events; or (b) serotonin function and substance use. One pathway (A in the figure, below) is associated with psychosocial crises and life events that can lead to depression, hopelessness, and suicidal ideation, thereby worsening impulse control. The other pathway (B) is associated with serotonin dysregulation (which can be influenced by substance use), that can also worsen impulse control. These pathways can operate independently or concurrently. Suicidal behaviors generally occur through two types of diatheses or vulnerabilities: 1) major psychopathology (most commonly depression); and 2) impulsive-aggression and its neurobiological correlates (impaired executive function, and serotonin dysregulation in the ventral prefrontal cortex) (Brent and Mann, 2003; Mann et al. 1999; Shaffer and Pfeffer, 2001).
