State-dependent changes in hippocampal grey matter in depression

Area of Science:

• Neuroscience
• Psychiatry
• Neuroimaging

Background:

• Reduced hippocampal volume is associated with depression and relapse vulnerability.
• Neuroplasticity in the hippocampus after antidepressant treatment is known in animals but not humans.
• The role of hippocampal grey matter changes in depression requires further investigation.

Purpose of the Study:

• To determine if hippocampal grey matter loss is present in medication-free depressed patients.
• To investigate if hippocampal volume changes in response to antidepressant treatment.
• To assess if hippocampal grey matter reduction is a stable trait in remitted patients.

Main Methods:

• Structural magnetic resonance imaging (MRI) was used in a cross-sectional and longitudinal design.
• Voxel-based morphometry (VBM) with Diffeomorphic Anatomical Registration Through Exponentiated Lie algebra (DARTEL) was employed to measure grey matter concentration.
• Sixty-four unipolar depressed patients (39 currently depressed, 25 in remission) and 66 healthy controls were studied. 32 depressed patients received 8 weeks of citalopram treatment.

Main Results:

• Currently depressed patients showed bilateral hippocampal grey matter reduction compared to healthy controls and remitted patients.
• No significant difference in hippocampal grey matter was found between healthy controls and medication-free remitted patients.
• Hippocampal grey matter volume increased after 8 weeks of citalopram treatment in currently depressed participants.

Conclusions:

• Hippocampal grey matter reduction is specific to the depressed state, not a stable trait in remission.
• This grey matter reduction may serve as a biomarker for a depressive episode.
• Antidepressant treatment can induce adaptive neuroplastic changes in the human hippocampus.