Meditation changes hippocampal structure differently for men and women

The first sex-specific study of meditation’s effect on the brain structure known as the hippocampus has revealed differences between women and men.

In a study published in Frontiers in Psychology, researchers Eileen Luders, Paul M. Thompson, and Florian Kurth of UCLA used MRI scanning techniques to confirm that long-term meditative practice changes the anatomy of the hippocampus. The specific location of these changes differ between male and female meditators.

The hippocampus is a small brain structure integral to the limbic (emotion-motivation) system. It plays important roles in learning, mood, and the formation of memories. Neuroimaging studies from 2008 to the present have shown that meditation alters the make-up of the hippocampus.

For instance, hippocampi are larger in people who meditate and show denser cellular inner-connections. Levels of hippocampal gray matter—versatile neurons present in many brain systems, including motor function, memory, and perception—are also larger in people who routinely meditate.

In the current study, researchers hoped to see if anatomical differences between male and female hippocampi existed in participants who were long-term meditators. Their experimental group consisted of 30 people (15 male, 15 female, average age 47) all of whom had been meditating on a regular basis for an average of 20 years each. The control group had no consistent meditation practice. Researchers then achieved extremely accurate MRI readings of the subjects’ hippocampi on both micro- and macro-imaging levels.

The powerful degree to which researchers scanned and analyzed hippocampi revealed distinct anatomical and sex-specific differences. Confirming previous studies, both male and female meditators showed larger hippocampi with more abundant gray matter than their non-meditative counterparts. Specific change density in males, however, was “lateralized,” affecting both hippocampal heads, but with most change observed on the left hemisphere. Females showed more clusters of change specifically on the right hippocampal hemisphere.

This data reaffirms that meditation increases both men and women’s hippocampal size, and further reveals, for the first time, which specific surface structures are affected.

It is currently unknown which specific meditative or sex-specific mechanisms contribute to the development of these anatomical differences. Speculating the real-world effects of these differences, the authors cite a de Vibe et al. 2013 study, during which females in a “7-week mindfulness-based stress reduction” program were less mentally distressed at its conclusion than male program members. These sex-centered meditation outcomes could be linked to the specialized hippocampal changes found in women and not found in men.

While the current study cannot confirm this hypothesis, it certainly highlights the reality of sex-based hippocampal differences related to meditation. Further research and more refined MRI scans must be carried out to investigate how these sex-specific hippocampal structures come about.

The authors suggest longitudinal studies that track how hippocampal structure and meditation interact. This approach, plus the continued use of refined MRI scanning, may eventually capture the divergent ways men and women benefit from meditation practices.