An insight into light as a chronobiological therapy in affective disorders

Abstract

The field of chronobiology has vastly expanded over past few decades, bringing together research from fields of circadian rhythms and sleep. The importance of environmental day–night cycle on our health is becoming increasingly evident as we evolve into a 24-hour society. Reducing or changing sleep times against our natural instincts to rest at night has a detrimental impact on our well-being. The mammalian circadian clock, termed the suprachiasmatic nucleus, is responsible for synchronizing our behavioral and physiological outputs to environment. It utilizes light transcoded by specialized retinal photoreceptors as its cue to set internal rhythms to be in phase with light–dark cycle. Misalignment of these outputs results in symptoms such as altered/disturbed sleep patterns, changes in mood, and physical and mental exhaustion – symptoms shared by many affective clinical disorders. Key links to circadian abnormalities have been found in a number of disorders, such as seasonal affective disorder, nonseasonal depression, and bipolar affective disorder. Furthermore, therapies developed through chronobiological research have been shown to be beneficial in treatment of these conditions. In this article, we discuss impact of circadian research on management of affective disorders, giving evidence of how a misaligned circadian system may be a contributor to symptoms of depression and how moderating circadian rhythms with light therapy benefits patients.