Living in the city or growing up in one can affect brain function during a stressful situation, a brain imaging study has found.
The world is becoming more urbanized, with almost 70 per cent of people expected to live in urban areas by 2050, according to projections by the United Nations.
Studies suggest that living in a city increases the risk of depression and anxiety, and that schizophrenia rates are higher in people born and brought up in cities. But until now, there hasn't been research into how human brain structures might be affected by urban living.
To that end, researchers at McGill's Douglas Mental Health University Institute in Montreal and the University of Heidelberg in Germany used MRIs to study brain responses of healthy German students who were taking a math test under stressful conditions.
Study participants faced time pressure and in some cases they had investigators scolding them through headphones.
When exposed to those stressful conditions, two areas of the students' brains that are known to be involved in processing emotions became more active, the researchers reported in Wednesday's online issue of the journal Nature.
Specifically, the brain's amygdala was more active in those who lived in cities, and the perigenual anterior cingulate cortex, or pACC, was more active in those who had been brought up in cities, the researchers found.
"Our results identify distinct neural mechanisms for an established environmental risk factor, link the urban environment for the first time to social stress processing, suggest that brain regions differ in vulnerability to this risk factor across the lifespan," Jens Pruessner of McGill and his co-authors concluded.