Impact of behavioral inhibitory control and startle reactivity to uncertain threat on youth suicide risk

Poor inhibitory control and exaggerated threat reactivity are two well-established risk factors for suicide. Theory suggests that these two factors may interact to influence suicide risk, although few studies have directly tested these relationships. In the present study, we examined the unique and interactive effects of inhibitory control (IC) and threat reactivity on self-reported suicide risk in a sample of 132 youth, ages 16-19. The stop signal task was used as a behavioral index of IC. Threat reactivity was captured using a modified version of the No-Predictable-Unpredictable threat paradigm that includes threat of predictable (P-) and unpredictable (U-) mild electrical shock. Startle eyeblink potentiation was measured throughout the task as an index of aversive responding. All participants completed a battery of well-validated self-report measures including current suicide risk. Hierarchical linear regression analyses controlling for age and sex revealed no main effects of IC or threat reactivity. However, there was a significant IC by reactivity to uncertain threat (U-threat) interaction. At lower levels of IC, greater startle reactivity to U-threat was associated with greater suicide risk. At higher levels of IC, there was no association between reactivity to U-threat and suicide risk. These results suggest that individual differences in IC and reactivity to U-threat interact to influence suicide cognitions, shedding light on potential subgroups of individuals who might be at elevated risk.