Veterans may be more likely to commit suicide during the first year after they leave the military than after more time passes, a U.S. study suggests.

Compared with people still on active duty in the military, veterans out of the service for up to three months were 2.5 times more likely to commit suicide, the study found. Veterans who had left the service from three to 12 months earlier had almost triple the suicide odds of current members of the military.

"Family members and community can be proactive to reach out to veterans if they recently experienced stressful events - not just limited to the stressful events we can capture in the data such as divorce or separation from the military," said lead study author Yu-Chu Shen, a researcher at the Naval Postgraduate School in Monterey, California.

"In addition, clinicians should be aware that deployments may increase suicide risk independently of underlying mental disorders, and so asking patients about deployment history is advisable," Shen said by email.

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To assess how different types of experiences during military service and afterwards might influence suicide risk, researchers analyzed data collected on almost 3.8 million current and former service members from 2001 to 2011.

Overall, there were 4,492 suicides in the study population.

The strongest predictors of suicide were current or past diagnoses of self-inflicted injuries, major depression, bipolar disorder, substance abuse or other mental health conditions, researchers report in The Lancet Psychiatry.

Compared with service members who were never deployed, those who were currently deployed had a 50 percent lower risk of suicide, the study found.

However, in the first quarter following deployment, service members had a 50 percent higher risk of suicide than their peers who didn't experience deployment.

The study didn't examine why the suicide risk was lower during deployment than afterwards. But it's possible service members benefited from the positive psychological impact of belonging to a group with a shared mission during deployment, Shen said, then had more time to contemplate any negative feelings about their experiences when they were no longer on the mission.

When they left the military, the risk of suicide remained higher than for current service members for several years. Six years after leaving the military, veterans had a 63 percent higher risk of suicide than those still in the service, the study found.

One limitation of the study is that researchers lacked data on mental health disorders diagnosed after separation from the military, the authors note. They also lacked data on civilian experiences like divorce, unemployment, financial hardship or housing insecurity that could all influence mental health and the risk of suicide, the researchers point out.

The study also doesn't account for the frequency or intensity of combat experiences, noted Dr. Charles Hoge, a senior scientist at the Walter Reed Army Institute of Research who wrote an accompanying editorial.

Still, the findings suggest that veterans may need mental health services long after they return home.

"Unfortunately, despite numerous efforts to reduce stigma and other barriers to care, stigma remains pervasive in society and many veterans still do not seek help when needed," Hoge told Reuters Health by email.

"There are a number of warning signs for underlying mental health problems that may require treatment, such as withdrawal from family and friends, noticeable changes in functioning or behavior, talking about suicide or death, giving away belongings, increasing alcohol or substance use, or expressions of hopelessness or worthlessness," Hoge added.

One immediate resource that is available 24/7 is the national suicide prevention lifeline 1-800-273-8255.