Medical Research: What is the background for this study?
Dr. Eliot: The hippocampus participates in many behaviors that differ between men and women, such as episodic memory, emotion regulation, and spatial navigation. Furthermore, the hippocampus is known to atrophy in diseases such as depression, anxiety disorders, and Alzheimer’s disease, all of which are more prevalent in women. It is conceivable that a premorbid difference in hippocampal volume contributes to females’ greater vulnerability. In the scientific literature, the hippocampus is often said to be proportionally larger in females than males. We set out to test this by doing a systematic review of the literature for hippocampal volumes in matched samples of healthy males and females, measured using structural MRI data collected from over 6000 participants of all ages.
Medical Research: What are the main findings?
Dr. Eliot: Raw hippocampal volume is reliably about 7% larger in men. However, in studies that correct for individual differences in total brain or intracranial volume (which is itself reliably larger in males), there is no sex difference in hippocampal volume. In other words, women do not have a proportionally larger or smaller hippocampal volume compared to men; this structure is basically the same in men and women.
Medical Research: What should clinicians and patients take away from your report?
Dr. Eliot: Beware of sex-typing your patients. Women and men are more similar than different at both the brain and behavioral level. Even the sex difference in depression and anxiety disorders is likely inflated by gender role behavior, such as men’s greater reluctance to admit feelings of weakness or fear.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: When considering sex difference in the human brain, it is crucial to test very large populations because the differences tend to be small.
Lise Eliot PhD (2015). Brains of Men and Women More Similar Than Different