Deployed military service members who experience certain types of combat events or are exposed to high levels of combat may be at a higher risk of suicide attempt, researchers found in a study published in JAMA Network Open. They analyzed linked medical encounter data and data from the Millennium Cohort Study, an ongoing prospective longitudinal study of members of all US military branches.

The researchers collected data from 57,841 active-duty service members (44,062 men and 13,779 women) from the first 4 enrollment phases of the Millennium Cohort Study who had deployed in Iraq and Afghanistan. They excluded individuals who had a suicide attempt before first deployment.

Participants quantified their combat experience and self-reported overall combat severity and exposure to certain combat experiences: feeling in great danger of being killed, being attacked or ambushed, receiving small arms fire, clearing/searching homes or buildings, having an improvised explosive device (IED) or booby trap explode near them, being wounded or injured, seeing dead bodies or human remains, handling or uncovering human remains, being directly responsible for the death of an enemy combatant or noncombatant, and knowing someone, seeing Americans, or having a member of their unit seriously injured or killed.


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Overall, experiencing combat and high combat severity were significantly associated with suicide attempts (P <.05), but combat, defined broadly, was not associated with suicide attempts after adjustments for demographic and military-specific factors.

After adjusting for those factors and accounting for mental health at enrollment, the researchers found that being attacked or ambushed (hazard ratio (HR), 1.55; 95% CI, 1.16-2.06), seeing dead bodies or human remains (HR, 1.34; 95% CI, 1.01-1.78), and being directly responsible for the death of a noncombatant (HR, 1.81; 95% CI, 1.04-3.16) were significantly associated with suicide attempt.

Models stratified by mental health status (neither, post-traumatic stress disorder [PTSD] only, depression only, or comorbid PTSD and depression) indicated that among those with depression only, being directly responsible for the death of an enemy combatant was significantly associated with an increased risk of suicide attempts (adjusted HR, 5.85; 95% CI, 2.26-15.17).

In the mediation analyses, the researchers found that high combat exposure was associated with PTSD only (β=2.07; P <.001) and comorbid PTSD and depression (β=2.01; P <.001), which, in turn, were associated with suicide attempts (β =0.66; P =.003 for PTSD only, and β= 0.72; P <.001 for comorbid PTSD and depression).

This study was limited by the fact that it relied on ICD-9 codes to identify suicide attempts, which have led to underestimating suicide attempts and limiting statistical power.

“Clinicians should be aware of the importance of inquiring about the nature of combat experiences, paying particular attention to experiences that may involve unexpected events, more passive events that may be associated with feelings of helplessness, or events that are more challenging from a moral or an ethical perspective,” the investigators said.

Disclosure: An author associated with this study declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

LeardMann CA, Matsuno RK, Boyko EJ, Powell TM, Reger MA, Hoge CW; Millennium Cohort Study. Association of combat experiences with suicide attempts among active-duty US service members. JAMA Netw Open. 2021;4(2):e2036065. doi:10.1001/jamanetworkopen.2020.36065