City dwellers are more likely to suffer stress and anxiety than people who live in the countryside because their brains are wired differently, scientists claim.
The experience of growing up in a city also increases the risk of developing schizophrenia, regardless of where you live in your later years, because of physical differences in how the brain works, research suggests.
While city life has previously been linked to anxiety and mood disorders, and the rate of schizophrenia is known to be higher in people born and brought up in cities, the findings are the first to show how specific brain structures are affected by urban life.
Researchers based in Germany asked 32 volunteers who lived and had been brought up in a variety of urban and rural areas to answer mathematical problems under time pressure.
The difficulty of the questions was varied to ensure a low success rate, and researchers gave negative feedback throughout the test to simulate social stress.
Brain scans showed that participants living in urban areas recorded higher levels of stress response in the amygdala, an area of the brain linked to anxiety disorders, depression and other types of behaviour associated with city life, such as violence.
The tests also showed that the longer a participant had lived in a city between birth and the age of 15, the higher the activity in the perigenual anterior cingulate cortex (pACC), a separate part of the brain that regulates stress.
In previous studies abnormal links between the pACC and amygdala have been observed in schizophrenia sufferers with no genetic vulnerability to the disease, suggesting factors such as environment may be linked.
In a paper published in the Nature journal, the researchers said there was a distinction between the effect of urban life on current city dwellers and those who lived there during childhood, which were "associated with mood and anxiety disorders and schizophrenia respectively."
The findings were checked against further samples using different tests to show that the unusual brain activity only occurred when the participants were under stress.