For the new analysis, published online in Sleep Health, researchers first surveyed 928 veterans on National Guard bases in Hawaii and New Mexico who had been deployed to Iraq, Afghanistan, Somalia or other war zones. More than 90 percent were male.

More than half of them reported some degree of sleep problems after returning home, including trouble falling or staying asleep followed by feeling irritable or having angry outbursts.

Researchers then identified a subset of 101 veterans who had symptoms associated with posttraumatic stress disorder or substance use disorders and interviewed them face-to-face. In this group, the rate of sleep problems after deployment was 81 percent.

Many of these soldiers still felt vulnerable after their deployment. Five respondents told researchers they slept with a gun under their pillow, or elsewhere in the bed. One slept on the living room couch because he felt the need to guard his house.

The researchers noted that one veteran was so anxious he "found his bedroom at home too big to feel comfortable, so he slept in the closet that adjoined it."

The researchers asked 78 of these individuals to discuss their strategies for managing their sleep problems. Twenty-three resisted treating their insomnia with prescription drugs because they feared becoming dependent or worried it would impair their thinking or stigmatize them. They used over-the-counter-medicines, including cold medicine, to help them fall asleep. Sixteen soldiers used alcohol to help them get to sleep and to control their nightmares, while 18 used prescription sleep aids. Other approaches included making adjustments to sleeping arrangements or schedule, watching television or playing video games, and exercising.

"All branches of military personnel are prone to having sleep issues after deployment which means they're also more prone to mental health problems. Military culture has a tendency to stigmatize servicemen and women who receive services for mental or behavioral problems," lead author Martha Lincoln of San Francisco State University told Reuters Health in a telephone interview.

"We hope the impact of this research will be to add to the evidence base for military intervention and health policy so there can be upstream awareness of how insomnia is affecting people," she said.

Philip Gehrman, a sleep medicine specialist at the University of Pennsylvania in Philadelphia, told Reuters Health by phone, "Military training teaches soldiers to keep one eye open and be alert at all times. There's no subsequent retraining that takes place after deployment to unlearn those patterns."

"This study highlights the important aspects of persistent sleep problems that often go unaddressed, but that really take a toll on people's lives," said Gehrman, who wasn't involved in the new research.

Michael Twery, director of the National Center on Sleep Disorders Research at the National Heart, Lung and Blood Institute in Bethesda, Maryland, told Reuters Health by phone that while the study was a small one and needs to be replicated in larger groups of soldiers, it "(lays) a foundation to help us design more definitive studies of sleep in this population."

"There's a big gap in understanding the relationship between insufficient sleep and public health," said Twery, who also wasn't a part of the study.