"It's not true that repeated deployments are the primary factor involved in the suicide issue," Robert Ursano of the Uniformed Services University in Maryland told reporters.
"There's no question that repeated deployments increase stress on individuals, and increase stress on families and stress on the community. But it's a much more complicated picture," said Ursano, who is the director of a major new study looking at mental health and suicide in the US Army's ranks.
About a third of those who commit suicide in the army have not even deployed for combat duty in Iraq or Afghanistan, US Army Secretary Pete Geren said at the same press conference.
Another third kill themselves while deployed and the remaining third have deployed at some point, Geren said.
The military has become increasingly concerned over a steady rise in suicides for two years running, and top officers have cited repeated combat tours as a likely factor.
Last year 128 soldiers took their lives, up from 115 in 2007.
The number of suspected suicides in the first half of 2009 reached 88, compared to 67 for the same period last year, according to recently released figures.
For years, the suicide rate in the military was lower than among the wider civilian population. But that pattern changed in 2008.
The suicide rate last year among active duty soldiers rose to 20.2 per 100,000, surpassing a demographically adjusted national suicide rate of 19.5 per 100,000 in 2005, the latest year on record.
General Peter Chiarelli, Army vice chief of staff, said the number of suicides had dropped somewhat in the past four and a half months but it was too early to tell if the trend would continue.
"We feel better about our efforts in the last four and a half months to at least reduce the number. And we hope we will continue to do that with some of our intervention programs," the general said.
He said the Army was still searching for the most effective methods to counter suicide and had commissioned the largest study of suicide and mental health ever conducted in the military to get at the roots of the problem.
The study will look at an array of factors possibly associated with suicide, including combat-related trauma, personal and economic stress, family history, childhood abuse, a military unit's cohesion and general mental health.
The 50-million-dollar study will include a survey of the up to 120,000 recruits who enter the Army every year, according to the National Institute of Mental Health (NIMH), which is carrying out the research.
The study also will survey about 90,000 active-duty Army personnel and take saliva and blood samples for genetic and neurobiological studies.
The research team will analyze data and interview soldiers who attempted suicide in the past and compare them to individuals with similar demographic details.
Although the elaborate study will last for five years, it is designed to quickly identify key "risk factors" that could lead to suicide and the most effective methods to prevent soldiers from taking their own life, said NIMH director Thomas Insel.