Deployment to Iraq or Afghanistan increases the risk for death by suicide among current and former US military personnel, new research shows.

"Most population-based studies [of suicide] have not included a complete set of previous mental health histories, and they claimed there is no association between deployment and suicide death," Yu-Chu Shen, PhD, professor of economics, Naval Postgraduate School, Monterey, California, told Medscape Medical News.

"But the risk of suicide death is quite different between the time service members are deployed and once they return [and leave the military], so essentially, once you are deployed, the risk remains similar whether you are deployed multiple times.... It's really exposure to deployment that changes the risk of suicide death," she added.

"So for clinicians who are seeing service members, the first thing they need to know is: When was the last time you were deployed? That should be part of their clinical observation," Dr Shen advised.

The study was published online September 30 in the Lancet Psychiatry.

Large Scale Study

The investigators conducted a retrospective analysis of 3,795,823 US military personnel between 2001 and 2011. The study population was followed to the time of death or December 31, 2011, irrespective of whether the individual left the military.

Deaths by suicide were counted if they occurred either during active duty, while individuals were in the reserves, or once they had left the military.

Mental health diagnoses were obtained from medical records for the period during which service members were on active duty. Quarterly personnel data were obtained from military databases for each individual's years of service.

"Between 2001 and 2011, we noted 4492 suicides [that] occurred in our analysis population," said Dr Shen.

Time-varying predictors were then applied to personnel involved in either Operation Iraqi Freedom or Operation Enduring Freedom, in Afghanistan.

The risk for death by suicide was 50% lower among personnel who were actively engaged in military service during the first quarter of deployment compared with individuals who had never been deployed.

This makes intuitive sense in that, once deployed, service members become part of a cohesive unit.

"There's also a lot of peer support during deployment, but once service members return, their risk of suicide goes up," said Dr Shen.

Indeed, on their return, the risk for suicide in the current cohort increased by more than 50% if the individual had been deployed in the previous 3 quarters, and this elevated risk only dissipated some 16 quarters after an individual had left active service.

"By far the strongest predictors [of suicide risk] were diagnoses of self-inflected injury," the investigators write.

For example, during the quarter in which an individual was diagnosed with a self-inflicted injury, the risk for death by suicide was 8.34 times higher than it was for military personnel with no such history, and the risk remained significantly higher in all subsequent quarters, she noted.

"Current and past diagnoses of all other mental health diagnoses — except posttraumatic stress disorder — were also strongly associated with an increased risk of death by suicide," said Dr Shen.

Table. Hazard Ratios for Death by Suicide and Mental Health Disorders

Fully Adjusted HR P Value Major depression (vs never diagnosed) 1.00 Diagnosed during the current quarter 2.10 <.0001 Diagnosed in the previous 3 quarters 1.76 <.0001 Bipolar disorder (vs never diagnosed) 1.00 Diagnosed during the current quarter 2.44 <.001 Diagnosed in the previous 3 quarters 2.08 <.0001 Anxiety disorder (vs never diagnosed) 1.00 Diagnosed during the current quarter 1.46 .103 Diagnosed in the previous 3 quarters 1.34 .043 Other mental health diagnoses (vs never diagnosed) 1.00 Diagnosed during the current quarter 2.34 <.0001 Diagnosed in the previous 3 quarters 3.43 <.0001

The risk for suicide was also elevated for individuals who had violated the law, as reflected by their having received an "enlistment entry waiver" for either a drug-related or non-drug-related offence.

"For example, relative to having no enlistment waiver, a waiver for a major, non-drug-related offence was associated with a 53% raised hazard rate of death by suicide," Dr Shen and colleagues write.

Stressful life events such as divorce and demotion in rank also significantly increased the likelihood of an individual committing suicide, as did leaving military service, especially during the first year of separation.

Additionally, investigators showed that the risk for suicide was 12 times higher among those who had only served 6 months before separating from the military, the authors note.

Upward Trend

In an accompanying editorial, Charles Hoge, MD, Walter Reed Army Institute of Research, Silver Spring, Maryland, Christopher Ivany, MD, Office of the Army Surgeon General, Falls Church, Virginia, and Michael Schoenbaum, PhD, Research National Institute of Mental Health, Bethesda, Maryland, point out that the upward trend in suicide among US military personnel coincides with 15 years of operations in Iraq and Afghanistan.

"Between 2005 and 2009, the incidence of suicide nearly doubled in both deployed and nondeployed US Army and Marine personnel, matching or slightly surpassing civilian rates, and has remained high since," they write.

The increase in suicide rates during this time occurred only among service members in the Army and the Marines, they add.

In contrast, suicide rates among US Navy and Air Force personnel have remained below civilian norms, they note.

Speculating as to what may be driving these trends, the editorialists suggest that personnel in the Army and the Marines were most likely to be deployed to Iraq and Afghanistan, where they "endured frequent lengthy rotations, comparatively short dwell time between deployments, and intense training schedules when not deployed that took substantial additional time away from home."

Faced with the need to constantly prepare for deployment may have negatively shaped Army and Navy forces for years, a suggestion that appears to be supported by rising rates not only of suicide among the deployed and nondeployed but also in the prevalence of mental disorders.

"The increase in suicides in Army and Marine personnel has certainly been taken very seriously, including multiple efforts to reduce stigma, enhanced treatment, and conducting research such as the Shen et al article," Dr Hoge told Medscape Medical News.

"For all providers, it is important to ask about military service and whether the patient continues to struggle with war-related or trauma-related health concerns, which may include physical, cognitive, or psychological symptoms, and then follow up as indicated," he said.

Dr Hoge added that it is also important to routinely screen for depression in primary care, using a tool such as the nine-item Patient Health Questionnaire depression measure, with follow-up evaluation and referral as clinically indicated.

Screening for alcohol or substance misuse is another important domain that is often neglected.

"Since mental disorders are the strongest modifiable predictors for suicide, interventions to foster greater engagement in care and reduce treatment dropouts (especially during periods of transition) remain high priorities," the editorialists conclude.

The authors and editorialists have disclosed no relevant financial relationships.

Lancet Psychiatry. Published online September 30, 2016. Abstract, Editorial