Abstract
Traumatic brain injury is associated with increased risk for suicide, but the underlying mechanisms remain poorly understood. One candidate mechanism is impulsivity, which includes both choice impulsivity (e.g., preference for smaller, immediate rewards) and motor impulsivity (inability to inhibit prepotent motor responding). We evaluated these facets of impulsivity in Veterans classified according to their history of mild TBI (mTBI) and/or prior suicide attempt. 99 Veterans were classified as having no mTBI or suicide attempt (control, n = 35), mTBI but no suicide attempt (mTBI, n = 42), or mTBI and prior attempt (mTBI+SA, n = 22). A computerized temporal discounting task (Monetary Choice Questionnaire) assessed choice impulsivity and a Go/No-go task assessed motor impulsivity. On temporal discounting, the control group showed less choice impulsivity than the mTBI group. Temporal discounting was not associated with suicide attempt history. However, among the mTBI+SA group, those with high-lethality suicide attempts showed less choice impulsivity than those with low-lethality attempts. No group differences emerged on the Go/No-go task. The findings are consistent with choice impulsivity as a potential pathway by which mTBI affects risk for suicide. The finding that high-lethality attempts were associated with greater willingness to wait for reward supports the emerging view of heterogeneous underlying pathways to suicide risk, with distinct phenotypes that implicate different therapeutic options.