Individual differences in taste, body weight, and depression in the "helplessness" rat model and in humans.

The helplessness paradigm is used extensively in basic stress research and is an experimental model of clinical depression. In Experiment 1, exposure to unsignaled, inescapable shock resulted in finickiness about drinking a weak quinine solution, as previously reported. In contrast, exposure to escapable shock resulted in marked individual differences in finickiness that were predicted by prestress body weight. A more sensitive index of finickiness was used in Experiment 2, and a correlation between body weight and finickiness was observed in nonshocked rats. In Experiment 3, measures of quinine reactivity and body weight predicted depressive symptomatology in a nonclinical human sample. Although research in the helplessness paradigm usually focuses on environmental determinants of distress, the paradigm may help identify and explain individual differences in, or intrinsic modulation of, stress and depression.