Medical researchers say they have discovered a possible "vaccine" for post-traumatic stress disorder that could protect soldiers in battle by regulating one of the body's own hormones.
Scientists at the Massachusetts Institute of Technology report in a new paper that ghrelin, a hormone produced during stressful situations, primes the brain for PTSD. They believe that by controlling ghrelin, they can also prevent the formation of PTSD after traumatic events.
"You would get a shot, and for a year it would lower your ghrelin levels," said Ki Gossens, assistant professor of brain and cognitive sciences at MIT, and an author of the paper in the journal Molecular Psychiatry, which is appearing this week. "When you were deployed and exposed to the stress of combat, your ghrelin levels would go up and the vaccine would combat that. That should reduce the incidence of PTSD. Right now, we don't have anything to prevent it."
Scientists had previously known that ghrelin makes you hungrier and dubbed it the "hunger hormone." It was the target of research by drug companies who wanted a cure for obesity, but none of that work was successful. However, Gossens said her group has found that ghrelin also may make people more susceptible to PTSD.
During their experiments, the researchers found that when rats were given a drug to stimulate ghrelin levels in the blood, they became much more susceptible to fear than normal rats. By blocking the receptors on the cells that interact with ghrelin, the researchers reduced fear to normal levels in the chronically stressed rats.
Gossens said that ghrelin operates alongside the brain's other "fight or flight" neurochemical system, which is controlled by the hormones cortisol and adrenaline. That signaling route is known as the hypothalamus-pituatary-adrenal pathway, or HPA.
"What we are suggesting is that the ghrelin pathway operates in parallel," Gossens said. "We think the emotional disorders (such as PTSD) following trauma exposure are the result of elevated ghrelin rather than HPA. It gives us a completely new set of targets to treat PTSD."
Gossens believes that since many ghrelin-related anti-obesity drugs have already passed federal human safety trials, it would give them a leg up on developing some kind of vaccine for PTSD. However at least one researcher said blocking ghrelin might have harmful side effects.
"As to the ‘vaccination' issue, it is premature to talk about that and probably also not a good idea," said Bruce McEwen, director of the neuroendocrinology laboratory at Rockefeller University in New York in an e-mail. "Ghrelin is a hormone and also a neuromodulator that stimulates appetite and also enhances aspects of cognitive function. A systemic vaccination might not even work and could ... make people anorectic and impair other aspects of physiology by blocking good actions of ghrelin."
Despite these reservations, McEwen said that the MIT paper "advances our knowledge by introducing a new player, ghrelin, in the fear and PTSD-related behavior story."
That might be some good news for sufferers of PTSD, a condition that has affected nearly 250,000 service members who fought in Iraq and Afghanistan since 2001.