Anhedonia: a neglected symptom of psychopathology.

In the last century psychopathologists attached importance to the concept of anhedonia, the loss of ability to experience pleasure. Its role in the diagnosis of melancholia was considered to be crucial. In the present century attention to anhedonia has faded, possibly because of the focus upon depressed mood as the pathognomonic feature of depressive disorders. Research on the symptomatology of endogenous depression did not include the concept; anhedonia was also lacking from the major instruments of psychiatric research, the depression rating scales, Attention was drawn to anhedonia by two authors: by Meehl in the 1960s and by Klein in the 1970s. Meehl considered anhedonia from the point of view of a personality defect predisposing to mental illness; and Klein regarded anhedonia to be a symptom of depressive illness and probably the best clinical marker predicting response to antidepressant drugs. In 1980 the revised DSM presented the concept of 'loss of interest or pleasure' as one of the two cardinal symptoms of major depression. Since then there has been a gradual recovery of emphasis although many systems confuse the two concepts of 'loss of interest' and anhedonia. It is possible that anhedonia may provide the key to a more exact delineation of depressive disorders in biological research and in clinical practice. Further research will depend upon a more precise, cross-nationally agreed definition of the concept and the means of its assessment.