Smaller hippocampal volumes predict lower antidepressant response/remission rates in depressed patients: A meta-analysis

Whether hippocampal volume predicts response and/or remission after antidepressant treatment of Major Depressive Episodes (MDE) in Major Depressive Disorder (MDD) remains unclear. We meta-analyzed prospective studies comparing baseline hippocampal volume in patients with or without response/remission after antidepressant treatment. Pubmed, Embase and Google Scholar were searched for studies of patients with current MDE in MDD, with hippocampal volume assessments at baseline, initiation of antidepressant drug treatment, and prospective assessment of response/remission after treatment. Six studies (374 patients), of which 2 were positive and 4 negative, were meta-analyzed. Compared to responders/remitters, patients who failed to achieve response/remission had smaller total hippocampus volumes at baseline (mean volume difference = 260 mm3, CI95% [93; 427], p= 0.002). These results remained significant in patients under 60 years of age (p = 0.02), in those over 60 years old (p = 0.04), and for right (p = 0.006) and left (p = 0.02) hippocampi. The probability of non-response/non-remission was 68.6% for patients with a total hippocampal volume at least 10% lower than the average, and 47.1% for patients with a total hippocampal volume 10% higher than the average. In depressed patients treated with antidepressant drugs, smaller hippocampal volumes predict lower response/remission rates.