Your brain is built to deal with stress that lasts about 30 seconds

You can feel your body responding to stress: Your pulse races, your blood pressure rises, and you feel a massive release of energy. That’s the famous hormone adrenaline at work. It’s spurred into action by your brain’s hypothalamus, that pea-size organ sitting almost in the middle of your head. When your sensory systems detect stress, the hypothalamus reacts by sending a signal to your adrenal glands, lying far away on the roof of your kidneys. The glands immediately dump bucketloads of adrenaline into your bloodstream. The overall effect is called the fight or flight response.

But there’s a less famous hormone at work, too—also released by the adrenals, and just as powerful as adrenalin. It’s called cortisol. You can think of it as the “elite strike force” of the human stress response. It’s the second wave of our defensive reaction to stressors, and, in small doses, it wipes out most unpleasant aspects of stress, returning us to normalcy.

Why do our bodies need to go through all this trouble? The answer is very simple. Without a flexible, immediately available, highly regulated stress response, we would die. Remember, the brain is the world’s most sophisticated survival organ. All of its many complexities are built toward a mildly erotic, singularly selfish goal: to live long enough to thrust our genes on to the next generation. Our reactions to stress serve the live-long-enough part of that goal. Stress helps us manage the threats that could keep us from procreating.

And what kinds of sex-inhibiting threats did we experience in our evolutionary toddlerhood? It’s a safe bet they didn’t involve worrying about retirement. Imagine you were a cave person roaming around the east African savannah. What kinds of concerns would occupy your waking hours? Predators would make it into your top 10 list. So would physical injury, which might very well come from those predators. In modern times, a broken leg means a trip to the doctor. In our distant past, a broken leg often meant a death sentence. The day’s climate might also be a concern, the day’s offering of food another. A lot of very immediate needs rise to the surface, needs that have nothing to do with old age.

Why immediate? Most of the survival issues we faced in our first few million years did not take hours, or even minutes, to settle. The saber-toothed tiger either ate us or we ran away from it—or a lucky few might stab it, but the whole thing was usually over in less than half a minute. Consequently, our stress responses were shaped to solve problems that lasted not for years, but for seconds. They were primarily designed to get our muscles moving us as quickly as possible, usually out of harm’s way. You can see the importance of this immediate reaction by observing people who cannot mount a thorough and sudden stress response. If you had Addison’s disease, for example, you would be unable to raise your blood pressure in response to severe stress, such as being attacked by a mountain lion. Your blood pressure would drop catastrophically, probably putting you into a state of debilitating shock. You would become limp. Then you would become lunch.

These days, our stresses are measured not in moments with mountain lions, but in hours, days, and sometimes months with hectic workplaces, screaming toddlers, and money problems. Our system isn’t built for that. And when moderate amounts of hormone build up to large amounts, or when moderate amounts of hormone hang around too long, they become quite harmful. That’s how an exquisitely tuned system can become deregulated enough to affect a dog in a metal crate—or a report card, or a performance review.

Learn more about Brain Rules.

BRAIN RULE RUNDOWN

Rule #8: Stressed brains don't learn the same way.

• Your brain is built to deal with stress that lasts about 30 seconds. The brain is not designed for long term stress when you feel like you have no control. The saber-toothed tiger ate you or you ran away but it was all over in less than a minute. If you have a bad boss, the saber-toothed tiger can be at your door for years, and you begin to deregulate. If you are in a bad marriage, the saber-toothed tiger can be in your bed for years, and the same thing occurs. You can actually watch the brain shrink.
• Stress damages virtually every kind of cognition that exists. It damages memory and executive function. It can hurt your motor skills. When you are stressed out over a long period of time it disrupts your immune response. You get sicker more often. It disrupts your ability to sleep. You get depressed.
• The emotional stability of the home is the single greatest predictor of academic success. If you want your kid to get into Harvard, go home and love your spouse.
• You have one brain. The same brain you have at home is the same brain you have at work or school. The stress you are experiencing at home will affect your performance at work, and vice versa.

View Stress and the brain tutorial

Stress at work video

Stress References (PDF)