Unthinkable_ Who Survives When Disaster Strikes - and Why - Amanda Ripley [57]
In 1975, Jerry was diagnosed with Vietnam Stress Syndrome. But no one seemed to know how to help him. After a bad experience at a veterans’ hospital in Waco, Texas, he didn’t seek out help again until 1992. He joined a program for vets with posttraumatic stress disorder, as it’s now called, at the Veterans Administration Hospital in Oklahoma City, Oklahoma. He drove two hours there and back for six weeks because he was finally getting the treatment he needed.
In the mid-1990s, scientists discovered that people with posttraumatic stress disorder didn’t just behave differently; their brains actually were different. The hippocampus, located deep within the brain near the amygdala, was a little smaller in people with posttraumatic stress disorder. The hippocampus is intimately involved in learning and memory, and it helps us decide whether something is safe or not. In a disaster—and afterward—it can boost our resilience. (London cab drivers, who must memorize all the city’s streets, have unusually large hippocampi.) Most scientists assumed that trauma had shrunk the hippocampus of the people with posttraumatic stress disorder. After all, that was what happened when animals were exposed to extreme stress: the hippocampus got smaller. But no one really knew for sure.
In 1998, the Thompsons got a phone call about an ingenious plan to study Vietnam veterans with twin brothers. Psychologist Mark Gilbertson and his colleagues at the Veterans Administration Medical Center in Manchester, New Hampshire, wanted to study the human brain before and after trauma. They wanted to see if people who developed posttraumatic stress disorder had started life with different brain structures than those who had not developed the disorder. In particular, they wanted to measure the hippocampus—the part of the brain that helps process danger signals and that is believed to be involved in dissociation.
Of course, it is hard (and extremely expensive) to track a large sample of people for decades. So Gilbertson and his team came up with a way to essentially turn back time on Vietnam vets. They would study sets of twins—in which one brother had gone to war and one hadn’t. “It was a good analog for looking at this chicken and egg problem,” he says. Through the Veterans Administration’s twin registry, Gilbertson and his colleagues painstakingly tracked down eighty men like Jerry and Terry. It took three years to find and test them all, but it was a beautiful sample. Because they were identical twins, the size of the brothers’ hippocampi should have been the same—unless some kind of trauma had altered their brains’ terrain after birth. In other words, the brain of the nonveteran twin provided a snapshot of the brain of the veteran before he went to war. The sample included seventeen men who had developed posttraumatic stress disorder in Vietnam (and their seventeen brothers without combat experience); the rest of the vets and their brothers had never developed the disorder at all.
Two by two, the brothers flew in from around the country to Manchester or Boston to have their brains imaged through an MRI. “That was sort of fascinating,” Gilbertson says. “Most of these guys, even in their fifties, looked so much alike. As soon as they’d come in, I’d have to tag a piece of clothing so that I could tell them apart.” Many of the nonveterans saw the study as a sort of reunion and a way to serve their brothers who had been damaged by war. For some of the veterans, the process itself was a trial. Going through the claustrophobic MRI machine caused a spike in anxiety. The healthy brothers were in turn very protective of their twins. “Some of the brothers would stand guard at the foot of the MRI while their brother was undergoing the procedure,” Gilbertson remembers.
Jerry and Terry flew to Boston together for the study. They stayed at the Holiday Inn at Logan Airport and had a fine time until Jerry had to actually get inside the MRI machine. The loud banging sound inside the machine sounded just like a .60-caliber gun. He had a flashback of being on a helicopter