Behavioral Sensitization Demonstrated in People

Behavioral sensitization, a phenomenon involving escalating behavioral responses to repeated exposure to a stimulus such as a drug or possibly psychosocial stress, is thought to contribute to the refractory course of progressive psychiatric syndromes (i.e., increasingly severe recurrences of bipolar mood disorders in response to less provocation, or recurrences of PTSD symptoms triggered by less severe stress). However, with few exceptions, behavioral sensitization has been demonstrated only in animals. This controlled study indicates that behavioral sensitization occurs in humans as well.

Researchers administered d-amphetamine (0.25 mg/kg) to 11 normal volunteers on days 1 and 3 or 2 and 4 and placebo on alternate days. The subjects had no …