The study in the Journal of the American Medical Association included over 150,000 current and former military personnel from all service branches.
An analysis of questionnaire data for 83 who killed themselves between 2001 and 2008 found that factors associated with increased risk of suicide included being male, having depression or manic-depressive disorder, engaging in heavy or binge drinking, and having alcohol-related problems.
However, they could find no link between increased suicide risk and combat experience, cumulative days deployed, or number of deployments.
The increased rate of suicide in the military "may largely be a product of an increased prevalence of mental disorders in this population," said the study led by Cynthia LeardMann of the Naval Health Research Center in San Diego, California.
The US military has noted an increase in suicides since 2005 that coincides with the deployment of soldiers in Iraq and Afghanistan, but the exact cause has been unclear.
The Pentagon's latest report on the matter said 301 service members died by suicide in 2011 -- up from 268 in 2008 -- and said that 64 percent of those who attempted suicide had a known history of a behavioral health disorder.
According to an accompanying JAMA editorial by Charles Engel, a doctor with the Uniformed Services University of the Health Sciences in Bethesda, Maryland, the new research offers hope for reducing the military suicide rate.
"These findings offer some potentially reassuring ways forward: the major modifiable mental health antecedents of military suicide - mood disorders and alcohol misuse - are mental disorders for which effective treatments exist," he wrote.