Last year, a record number of active-duty service members 349 committed suicide, according to the Associated Press. The number far exceeded the number of combat deaths in Afghanistan last year.
Harry Croft, a former Army doctor and a psychiatrist who has evaluated more than 7,000 veterans with post-traumatic stress disorder, said such studies are important because the causes of suicide are not fully understood.
"It's not just combat, we know that. So what else is there?" said Croft, who co-authored the 2011 book, "I Always Sit with My Back to the Wall."
"This whole suicidal plague a lot of it is about relationships," he said. "The more research that is done into what is causing this epidemic among the military and veterans, the better."
The study surveyed 273 airmen at two bases Moody Air Force Base in Georgia and Lackland Air Force Base in Texas and 309 undergraduate college students. It was published online Jan. 17 in the journal "Suicide and Life-Threatening Behavior."
Bryan, the lead author, said he was most surprised by the high correlation between assault on adult military members and suicidal thoughts. "I don't think we've talked about that," he said.
Though the link between rape and suicidal thoughts is interesting, it would take a bigger sample to draw meaningful conclusions, he said. Of the 273 airmen in the study, fewer than 50 were women, and women are more often the victims of sexual attacks.
The finding, though, does not surprise Breeze Hannaford, a therapist at the Veterans Affairs hospital in Salt Lake City.
"The majority of people I deal with have attempted suicide and they feel it's related," said Hannaford, the military sexual assault coordinator at the George E. Wahlen Department of Veterans Affairs Medical Center.
In her experience, the impact is worse when a service man or woman is assaulted by a fellow soldier or superior. "The higher the level of betrayal, the higher the level of trauma."
The biggest implication of the new research, Bryan said, is that there are differences between civilians as represented by the undergraduates and those in the military.
"A lot of the research is in non-military populations. A lot of the knowledge we have we glean from that research. We can't always assume that's correct."
For instance, the college students were much more likely to have attempted suicide if they were abused as children. For military members, assaults as adults were a bigger predictor of suicidal thoughts and attempts.
By one measure, the groups were similar: the more one has suffered abuse, the more likely he or she is to think about and attempt suicide.
Croft said he'd like to see more research into the effect of assault by fellow soldiers, as well as sexual assault of male military members.
Bryan said research now underway, involving student veterans, aims to assess the effect of assault when the perpetrator is a fellow military member. "We're hoping to study that more," he said.