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Researchers Find Higher Mental Illness Among City Dwellers

Researchers say living in a city increases the risk of developing a mental disorder, including depression and schizophrenia, compared to people who live in non-urban areas. The findings of the new study have implications for around half of the world's population who live in cities.

Previous studies have showed that city dwellers are 21 percent more likely than non-urban residents to develop an anxiety disorder and they have a 39 percent greater risk of for being diagnosed with a mood disorder.

There is even an increased risk of the brain disorder schizophrenia, in which patients suffer from delusions and hallucinations. Experts say the incidence of schizophrenia among those who are born and raised in cities is about two times that of people who live in non-urban areas.

Social scientists have argued that exposure to daily stress - such as traffic and toxic pollution - is responsible for the increased risk of mental illness among city dwellers, according to Jens Pruessner, director of McGill University's Centre for Studies in Aging in Montreal, Canada.

"Stress is of course defined in many different ways but one way to capture it is to say what are the daily hassles that you have to cope with? And you could imagine that if you live in the city, those might be by a large proportion as compared to someone who lives in a more rural environment," he said.

Pruessner's Center developed something called the Montreal Imaging Stress Task, or MIST, which was used as the protocol for a study of healthy German volunteers.

Participants were asked to do mathematical calculations while researchers took pictures of their brains using sophisticated imaging technology, and compared the brain images of volunteers who came from a city of more than 100,000 residents to those of volunteers who lived in rural areas.

Researchers found that urban living was associated with a greater stress response in a brain region called the amygdala, which is involved with emotional regulation and mood. And second brain region, called the cingulate cortex, which is associated with negative mood and stress, was found to be more activated in people who were brought up in cities, according to Pruessner.

"So even if you no longer live in the city but if you lived for the fifteen years of your life in the city, then this structure remains to be sensitized to stress," he said.

Both the amygdala and cingulate are known to be affected in people with mood disorders.
Pruessner says future research will focus on potential gender differences in how men and women process stress and how that might play a role in mental illness. "Women typically respond less strongly to stress. At the same time if men do get affected, then their disease progression for schizophrenia seems to be worse," he said.

An article describing the association between urban stress and mental disorders is published in the journal Nature.