Structural changes in the hippocampus in major depressive disorder: contributions of disease and treatment

Area of Science:

• Neuroimaging
• Psychiatry
• Neuroanatomy

Background:

• Previous magnetic resonance imaging (MRI) studies indicate reduced hippocampal volume in patients with major depressive disorder (MDD).
• Recent research investigates if specific hippocampal subregion volumes are associated with MDD.
• This study aims to clarify subregional hippocampal volume changes in MDD using advanced MRI techniques.

Purpose of the Study:

• To investigate volumetric differences in hippocampal subregions (head, body, tail) between patients with MDD and healthy controls.
• To explore potential correlations between hippocampal subregion volumes and medication status in MDD.
• To identify if observed hippocampal changes in MDD are trait-dependent or treatment-dependent.

Main Methods:

• Utilized a 3D tracing protocol for detailed delineation of hippocampal subregions.
• Recruited 39 MDD patients (16 medicated, 23 unmedicated) and 34 healthy controls.
• Acquired high-resolution MRI scans (1.5 mm x 0.5 mm x 0.5 mm) on a 1.5-T scanner and performed blinded volumetric analyses adjusted for intracranial volume.

Main Results:

• MDD patients exhibited significantly reduced bilateral hippocampal tail volumes.
• A reduction in the right hippocampal head and right total hippocampus volume was observed in MDD patients.
• Medicated MDD patients showed increased hippocampal body volume compared to healthy controls and unmedicated MDD patients.

Conclusions:

• Reduced hippocampal tail and head volumes in MDD may represent trait markers.
• Hippocampal body volume changes appear to be influenced by antidepressant treatment.
• Further prospective studies are necessary to confirm the direct impact of antidepressant treatment on hippocampal volume in MDD.