Short CommunicationHippocampal volume in vulnerability and resilience to depression

- Hippocampal volumes were assessed using a model based segmentation method.
- Reduced volume was found in individuals recovered from depression.
- Reduced hippocampus is a biological marker, or scar effect, of depression.
- No evidence to suggest volume change as vulnerability marker prior to illness onset.
- Increased volume was found in individuals who might have some resilience.

BackgroundReduced hippocampal volume has been associated with clinical depression. However, it remains unclear whether these changes are a biological vulnerability marker or a consequence of this disorder.Methods and results (Study 1)We first compared hippocampal volumes between (i) never-depressed individuals with elevated risk for depression by virtue of high neuroticism (ii) recovered depressed individuals with matched levels of neuroticism; and (iii) individuals with low neuroticism and no history of depression. We replicated the finding of reduced hippocampal volume in the recovered group; unexpectedly however, the never-depressed high-risk group showed an increase in volume. One hypothesis is that this group had a mean age above the typical onset age for depression; hence, these participants who have remained euthymic despite their personality risk might in fact possess some resilience.Methods and results (Study 2)A subsequent study was therefore carried out to compare hippocampal volume between high-neurotic vs. low-neurotic volunteers in a younger sample. No group difference was found.LimitationsThe present findings are limited by a small sample size; the cross-sectional design precluded us from makineg definitive conclusions about causal effect.ConclusionOur overall results suggest that reduced hippocampal volumes is a neural marker for the scar effect of depression, although this structural impairment could also be seen as a vulnerability marker for the development of future recurrent episodes. By contrast, larger hippocampal volumes could be a biological marker of resilience. These findings have clinical implications regarding treatment development for the prevention of illness onset and recurrent depressive episodes.