Cities on the brain
Urban life takes mental toll; green space may cure it
CITIES HAVE been the engines of civilization for millennia, serving as places where the arts, commerce, and ideas flourish. The majestic imperial city of Rome defined the Roman empire. Paris gave the world impressionism. And New York — if you can make it there, you can make it anywhere.
But this jostling of people, products, and opinions can take a toll. Cities, recent research shows, can make us crazy.
Cities have always been held back by the toll they exact on their inhabitants. The close social interactions that make a city so productive also proved ideal for tuberculosis, measles, the plague, and many other diseases. In European capitals, circa 1800, deaths exceeded births; these cities only grew because of the influx of people from the countryside. An average man in 19th-century Paris was physically shorter than his rural counterpart.
Then came the “sanitation revolution,’’ which redesigned cities around the newly discovered principles of preventing infection. Today, raw sewage no longer flows down the Thames, and, amazingly, people of almost any country who live inside a city’s borders are generally healthier than those outside.
Yet cities still exact a mental toll. People living in an urban setting are 21 percent more likely to experience an anxiety disorder, and 39 percent more likely to experience mood disorders. City life roughly doubles the chances a person will suffer from schizophrenia, and this threat increases with time in cities, like the effect of an accumulating toxin.
Last week, German scientists announced that they had found, for the first time, the specific structures in the brain affected by city life. Using brain scanners, they demonstrated that people who lived in cities showed a greater stress response in the amygdala, a brain area that processes emotions. And a second structure, which helps regulate the amygdala, showed a heightened stress response in people who were raised in cities, according to a report in the journal Nature.
The discovery suggests a specific mechanism by which cities, with their steady stress, might unbalance parts of the mind. Scientists can now look at particular aspects of urban design — a particular layout of streets, say, or the preponderance of straight lines — to see which ones cause the signature brain changes. Andreas Meyer-Lindenberg, one of the German scientists who led the research, says he has already begun to look into just these sorts of questions.
One of the answers, it is already clear, will be to better integrate nature into our urban landscapes. In one experiment, led by the University of Michigan neuroscientist Marc Berman, people were given an demanding mental test and then told to go for a walk before being given the test again. A stroll through an arboretum brought a significant boost in test performance, but a walk on a busy Ann Arbor street did not. (Berman is now attempting to determine what particular aspects of nature account for the difference.)
This is part of a growing body of research proving that being in nature has a restorative effect on the brain. In 2010, researchers reviewed 25 studies of walking or running in green environments, and they found people experienced boosts in energy as well as reductions in anxiety, anger, fatigue, and sadness.
The good news, from an urban-planning point of view, is that it doesn’t take much nature. One classic study showed that patients with a window view of greenery recovered from surgery faster and needed less powerful pain medication.
The next step is to bring neuroscientists, psychologists, social scientists, architects, and others together, providing urban planners with the tools to design spaces that soften the city’s mental costs, support positive frames of mind and maximize the potential for creativity.
In the era of the Internet, it has become fashionable to argue that the importance of location is fading away. We can, after all, e-mail, chat, and video-conference from virtually anywhere on the planet. But to live in a place is to have your brain molded by it. This the both the promise and the threat of the cities of the future.