London: It may not come as a surprise to urbanites -- living in big cities is more stressful and could lead to depression, claims a new study.
Previous studies have showed that those born and bred in cities were more likely to suffer anxiety or mood disorders than those brought up in the countryside.
 The biological reasons were unknown, but the new study found that the parts of the brain dealing with stress and emotion are affected by living among the crowds in cities than in rural areas.
The findings, according to the researchers, can shed light on why city dwellers are more prone to anxiety, schizophrenia and depression than their rural counterparts, the Daily Telegraph reported.
For the study, the scientists at the Douglas Mental Health University Institute in Germany carried out a series of brain scans of healthy volunteers from rural and urban areas.
The brain activities of adult volunteers are monitored while they carried out mental arithmetic puzzles under time pressure.
The scans revealed that city residents place more stress on the amygdala, which is involved with emotional regulation and mood, whereas country dwellers show more activity in the cingulate cortex -- associated with regulating stress, the researchers report in the journal Nature.
 Lead researcher Dr Jens Pruessner said: "Previous findings have shown that the risk for anxiety disorders is 21 per cent higher for people from the city, who also have a 39per cent increase for mood disorders.
"In addition, the incidence for schizophrenia is almost doubled for individuals who are born and brought up in cities. These values are a cause for concern and determining
the biology behind this is the first step to remedy the trend."

He said: "These findings suggest that different brain regions are sensitive to the experience of city living during different times across the lifespan.
 "Future studies need to clarify the link between psychopathology and these affects in individuals with mental disorders.
"These findings contribute to our understanding of urban environmental risk for mental disorders and health in general.
They further point to a new approach to interface social sciences, neurosciences and public policy to respond to the major health challenge of urbanisation."