Intelligence comes at a price. The human species, despite its talent for solving problems, has managed over the millennia to turn one of its most basic survival mechanisms–the stress response–against itself. “Essentially,” says Stanford University neurobiologist Robert Sapolsky, “we’ve evolved to be smart enough to make ourselves sick.”
In the 2008 National Geographic documentary Stress: Portrait of a Killer (above), Sapolsky and fellow scientists explain the deadly consequences of prolonged stress. “If you’re a normal mammal,” Sapolsky says, “what stress is about is three minutes of screaming terror on the savannah, after which either it’s over with or you’re over with.” During those three minutes of terror the body responds to imminent danger by deploying stress hormones that stimulate the heart rate and blood pressure while inhibiting other functions, like digestion, growth and reproduction.
The problem is, human beings tend to secrete these hormones constantly in response to the pressures of everyday life. “If you turn on the stress response chronically for purely psychological reasons,” Sapolsky told Mark Shwartz in a 2007 interview for the Stanford News Service, “you increase your risk of adult onset diabetes and high blood pressure. If you’re chronically shutting down the digestive system, there’s a bunch of gastrointestinal disorders you’re more at risk for as well.”
Chronic stress has also been shown in scientific studies to diminish brain cells needed for memory and learning, and to adversely affect the way fat is distributed in the body. It has even been shown to measurably accelerate the aging process in chromosomes, a result that confirms our intuitive sense that people who live stressful lives grow old faster.
By studying baboon populations in East Africa, Sapolsky has found that individuals lower down in the social hierarchy suffer more stress, and consequently more stress-related health problems, than dominant individuals. The same trend in human populations was discovered in the British Whitehall Study. People with more control in work environments have lower stress, and better health, than subordinates.
Stress: Portrait of a Killer is a fascinating and important documentary–well worth the 52 minutes it takes to watch.