Preexisting mental health problems could be setting soldiers up for post-traumatic stress disorder, or PTSD, when they return from the battlefield, U.S. Navy researchers said Monday.
They found those with depression, panic disorder or another psychiatric illness were more than twice as likely to develop the condition as their mentally stable peers.
"More vulnerable members of the deployed population might be identified and benefit from interventions targeted to prevent or to ensure early identification and treatment of post-deployment PTSD," Dr. Donald Sandweiss of the Naval Health Research Center in San Diego, California, and colleagues write.
Earlier studies have come to different conclusions, but their methods were less reliable than those used in the current one, the researchers add.
Between seven to eight percent of the general population eventually develops PTSD, according to the National Center for PTSD at the U.S. Department of Veterans Affairs.
The psychological toll - including flashbacks, "numbing" toward other people, and drug problems - can be extremely hard to deal with and may destroy relationships or cause trouble on the job.
While PTSD can be treated effectively with talk therapy, the military has also begun focusing on whether the problem might be prevented in the first place - for instance by identifying those at high risk and preparing them psychologically for conflict.
In the new study, published in the Archives of General Psychiatry, more than 22,000 soldiers completed a health questionnaire before they were deployed to Iraq or Afghanistan, and again after they returned.
Just over three percent had some mental illness, including PTSD, at the outset.
Upon returning, however, eight percent had symptoms of PTSD. Those who had mental illness other than PTSD before deployment had more than twice the odds of developing the condition after they got home.
Physical injuries during deployment were also tied to a higher risk, although much less so than preexisting mental health problems.