Suicidal Behavior in Depression: A Severe Form of Depression or a Distinct Psychobiology?

Abstract

Although depression is one of the strongest risk factors of suicidal behavior, only a small fraction of people with depression engage in suicidal behaviors. Suicidal behavior in depression may be more than just a severe form of depression, and distinct predispositions to suicidal behaviors in depression should be better understood. We reviewed previous research findings about suicidal disposition among depressive patients. Interplay between interconnected neural systems contributes to suicidal behaviors in depression, and these neurobiological changes underlie the psychological vulnerability of suicidal behavior. Hopelessness and pessimism predict future suicide attempt and completion among depressive patients. The depletion of noradrenaline may underlie this hopelessness. Impulsive and aggressive behaviors have been identified as key predictors of repetitive suicide attempts. Impulsive and aggressive traits of suicidal patients may be linked with the hypofunction of their serotonin system. These two traits may also be associated with comorbidities with borderline personality disorder that increase suicide risk. Cognitive rigidity may also increase the risk of suicidal behavior, by inhibiting effective coping with stressors and heightening hopeless and pessimistic thinking as the outcome. This impairment in executive functioning may result from dysfunction of the prefrontal cortex, perhaps associated with the alterations in serotonergic and adrenergic systems. Depressive patients with the aforementioned predispositions may be highly vulnerable to suicide risk. Therefore, the assessment and treatment for suicidal behaviors in depressive patients should carefully consider these predispositions. Reconceptualization of suicidal behavior as a distinct disorder may improve suicide risk screening and detection in clinical practice and also help expand suicide research by using a well-defined phenotype.