Evidence links urban dwelling to mental health

NEW YORK - This may come as no surprise to residents of big cities: Living there can be bad for your mental health.

Now researchers have found a possible reason why. Imaging scans show that in city dwellers or people who grew up in urban places, certain parts of the brain react more vigorously to stress. That may help explain how city life can raise the risks of suffering from schizophrenia and other mental disorders, researchers said.

Previous research has found that growing up in a big city raises a person's chances of suffering from schizophrenia. And there's some evidence that city dwellers are at a greater risk of having mood and anxiety disorders, although the evidence is mixed.

In any case, the volunteers scanned in the new study were healthy, and experts said that while the differences noticed in brain activity were interesting, the study fell short of establishing a firm tie to mental illness.

The study, conducted in Germany and published in an issue of the journal Nature released on Thursday, looked at how the brain reacts to stress caused by other people.

To do that, investigators had volunteers lie in a brain scanner and solve math problems. The volunteers expected easy problems, but they were in fact hard enough that each volunteer ended up getting most of them wrong.

While in the scanner, volunteers heard a researcher criticize their poor performances, saying they were surprisingly bad and disappointing, and telling the volunteers they might not be competent to participate.

An initial study with 32 volunteers found city-urban differences in two brain regions. One was the amygdala, which reacts to threats in one's environment, and the other was the circuitry that regulates the amygdala. Researchers found that volunteers from cities of more than 100,000 showed more activation of the amygdala than participants from towns of more than 10,000, and those in turn showed more activation than people from rural areas.

To assess any effect of where the volunteers grew up, the researchers assigned each an "urbanicity" score based on how many years they'd spent by age 15 in a city, town or rural area. The higher the score, the more urban their childhood life was, and the more activity showed up in the amygdala-regulating circuitry during the experiment.

A slightly different stress-producing test yielded similar results from a separate group of 23 volunteers.

But when a third group of 37 adults performed mental tasks without being criticized, no differences appeared between those hailing from urban and rural places. That showed the effects largely came from the criticism.

Associated Press