In the lab, Ben Sherwood (The Survivors Club) notes, it’s hard to study how people react to incredible stress. At Fort Bragg, it’s not so hard:
This is where the Army’s renowned survival school is located. It’s also where they believe in something called stress inoculation. Like vaccines, a small challenge or dose of a virus in your system prepares and defends you against a bigger challenge. In other words, they expose you to pressure and suffering in training so you’ll build up your immunity. It’s a kind of classic psychological conditioning: the more shocks to your system, the more you’re able to withstand.
Dr. Andy Morgan of Yale Medical School went there to learn who survives best under acute stress:
If you think it’s just training and the soldiers know they’re not really in serious danger, consider what Morgan discovered. During mock interrogations, the prisoners’ heart rates skyrocket to more than 170 beats per minute for more than half an hour, even though they aren’t engaging in any physical activity. Meanwhile, their bodies pump more stress hormones than the amounts actually measured in aviators landing on aircraft carriers, troops awaiting ambushes in Vietnam, skydivers taking the plunge or patients awaiting major surgery. The levels of stress hormones are sufficient to turn off the immune system and to produce a catabolic state, in which the body begins to break down and feed on itself. The average weight loss in three days is 22 pounds.
Morgan compared regular soldiers and Special Forces soldiers:
At the start or base line, the two groups were essentially the same, but once the stress began, and afterward, there were significant differences. Specifically, the two groups released very different amounts of a chemical in the brain called neuropeptide Y. NPY is an abundant amino acid in our bodies that helps regulate our blood pressure, appetite, learning and memory. It also works as a natural tranquilizer, controlling anxiety and buffering the effects of stress hormones like norepenephrine, one of the chemicals that most of us simply call adrenaline. In essence, NPY is one of the fire hoses that your brain uses to extinguish your alarm and fear responses by keeping the frontal-lobe parts of your brain working longer under stress.Morgan found one very specific reason that Special Forces are superior survivors: they produce significantly greater levels of NPY compared with regular troops. In addition, 24 hours after completing survival training, Special Forces soldiers returned to their original levels of NPY while regular soldiers were significantly below normal.
With so much more NPY in their systems, the Special Forces soldiers were much more clearheaded under interrogation stress and performed better according to the trainers. Special Forces soldiers really are special and different from the rest of the Army. They stay more focused and engaged in a crisis and bounce back faster afterward because their bodies produce massive amounts of natural anti-anxiety chemicals. In the fog of war — and everyday life for that matter — that’s a major advantage.
I’ve discussed neuropeptide Y and survival before. Morgan found that DHEA also plays a role:
In another arduous test, sailors are taken three miles off the Gulf Coast at night and are given a target destination on the beach. Dumped in the water, the students submerge and are not allowed to surface until they reach their objective. To make the challenge even more stressful, a clock is running and the divers aren’t allowed to go deeper than 25 feet. Despite the tides and currents, they’re also forbidden to swim parallel to the beach looking for their target. The penalty for breaking any of the rules is immediate expulsion from the course. Speed, efficiency and accuracy are a critical part of their grade.In this underwater navigation test as well as the exercise in the pool, Morgan found again that brain chemistry makes a big difference. The amount of NPY you pump is closely connected to your success—the more, the better. Morgan also found that the best underwater navigators release a lot of a natural steroid called DHEA, which buffers the effects of the stress hormone cortisol and helps the brain’s hippocampus with spatial relationships and memory. Divers with the most NPY and DHEA graduated at the top of the class. Those with the lowest amounts did poorly.
You don’t have to test obscure hormone levels to predict stress tolerance though; you can test for healthy heart-rate variation — or its absence:
Morgan analyzed the heartbeats of soldiers and sailors before they experienced major stress. Sure enough, the ones with metronomic heartbeats performed the best in survival school and underwater navigation testing. They also did the best in what’s called close-quarters combat training. Morgan analyzed their heart rates right before they went into mock battle. They were all suited up in combat gear, waiting for a buzzer to ring that would send them running into a building to “kill” the enemy and rescue hostages. (They use “simunitions,” simulated ammunition that hurts but doesn’t cause real harm.) The ones with metronomic heartbeats, Morgan says, shoot more bad guys and kill fewer hostages. Unfortunately, this metronomic effect is usually associated with early heart disease and even sudden death. Morgan wonders whether the same thing that makes you really good at surviving under high stress may not translate into excellent heart health when you’re 50. Without it, though, these elite forces might never even make it that far.