Hippocampal Size May Predict Depression Treatment Effectiveness

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Electroconvulsive therapy (ECT) has recently gained attention for its ability to reduce depression symptoms in many individuals who are treatment to more traditional methods. Now, new research published in Biological Psychiatry indicates hippocampal structure could be a useful indicator of which individuals with major depression are most likely to benefit from the treatment.

amygdala and hippocampusResearchers from the University of California, Los Angeles (UCLA) found that patients for major depression who had smaller hippocampal volumes at baseline testing were notably more likely to show clinical improvement after the first phase of ECT treatment.

“Smaller hippocampal volumes at baseline predict a more robust clinical response,” first author Shantanu H. Joshi, PhD, assistant professor of neurology at UCLA, said in a statement. The researchers hope the results help pave the path for more tailored treatment plans for people experiencing depression.

“ECT is a fast-acting treatment recommended for patients who have failed to respond to antidepressants and other pharmacological interventions,” said Dr. Joshi. “A few preliminary studies by other researchers have shown effects of ECT on brain structure. However, the patient population size was small, and the studies did not show relationships with clinical response. Our study looked at a much larger sample size of patients to date.”

For the study, 43 patients receiving ECT for a major depressive episode also underwent 3T magnetization – prepared rapid gradient-echo MRI to assess changes in hippocampal and amygdala structures. Scans were taken before treatment begins, after the second ECT session, and within 1 week of completing treatment.

All participants were experiencing a major depressive episode, as determined on the basis of DSM-IV-TR diagnostic criteria, and had experienced two or more major depressive episodes in the past and had failed to respond to at least two prior standard antidepressant treatments.

These participants were compared to 32 healthy control participants, who were imaged twice and compared against those who underwent ECT.

The published results showed that hippocampal volumes of the depressed participants were smaller at baseline compared to control participants. The researchers also noted both hippocampal and the amygdala volumes increased following ECT in relation to symptom improvement. To the researchers, this suggests baseline hippocampal volume could predict clinical response.

Dr. Joshi noted that “significant changes in both clinical scores and hippocampal and amygdalar volume are immediately observable after the second ECT session (within ~72 hours of treatment initiation). Further, the increases in volume with ECT show concomitant improvements in clinical symptoms.”

The hippocampus is essential for learning and memory, while the amygdala is linked to emotional regulation, decision making, and memory. Past research has already found reductions in hippocampal volume linked to major depressive disorder.

“ECT elicits neuroplastic processes associated with clinical response that act to normalize MDD-related reductions in hippocampal and amygdala structure. Patients with smaller relative hippocampal volumes are most likely to show volume increases and improved clinical response. Thus variations in hippocampal and amygdala structure may serve as potential biomarkers for the development of other fast acting treatments,” the investigators write.

Going forward, studies such as ours are the first step towards exploring the idea of adult human neurogenesis as a mechanism for treatment efficacy in depression,” Joshi concluded.

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