Neuropeptide Y plasma levels and suicidal behavior in combat veterans

War veterans are at increased risk of suicide that may be related to deployment and/or post-deployment stressors and to adjustment-related factors. The aim of this study was to examine whether levels of plasma neuropeptide Y (NPY) might distinguish combat veterans who have made a post-deployment suicide attempt from those who have never made a suicide attempt. We focused on NPY because of prior findings linking NPY with the neurobiology of resilience, stress-related and other disorders, and suicidal behavior. Demographic and clinical parameters of suicide attempters and non-attempters were assessed and plasma NPY was determined by radioimmunoassay. NPY levels were higher among attempters in comparison to non-attempters, controlling for sex and body-mass index. Suicide attempters had higher Scale for Suicidal Ideation (SSI) scores than non-attempters. There was a positive correlation between NPY levels and SSI scores among non-attempters but not among attempters. Likewise, NPY levels positively correlated with Brown-Goodwin Aggression Scale scores among suicide attempters but not among non-attempters. This is the first demonstration of altered plasma NPY levels in association with suicide attempt history and suicidal ideation in veterans. Our findings suggest that clinical differences between combat veterans with or without a history of suicide attempt may have a neurobiological origin.