Adapted to fear: Fearlessness about death is associated with heart rate variability

Objective: Capability for suicide, which refers to an individual’s ability to enact potentially lethal harm to oneself and overcome the fear of dying, is an empirically supported component of the Interpersonal-Psychological Theory of Suicide. Although an abundance of research has examined capability for suicide through the use of self-report data, little research has assessed specific psychophysiological mechanisms that may contribute to capability for suicide. We assessed relationships between capability for suicide (fearlessness about death and pain tolerance), high frequency heart rate variability (HF HRV), and subjectively reported fear during a death related event. Given that greater HRV is associated with calmness and lack of distress, we predicted that HRV during a fearful event would be positively associated with the capability for suicide. Method: Data were collected from 101 undergraduates. Participants self-reported fearlessness about death and had their pain tolerance assessed with an algometer. HF HRV was assessed prior to, during, and following a film-viewing task designed to elicit fear of death. Results: Correlations revealed that fearlessness about death was negatively associated with self-reported fear during the film viewing and positively associated with self-reported and objective pain tolerance. Linear regressions found that fearlessness about death, but not self-reported or objective pain tolerance, was positively associated with HF HRV during the film-viewing and recovery. Discussion: During a fearful, death related event, greater HF HRV was associated with greater fearlessness about death, suggesting that HF HRV may represent one possible mechanism through which fearlessness about death is maintained