According to a study reported in the science journal Nature, city-dwellers are more prone to mental disorders than those living in villages and smaller towns.

Psychiatrist Andreas Meyer-Lindenberg and collaborators at the Central Institute of Mental Health and the University of Heidelberg Medical Faculty in Mannheim, Germany recruited 32 volunteers from cities, towns and villages and asked them to work on difficult arithmetic problems while monitoring brain activity. Meyer-Lindenberg found that that volunteers who currently lived in a city exhibited greater activity in the amygdala -- the brain part that is overactive in persons with social anxiety disorder. He also found that those raised in a city showed more activity in the perigenual anterior cingulate cortex (pACC), a region that has been implicated in some studies on schizophrenia.

The results of the initial study encouraged Meyer-Lindenberg to conduct a further study, this time with visual cues of scientists frowning at those working on the problems. Again they found a greater stress response in those volunteers who lived in the city. According to Nature, even the most powerful gene linked to schizophrenia only conveys a 20 percent increased risk. But the disease is twice as common in those who are city-born and raised as in those from the countryside, and the bigger the city, the higher the risk.

However, the small sample size means that the results so far are not conclusive.

The team now plans to conduct similar studies on the general population and on immigrants to map the connection between social isolation and mental illness.

While epidemiologists have long sought out -- and proven -- the link between the mental illness and the attendant stresses of city life, neuroscientists have thus far stayed away from such studies. This is perhaps the first study of its kind by a psychiatrist.