Blood expression levels of genes targeted by the stress hormones called glucocorticoids could be a physical measure or biomarker for such people.

"We found that most of the genes and pathways that are different in PTSD-like animals compared to resilient animals are related to the glucocorticoid receptor," said lead investigator Rachel Yehuda, a professor of psychiatry and neuroscience at the Icahn School of Medicine at Mount Sinai University.

It suggests we might have identified a therapeutic target for treatment of PTSD, Yehuda added.

In lab experiments, researchers exposed a group of male and female rats to litter soiled by cat urine, a predatory scent that mimics a life-threatening situation.

They found that vulnerable rats exhibited higher anxiety and hyper arousal and showed altered glucocorticoid receptor signaling in all tissues compared with resilient rats.

Moreover, some rats were treated with a hormone that activates the glucocorticoid receptor called corticosterone one hour after exposure to the cat urine scent.

These rats showed lower levels of anxiety and arousal one week later compared with untreated, trauma-exposed rats.

"PTSD is not just a disorder that affects the brain. It involves the entire body, which is why identifying common regulators is a key. The glucocorticoid receptor is the one common regulator that consistently stood out," said co-investigator Nikolaos Daskalakis from Mount Sinai University.

PTSD symptoms may include flashbacks, nightmares and severe anxiety, as well as uncontrollable thoughts about the event.

The study appeared in the journal Proceedings of the National Academy of Sciences.

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