(LATIMES) — A tour of duty in Afghanistan or Iraq — even one involving combat — does not increase a service member’s risk of suicide, according to a study that tracked more than 150,000 troops for up to eight years.

The study, published Tuesday in the Journal of the American Medical Assn., challenges the common assumption that the stresses of being in a war zone and exposure to the horrors of battle are behind a sharp increase in the military’s suicide rate over the last decade.

“People have said, ‘Of course it’s multiple deployments, it’s the length of deployments, it’s combat. That’s a no-brainer,'” said Matthew Nock, a Harvard University psychologist and suicide expert who was not involved in the study. “But that appears not to be the case.”

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