Adult depression is typified by prolonged episodes of sadness and inability to experience pleasure. There are different types of depression with a variety of causes as well as physical, cognitive, and affective symptoms. Physical symptoms include disturbances in activity, sleep, and eating patterns. Affective and cognitive symptoms include passivity, confusion, pessimism, helplessness, worthlessness, self-blame, and guilt. There are also different models of depression that tend to emphasize specific symptoms. The biological models, for example, focus on vegetative signs, biochemical changes, and brain-behavior pathways that are involved in depression. The cognitive and psychodynamic theories are based on reasoning, beliefs, and mood.

Reformulated attribution theory (Abramson, Seligman, & Teasdale, 1978) characterizes depression as having internal, stable, and global self-attributions of responsibility for negative events. Depressed individuals feel powerless yet responsible for events that go wrong, and their guilt is exaggerated. As Freud described it, depression is a disorder characterized by dissatisfaction with the ego on moral grounds. The guilt, shame, and self-derision that commonly accompany depression are viewed in biological models as correlates or outcomes of depression. In attribution theories, these qualities of individuals are viewed as proximal antecedents of depression. Traditional and reformulated psychodynamic theories view guilt, shame, and self-derision as both distal antecedents and central elements of the disorder.