Circadian Rhythm Disturbances in Affective Disorders: Facts and Fictions

The cycling nature of affective disorders has put these psychopathological conditions into the focus of medical chronobiology. However, our knowledge is still rather limited in this respect, and too often casual observations and theoretical speculations are accepted as proving profound disturbances of biological (above all, circadian) rhythms in these disorders. It is our intention to evaluate critically the present state of knowledge in this field in order to disentangle proved facts from mere fictions. Particular reference is made to carefully designed observations of affectively ill patients in a time-cue-free environment, as they provide the only solid basis for conclusions regarding the endogenous component of biological rhythms. Only those hypotheses are discussed that have drawn most attention in chronobiological research to affective disorders.