Review: Suicide and its relationship to aggression and impulsivity.

Aggression and impulsivity are key risk factors for suicide, which remains a public health concern. The heterogeneity of suicidal behaviors, combined with the complexities of aggression and impulsivity, complicates the investigation of their relationship with suicide risk. This review sought to provide a comprehensive overview of the literature examining the relationship between aggression, impulsivity, and suicide. Broadly, individuals with higher levels of aggression and impulsivity were found to be more vulnerable to suicidal behaviors. Stress, the immune system, and neurotransmitters also appeared to affect the relationship between aggression, impulsivity, and suicide. The reactive aggression and proactive aggression subtypes were each found to uniquely contribute to suicide risk. Furthermore, although different facets of impulsivity have varied relationships with suicide risk, self-reported impulsivity did not consistently align with task-driven impulsivity, and distinct facets of task-driven impulsivity demonstrated unique associations with suicide risk. Task-driven impulsivity and reward-based learning, as estimated by reinforcement learning hyperparameters, may provide valuable insights into the potential utility of tasks that assess risk factors in suicide research and their relationship with sensory and emotion regulation in the brain. In addition, neuroimaging studies indicated that decreased cognitive capability and control may be involved in the link between impulsivity and suicide. Collectively, the evidence presented herein highlights the complex interplay between aggression, impulsivity, and suicide. Understanding the underlying genetic, epigenetic, stress, neural, and neurotransmitter factors involved is crucial for developing effective prevention and intervention strategies for individuals at risk of suicide.