Hippocampal subregion volumes and preadolescent depression risk in the ABCD sample.

The hippocampus is central in the pathophysiology of depression. Subregions of the hippocampus (head, body, tail) have been implicated in adult depression, though research examining depression and hippocampal subregions in youth has been limited. This study aimed to examine associations between preadolescent hippocampal subregions and depression risk as well as their interactions with factors associated with depression risk, including biological sex and socioeconomic status (SES). Hippocampal subregions were extracted from the Adolescent Brain and Cognitive Development Study baseline sample (N = 10,469, ages 9-10 years). Depression risk factors included maternal lifetime depression, child depressive symptoms, and child internalizing and externalizing symptoms. Maternal depression was measured through the Family History Questionnaire, and child symptoms were measured through the Child Behavioral Checklist. Results identified associations between hippocampal volumes and future increases in internalizing symptoms (N = 9738). Further, associations between hippocampal subregions and depression risk were moderated by biological sex and SES: males, but not females, with maternal depression exhibited lower hippocampal tail volumes (N = 9826), and for preadolescents with low, but not high, SES, greater hippocampal head volumes predicted increased internalizing symptoms at baseline (N = 10,294) and at the 24-month follow up (N = 7069-7086). Together, this study demonstrates the importance of hippocampal subregions within preadolescent depression risk and identifies subgroups, including preadolescent males and those with low SES, that may be at particular risk.