Chronobiological Treatments

Chronobiology is the study of circadian rhythms that are present in many aspects of our daily health, from molecular to behavioral levels. Bright environmental light is known to synchronize the biological clock in the brain that regulates circadian hormonal and sleep–wake cycles. There is increasing evidence for disruption of circadian rhythms in the pathophysiology of major depressive disorder (MDD), especially in seasonal affective disorder (SAD). Chronobiological treatments that target the circadian system, including wake therapy (total sleep deprivation) and light therapy, have been studied for over four decades, with evidence supporting their efficacy in SAD and non-seasonal MDD, as well as in other psychiatric conditions. Wake and light therapies are useful additions to the clinical armamentarium for patients with MDD because of their noninvasive nature, low propensity for adverse events, rapid onset of effect, low cost, and ease of combining with other treatments for depression.