Abstract
Biological rhythm disturbances have been implicated in the development of some mood disorders. Thouh much recent interest has been focusefi on seasonal affective disorder, patients with nonseasonal depression also show evidence in many cases of disturbed circadian rhythms. Typically the biologic rhythm disturbances seen in both disorders resolve as symptoms abate, thus suggesting a potential therapeutic role for interventions that manipulate daily rhythms (such as light exposure).
This paper reviews the concept of biological rhythms and the relationship of these rhythms to environmental modulators (particularly light). The connection between disturbed circadian rhthms and the smptomatic expression of goth seasonar and nonseasonal depression is discussed, and studies on the efficacy of environmental manipulations, particularly light therapy, are reviewed anf contrasted with those responses predicted by circadian theories.