Contrary to the image of hardened drill sergeants molding untrained youths into skilled fighting machines, a Yale psychiatrist suspects that some soldiers may be born that way.

Charles A. Morgan III, M.D., associate professor of psychiatry, studied troops taking a rigorous survival course at Ft. Bragg, N.C., home to the XVIII Airborne Corps, to see whether some handled stress better than others. Working with researchers from the base, he found that the Army Special Forces, also known as Green Berets, consistently outperformed the other soldiers. When he looked at the levels of neuropeptide Y, a brain chemical that is linked to stress, he noticed that the Berets released higher levels during periods of stress and then returned to baseline more quickly once the stress was removed.

“As a group, the Special Forces were releasing so much more, we could identify who was in that unit just by looking at the numbers,” Morgan said. “The more neuropeptide Y they were releasing during stress, the fewer symptoms of confusion or mental disconnection during stress were reported.” During their training, soldiers are deprived of food and sleep, pursued through rough terrain by other soldiers acting as the enemy and, if “captured,” subjected to interrogation.

Morgan has published his research in several journals, most recently last year in Biological Psychiatry. But as soldiers prepared to go to war in Iraq in the spring, Morgan’s studies drew attention from the national press.

He says the question raised by his findings is whether the Special Forces soldiers have always released higher levels of the chemical or whether their training somehow enhanced their ability to do so. “I don’t think that’s likely. I think those guys are just different,” Morgan said, “but we’re still testing that hypothesis.”

Morgan’s findings could help the Army select the most likely candidates for dangerous duty, but there are also civilian applications. “Because we found that neuropeptide Y is low in people with anxiety disorders and depression, this raises the possibility of new ways of treating them. One might expect that pharmacologic agents that act as agonists at the npy-1 receptor might diminish anxiety,” he said.

Morgan is now looking at ways to help soldiers bounce back from stressful situations more quickly and manage stress more effectively so they don’t make costly—or deadly—mistakes.