Stress hormones, genetics and childhood events are among the factors that could influence a person's risk of developing post-traumatic stress disorder (PTSD), according to research presented at the annual meeting of the American Association for the Advancement of Science.
One study of US military personnel who were exposed to highly stressful situations found differences in stress hormone levels.
"Interestingly, there are some individuals who, when confronted with extreme stress, their hormone profile is rather unique," said Yale University psychiatrist Deane Aikins, Agence France Presse reported.
"It doesn't reach the same peak as the rest of us. So we are ready to scream in our chair, and there are certain individuals who just don't get as stressed. Their stress hormones are actually lower and the peptides that down regulate that stress are quite higher."
Low IQ as early as age five, difficult temperament at age three, and family factors such as growing up in poverty, having a depressed mother or being separated from parents at a young age could all increase a person's risk of developing PTSD, found Harvard University public health professor Karestan Koenen and colleagues, AFP reported.
Also, "some people have genetic variants that make them more vulnerable to the effects of trauma," Koenen said.
Another study found that Vietnam veterans who suffered injuries in a certain area of the brain didn't develop PTSD.
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