Stress, aggression, and the balance of approach and avoidance.

Stress is a well-established risk factor for many mental disorders including anxiety disorders or substance abuse. A hallmark of these disorders is an imbalance between behavioral approach and avoidance in situations with approach-avoidance conflicts and unclear outcomes. However, if and how stress affects human behavior in approach-avoidance conflicts is largely unknown. To investigate the effects of stress on approach-avoidance behavior, 80 participants underwent a stress or control manipulation before performing an approach-avoidance conflict task. Stress markedly increased behavioral inhibition when threats were distant and accelerated responses when threats were close; suggesting that stress amplifies the importance of threat distance. However, participants high in trait aggression showed increased approach behavior, particularly when stressed. These findings indicate that stress generally leads to enhanced avoidance, but induces approach in individuals prone to aggression, with important implications for stress-related psychopathologies.