The risk of attempted suicide peaks at several points during enlisted soldiers' time in the U.S. Army, a new study found.

Soldiers who were never deployed were at highest risk for suicide attempts during their second month of service.

Risk among soldiers on their first deployment was highest during the sixth month of deployment.

And among those who'd completed deployment, risk peaked again five months after they'd returned home, researchers found.

"Suicide attempts are important targets for care," said lead author Dr. Robert Ursano, of the Uniformed Services University of the Health Sciences in Bethesda, Maryland. "We always talk about completed suicide, but completed suicide is just the tip of the iceberg."

He and his colleagues write in JAMA Psychiatry that suicide attempts have increased in the U.S. Army over the past decade but haven't been closely studied.

Understanding risk factors helps in the creation of interventions for suicide attempts, the researchers add.

Their new report focused on 163,178 enlisted Army soldiers on active duty between 2004 and 2009. During that time, 9,650 soldiers attempted suicide. About 86 percent were male, about 68 percent were younger than 30, and most were white, high school graduates and married.

While 40 percent of the total population had never been deployed, that group accounted for about 61 percent of the soldiers who attempted suicide. Previously deployed soldiers accounted for 29 percent of the suicide attempts, and currently deployed soldiers accounted for about 10 percent.

Regardless of deployment status, risk of suicide attempts was higher among female soldiers, early-career soldiers and those with a recent mental health diagnosis. Deployment status was also tied to suicide attempt risk.

Among soldiers with just one previous deployment, odds of a suicide attempt were higher for those with depression or post-traumatic stress disorder.

The new study can't say why risk of suicide attempt peaks at different times during different phases, but Ursano pointed out that the variations were seen in people of different skill levels in different environments.

"It’s important to remember both the people and stressors are changing," he said.

The new research is a part of the Army Study to Assess Risk and Resilience in Servicemembers (Army STARRS). According to Ursano, Army STARRS is modeled after the famed Framingham Heart Study, which started tracking participants in 1948 and formed the basis for recommendations to maintain a healthy heart.

"Suicide attempts are very important to think about," Ursano told Reuters Health. "In the U.S. there are more suicide attempts each year than there are first heart attacks. So suicide and suicide attempts are important to target with interventions."