A Study of the Bidirectional Association Between Hippocampal Volume on Magnetic Resonance Imaging and Depression in the Elderly

Background: Hippocampal volume loss on magnetic resonance imaging (MRI) has been reported in patients with depression. It is uncertain whether a small hippocampus renders a person vulnerable to develop depression or whether it is a consequence of depression. In this study, we addressed whether smaller baseline MRI hippocampal volumes increase the risk of incident depression. We also examined whether depressive symptoms at baseline were associated with decline in hippocampal volume during follow-up.

Methods: Data were obtained in a prospective population-based study over a 10-year period. A sample of 514 nondemented persons aged 60 to 90 years underwent baseline measurements in 1995-1996 including three-dimensional MRI scans for assessment of hippocampal volumes and depressive symptoms (measured with Center for Epidemiologic Studies Depression Scale). Follow-up MRIs were made in 1999-2000 and in 2006. Incident depression was identified through standardized psychiatric examinations and continuous monitoring of medical and pharmaceutical records.

Results: During a mean follow-up of 6.8 years per person (range .07-10.01 years), 135 of the 514 persons developed a clinically relevant episode of incident depressive symptoms. There was no association between baseline hippocampal volumes and incident depression (hazard ratio per SD decrease of average hippocampal volume .98 [.81-1.19], p = .84). A baseline Center for Epidemiologic Studies Depression Scale score of 16 or higher predicted a faster rate of decline in hippocampal volume. Also, incident depression was accompanied by a faster decline in left hippocampal volume.

Conclusions: This study provides no evidence that a small hippocampal volume precedes the development of late-life depression. Depression, however, may lead to a faster rate of hippocampal volume decline.