Hippocampal multimodal structural changes and subclinical depression in healthy individuals

Background Several neuroimaging studies report reduced hippocampal volume in depressed patients. However, it is still unclear if hippocampal changes in healthy individuals can be considered a risk factor for progression to clinical depression. Here, we investigated subclinical depression and its hippocampal correlates in a non-clinical sample of healthy individuals, with particular regard to gender differences. Methods One-hundred-two participants underwent a comprehensive clinical assessment, a high-resolution T1-weighted magnetic resonance imaging and diffusion tensor imaging protocol using a 3 T MRI scanner. Data of macro-(volume) and micro-(mean diffusivity, MD) structural changes of the hippocampus were analyzed with reference to the Beck Depression Inventory score. Results Results of multivariate regression analyses revealed reduced bilateral volume, along with increased bilateral MD in hippocampal formation predicting subclinical depressive phenomenology only in healthy males. Conversely, subclinical depressive phenomenology in healthy female was accounted for by only lower educational level, in the absence of any hippocampal structure variations. Limitations To date, this is the only evidence reporting a relationship between subclinical depressive phenomenology and changes in hippocampal formation in healthy individuals. Conclusions Our findings demonstrated that reduced volume, along with increased MD in hippocampal formation, is significantly associated with subclinical depressive phenomenology in healthy males. This encourages to study the hypothesis that early macro- and microstructural changes in hippocampi associated with subclinical depression may constitute a risk factor of developing depressive disorders in males.