide, Sibling-Controlled StudyBiological PsychiatryVol. 93Issue 11PreviewPostinfectious autoimmune processes are hypothesized to be causally related to both obsessive-compulsive disorder (OCD) and tic disorders, but current evidence is conflicting. This study examined whether prenatal maternal (and paternal, as an internal control) infections and early childhood infections in the offspring (i.e., during the first 3 years of life) were associated with a subsequent risk of OCD and Tourette syndrome or chronic tic disorder (TS/CTD). Full-Text PDF Open AccessReply to: Obsessive-Compulsive Disorder, Tic Disorders, and Early-Life InfectionsBiological PsychiatryVol. 93Issue 11PreviewWe thank Andrade (1) for his interest in our article (2) and for sharing his concerns about the interpretation of our findings. We indeed focused on severe infections requiring hospitalization. This was a deliberate design choice aimed at improving diagnostic validity. Similar design choices were made by others (3–6), with the additional advantage of facilitating comparisons across psychiatric disorders. As for the cutoff at age 3 years, this choice was admittedly arbitrary and aimed at identifying early-life exposures that, together with in utero infections, represent exposures occurring during a period considered critical for neurodevelopment (7,8). Full-Text PDF