Hippocampal subfield volumes and childhood trauma in bipolar disorders

Background: Alterations in hippocampal structure and function are present in bipolar disorder (BD). Childhood trauma is associated with risk for BD, and the several subfields of the hippocampus are differentially sensitive to the effects of stressors of the sort associated with risk for BD. The current study therefore sought to test the hypothesis that childhood trauma may be differentially associated with abnormal hippocampal subfield volumes in BD.

Methods: 104 participants with BD type I (BD-I, n = 56) or BD type II (BD-II, n = 48) and 81 healthy controls (HC) underwent high-resolution structural magnetic resonance neuroimaging. Hippocampal subfield volumes were determined using FreeSurfer. Childhood trauma was assessed with the Childhood Trauma Questionnaire (CTQ).

Results: There were significant effects of diagnosis on intracranial volume corrected hippocampal subfield volumes bilaterally as well as a significant interaction between diagnosis and childhood trauma. Hippocampal volumes did not differ between the BD-I and BD-II subgroups but hippocampal volumes were smaller in both groups when compared to HC. There was a significant effect of childhood trauma on bilateral presubiculum volume as well as significant interactions between diagnosis and childhood trauma on bilateral CA1, presubiculum and subiculum volumes, the direction of which differed between individuals with BD (larger) and HC (smaller).

Limitations: Recall bias may influence the reliability of the retrospective assessment of childhood trauma experiences.

Conclusions: Childhood trauma demonstrates differential effects on hippocampal subfield volumes of BD and HC, particularly in hippocampal subfields involved in emotion regulation.