In the first study of its kind, scientists looked at more than 7,800 MRI scans from people in 29 different countries. In countries where there was greater gender inequality, the cortical thickness of the right hemisphere of women’s brains was thinner than men’s. In more gender equal countries there was no significant difference.
The areas of the brain affected were those particularly associated with stress and emotions.
Lead author Dr Nicolas Crossley, Visiting Professor in the Department of Psychiatry at the University of Oxford and Associate Professor in the Pontificia Universidad Católica in Chile, said:
"Our analysis suggests some sex differences in brain structure are associated with the adverse social environment under which many women live.
“These changes were particularly located in brain regions involved in control of emotions and that are also affected in stress-related disorders such as depression and post-traumatic stress disorder. We therefore think that what we are seeing is the effect of chronic stress in women’s brains in gender unequal environments. Stress affects neurons’ connections, which we would then see as thinning of the grey matter cortex in MRI studies. However other mechanisms could also be involved, such as the effect of reduced opportunities including education in women’s brains, leading to lower development of connections.
Our analysis suggests some sex differences in brain structure are associated with the adverse social environment under which many women live."
“These results suggest a potential neural connection between gender inequality and higher risks of mental health problems and reduced academic performance - pointing to the potentially hazardous effect of gender inequality on women’s brains.
“This research has the potential to inform gender equality policies but needs further study to help examine in greater details how and when this happens."
The researchers looked at MRI scans from 4,078 women and 3,798 men aged between 18 and 40 from countries including the UK, the US, China, Latin America, India and South Africa.
The paper, published in the journal Proceedings of the National Academy of Sciences, was a collaboration between dozens of academics affiliated to more than 70 institutions.
Gender inequality was measured using the United Nations’ Gender Inequality Index and the World Economic Forum’s Global Gender Gap Index.