GENDER INEQUALITY LINKED TO STRUCTURAL DIFFERENCES IN MEN AND WOMEN’S BRAINS

A new global study has found that gender inequality is correlated with differences in men and women’s brain structure. The findings suggest that in countries with higher levels of gender inequality, women have thinner cortices, particularly in the right hemisphere.

This meta-analysis of 139 previously conducted studies, utilised 7,879 MRI scans of healthy men and women from 29 different countries, including the UK, China, India and USA. Gender inequality for each country was quantified using an aggregate of measures such as political representation, educational attainment and health.

The results revealed that in countries with low gender inequality, there were no differences in cortical thickness between men and women. However, in countries with high gender inequality, women showed a negative correlation between gender inequality and cortical thickness in three specific brain areas: the caudal anterior cingulate gyrus, orbitofrontal gyrus, and lateral occipital cortex. These associations remained significant even after accounting for GDP per capita.

Importantly, these three brain structures have been linked to emotional control functions such as: resilience to adversity, responses to inequity and negative social comparisons; as well as mental health disorders like depression and PTSD. Therefore, these results could provide a socio-physiological explanation for the higher prevalence of mental health issues in women, although further research is needed to establish causality.

A successful feature of this research is its global focus (35% of participants from low and middle-income countries), helping address the criticism of much psychological research being biased toward white, high-income, Western populations. That said, only MRI images from India represented the lowest income groups. Whilst US and Chinese samples are overrepresented in the data, the results remain significant even when these two countries are not included. Furthermore, comparing male and female scans at each location rather than worldwide, reduces confounding factors such as socio-economic background or quality of MRI.

Several mechanisms could explain these findings. High-stress is known to impact neuronal connections and so if unequal societies cause high-stress in women, this may result in reduced cortical thickness in women. Alternatively, limited educational opportunities for women in unequal societies may hinder neuroplasticity and the development of new neuronal connections. Either way, the research is an important development in understanding and combatting mental health challenges worldwide.