The soldiers will be asked on a volunteer basis for personal information that can be used to make psychological assessments. Family members might be contacted for further information. In some cases, saliva and blood samples will be collected for genetic and neurobiological studies.
The information will serve as an "ongoing natural laboratory," officials said, as researchers follow these soldiers for years, looking for common strands as to which individuals are more likely to commit suicide.
"We're looking at suicide as the culmination of a long chain of events," said Robert K. Heinssen, the NIMH study director.
In 2008, 143 soldiers committed suicide, the highest number in the three decades that the Army has kept records.
"The most frustrating thing is trying to find a cause," Gen. Peter W. Chiarelli, the Army's vice chief of staff, told the Senate Armed Services Committee on July 30.
The five-year, $50 million study, which stems from an agreement in October between the Army and NIMH, is an ambitious attempt to solve the mystery.
Last month, Robert J. Ursano, chairman of the psychiatry department at Uniformed Services University of the Health Sciences in Bethesda, was named to lead an interdisciplinary team of four research institutions involved in the project.
The study will be "complex in its design, and it's looking at a rare phenomenon," Ursano said.
A number of factors may play roles in suicide, according to Ursano, including post-traumatic stress disorder, family issues, alcohol abuse and neurobiological factors.
Repeated deployment to Iraq, Afghanistan and elsewhere since 2001 is another factor, but one that does not by itself account for the increases in suicide, Ursano said.
"It's a much more complex aggregate of factors," Ursano said. "Deployment increases the stress on a family, but it's clearly not the deciding factor."
The surveys are expected to begin early next year. The information gathered on individual soldiers will be subject to strict privacy safeguards, officials said.
In addition to the planned surveys, researchers are working with the Army to identify and collect relevant information from existing databases, Heinssen said. Data on soldiers who have committed suicide since 2004 will be analyzed.
While the study will continue for years, the researchers are expected to quickly identify and report on potential risk factors to help the Army prevent suicide.
"That's kind of a different way of doing business for us," Heinssen said.
NIMH will report to the Army on a quarterly basis beginning in November. Findings will be incorporated as quickly as possible into treatment programs, according to Chiarelli.