WASHINGTON (CBS DC) — Nearly one-in-five U.S. soldiers had suffered from a mental illness before enlisting in the Army, and about one-in-ten soldiers had thought about killing themselves prior to enlistment.

A new study published Monday in JAMA Psychiatry finds that most mental health disorders and suicidal tendencies among U.S. Army soldiers started before their military enlistment. The findings raise questions about the screening of military recruits, and analyzed a high-risk combination of mental health problems, the stresses of deployment and the increased likelihood of acting on prior suicidal thoughts among U.S. soldiers.

In the largest-ever, multi-part study of mental health risk from the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS), researchers found that a majority (58.2 percent) of soldiers who ever thought of suicide had considered the idea before enlistment. The initial findings analyzed the prevalence of mental disorders among service members in comparison to civilians, and provide a multi-dimensional analysis of how the increased demands of deployment have affected the suicide rate.

The annual soldier suicide rate between 2004 and 2009 more than doubled to over 23 per 100,000. In that time period, 569 soldier deaths were found to be suicides.

Over three-quarters (76.6 percent) of soldiers with current mental disorders had onsets prior to enlistment.

“Some of the differences in disorder rates are truly remarkable,” said Ronald Kessler, McNeil Family Professor of Health Care Policy at Harvard Medical School and senior author of the paper on mental disorder prevalence. “The rate of major depression is five times as high among soldiers as civilians, intermittent explosive disorder six times as high, and PTSD nearly 15 times as high.”

Nearly 60 percent of solider suicide attempts were traced to pre-enlistment mental disorders, which are acutely more common among non-deployed U.S. Army soldiers than demographically similar portions of the general population, according to the study.

About one-in-ten soldiers qualified for a diagnosis of “intermittent explosive disorder,” a psychiatry diagnosis five times higher than that of the general population.

The three-part study analyzed data from confidential surveys and interviews with 5,428 soldiers at Army bases around the country, and in some respects, the findings on suicide were similar to that of the civilian population. The second of the three Army STARRS papers found that 13.9 percent of soldiers considered suicide at some point in their lifetime, and 2.4 percent had attempted suicide – a rate that is actually twice as high for civilians, although soldiers’ suicide attempts are more commonly lethal.

Between 47-60 percent of suicide considerations or action first occurred prior to enlistment.

“It is striking that nearly 50 percent of the soldiers who attempted suicide made their first attempt before joining the Army, as history of suicide attempts is asked about in recruitment interviews and applicants who report such a history typically are excluded from service,” Matthew Nock, professor of psychology at Harvard University and lead author of this report on soldier suicides, said in a statement.

About one-quarter of the soldiers qualified for at least one current, common psychiatric disorder, including depression, anxiety or substance abuse.

Nock noted that Army outreach and intervention programs for new soldiers may be the most practical implication of the research.

“The people at highest risk of making an attempt struggled with depression and anxiety, or post-traumatic stress, in combination with impulsiveness and aggression,” Nock told The New York Times. “The former gets people thinking about suicide, and the latter gets them to act on those thoughts.”