Socially explosive minds: The triple imbalance hypothesis of reactive aggression

ABSTRACT The psychobiological basis of reactive aggression, a con-dition characterized by uncontrolled outbursts of socially violent behav-ior, is unclear. Nonetheless, several theoretical models have been proposed that may have complementary views about the psychobiolog-ical mechanisms involved. In this review, we attempt to unite these models and theorize further on the basis of recent data from psychological and neuroscientific research to propose a comprehensive neuro-evolutionary framework: The Triple Imbalance Hypothesis (TIH) of reactive aggres-sion. According to this model, reactive aggression is essentially subcor-tically motivated by an imbalance in the levels of the steroid hormones cortisol and testosterone (Subcortical Imbalance Hypothesis). This im-balance not only sets a primal predisposition for social aggression, but also down-regulates cortical–subcortical communication (Cortical-Sub-cortical Imbalance Hypothesis), hence diminishing control by cortical re-gions that regulate socially aggressive inclinations. However, these bottom-up hormonally mediated imbalances can drive both instrumen-tal and reactive social aggression. The TIH suggests that reactive aggres-sion is differentiated from proactive aggression by low brain serotonergi