THE CIRCADIAN SYSTEM AND THE THERAPEUTICS OF THE AFFECTIVE-DISORDERS

Establishing that a circadian rhythm is abnormal tells us little about the cause, which can arise from changes in the patient's lifestyle, i rregularities of the body clock or a malfunction in the process of ent rainment of the clock. In a clinical context, such a range of possible explanations implies differences in the most appropriate mode of trea tment. Against this background, the conventional view that the underly ing abnormality in endogenous depression is due to a disorder of the b ody clock is challenged. The challenge is based on difficulties of int erpretation of the clinical data and the results of studies on circadi an rhythms in patients. It is suggested that the state of the circadia n system in depression resembles its state in healthy individuals afte r time-zone transitions or in shift work maladaptation syndrome and th at this disturbance should be seen as resulting from changes in the ph asing of external zeitgebers rather than from an abnormality in the cl ock itself.