New Genetic Clues to Posttraumatic Stress Disorder
Findings May Help Point the Way to Tests and Treatment for PTSD
A Biomarker for PTSD continued...
Then they tested their theory in animals. They removed the ovaries from rats and then replaced the lost estrogen in some of the animals but not others. After a few weeks, the rats exposed to estrogen had more of the peptide receptor genes than those who did not.
And in mice, they measured the levels of the PACAP receptors in the brains of the mice that were conditioned to respond to fear. After being exposed to fear, there were more PACAP receptors in their brains.
How Common Is the Gene?
In their traumatized population, Ressler says about 30% to 40% of people turned out to have at least one copy of the variant PACAP receptor gene and about 15% had two copies, a finding that indicates that inheriting the gene for this version of the PACAP receptor doesn’t make PTSD a given.
“In no way is this causal,” Ressler explains. “But it may help to divide risk vs. resilience.”
Ressler thinks PACAP is probably acting in concert with other genes in PTSD.
“It’s not the whole story,” he says. “We think it’s going to be one of a handful of these genes that together are acting on these pathways.”
One of the next steps, he says, will be trying to block the action of the receptor, perhaps with a drug, to see if they can expose animals to fear without giving them PTSD.
If that works, it may be the first step in the development of new treatments for the disorder, which often causes terrifying flashbacks, nightmares, depression, anxiety, memory problems, difficulty concentrating, numbness, and anger.
“The fear circuits in the brain are very highly conserved from humans all the way down to mice,” Ressler says. “So I personally think we’re going to understand the neurobiology of PTSD much faster than we do many other disorders, so for me, I certainly want to help come up with that.”