Jean Jacques Rousseau called cities “…the abyss of the species“. Well, they may not be that bad, but with their crowding and competition and noisy get-ahead in-your-face rat race environments, cities are certainly an experimental variable you might use to test the effects of stress. Which is what some researchers in Mannheim, Germany recently did. Their findings suggest that the 3.3 billion of us living in cities might consider official membership in Prozac Nation.
In a paper in Nature, “City living and urban upbringing affect neural social stress processing in humans” (abstract), the researchers tested a small group of volunteers (32), some of whom currently lived in cities, some of whom had grown up in cities but now lived in smaller towns, and some who had always lived in rural settings. The researchers stressed out the participants by making them work on really hard math problems while being constantly told they weren’t doing very well, or being told they doing so badly their poor results were ruining a really expensive experiment and could they please try harder. (Nice guys, huh!?) As this was being done the subjects’ brains were being monitored in a functional magnetic resonance imaging machine that could “see” which parts of the brain were active.
The current and former urban dwellers had different brain activity under stress from their non-urban counterparts. And the differences were centered on the amygdala and another brain area closely associated with the amygdala, the little section of specialized brain cells just above the brain stem where other research has found fear begins. The amygdala is your 24/7 “could there be danger out there?” radar. If it senses any kind of a threat, it sets off the hormonal, neurological, and metabolic processes that we think of as the Fight or Flight response, and which biologists call Stress. The urban brains in the recent research went off more readily, and more strongly, when stressed. Their sensitivity to stressors had been permanently set at a higher more hair-trigger level. And the bigger the city the person lived in, the stronger the heightened stress sensitivity. Rousseau might have been on to something.
This tiny study of 32 people is hardly enough to prove anything. But it’s another brick in a huge wall of evidence that finds that chronic stress does far more than cause a little heartburn. Chronic stress, the kind that lasts for more than a few days, has all kinds of profound impacts on your physical health, including, according to this study, changing your brain in ways that make you more sensitive to things that cause stress. The list of health damage from stress that lasts for more than a few days is long, and sobering.
- -Raises your blood pressure, and your risk of heart disease and stroke
- -Depresses your immune system. (The more worried you are about getting sick, the more likely it is that you will.
- -Suppresses memory, fertility, and growth (it can even permanently shrink the hippocampus, the part of the brain critical to the formation and recall of long term memory)
- -Is associated with higher likelihood of clinical depression, and Type 2 (adult onset) diabetes.
Studies on all sorts of species, including humans, have investigated the effects of crowding as a stressor. (Sound familiar, city dwellers?) Crowding causes many of the health effects listed above, in mice, rats, fish, dogs, monkeys, and you and me. Other studies have looked at people in unhappy marriages, at people living in poverty or in unhappy working conditions or who were raised by bad parents, and even at New Yorkers after the September 11, 2001 terrorist attacks, as examples of humans exposed to stress, and that research repeatedly finds an association between those stressors and one or more of the health effects described above. There is even a strong association between chronic stress and a greater likelihood of developing cancer (and a tougher time fighting it off) because stress weakens the immune system.
People live in a complex dynamic world, of course, not the controllable cages of a lab, so it’s hard for research on the health effects of stress to just study one discreet variable and say conclusively that Stressor A causes Health Effect B. In urban living, is it the crowding? The noise? The rat race pace and competition? It’s hard to know. But overall, the body of evidence establishes a frightening association between stress and all sorts of seriously bad health outcomes. The more stressed we are about things like unemployment and crime and pollution and food contamination and cancer, the more the worry itself becomes one of the biggest risks we face. And according to this recent study and many others, city living may be a stressor in and of itself.
So it may be true, not only for tourists but for urban dwellers as well, that cities are nice places to visit, but you wouldn’t want to live there.
(By the way, for a GREAT book on what stress can do to your health, treat yourself to the fun of Robert Sapolsky’s classic “Why Zebras Don’t Get Ulcers”. Hint. They have a Fight or Flight response, and either get away from the lion, or get eaten. They don’t stay stressed, like we do.)