Stressor controllability, anxiety, and serotonin

it is argued that exposure to stressors can sensitize the neural machiner that mediates fear for a period of time, and that during this time period fear conditioning is potentiated and responses to ambiguous or mildly fearful stimuli are exaggerated. The controllability of the stressor is a key characteristic of the stressor which determines whether this sensitization occurs. That is, sensitization follows exposure to uncontrollable, but not to controllable, stressors. It is argued that this sensitization of the neural structures that mediate fear may be similar to what is meant by anxiety, and that brain serotonin systems are a key component of this sensitization process. The implications of this point of view for a variety of phenomena including learned helplessness and reactivity to drugs of abuse are discussed.