The sleep-wake cycle occurs because of the two independent but additive processes, homeostatic sleep and circadian processes. Circadian rhythms play a significant role in regulating daily behavioral rhythms, cortisol and melatonin secretions, body temperature, sleep/wake cycle, alertness and performance levels. Disrupted synchronization of circadian rhythms impairs cognition, behavior and mood with deterioration of sleep-wake cycle and social rhythms. Some clinical and neurobiological findings suggest circadian dysregulation in depressive patients. Diurnal variation of mood, early morning awakening, phase advance for body temperature, cortisol, latency of the first phase of REM sleep for several other hormones and monoamines or their metabolites and sleep disturbances are core features of depression that have linked depression with circadian rhythm function (1,2).
Clinical and neurobiological findings have promoted the idea that the restoration of circadian rhythm could have an antidepressant effect. The term, chronotherapeutics, refers to biologically-based, non-pharmaceutical and clinical interventions that act on disrupted biological rhythms in order to achieve therapeutic effects in the treatment of psychiatric conditions (3). Delayed therapeutic effects, tolerability, side effects, and drug–drug interactions of pharmacotherapeutic agents, as well as pregnancy and the postpartum period, prevent antidepressant use and promote chronotherapeutic interventions.
Chronotherapeutics are applied effectively in endogenous, reactive, unipolar, bipolar, schizoaffective depression, depression in the elderly, secondary depression, depression in pregnancy and postpartum depression. The target of chronotherapeutic interventions, as in antidepressant drug treatments, is to modulate the same neurotransmitter systems (5-HT, NA, DA), the same brain structures, and the same clinical symptoms and findings more rapidly and with fewer side effects. These interventions include wake therapy (the use of prolonged periods of wakefulness; partial or total sleep deprivation), shifting of sleep time (sleep phase advance therapy; stepwise shift forward of the sleep-wake cycle to the early evening); bright light therapy in correct time and sufficient dose, and dark or rest therapy for bipolar mania and rapid cycling patients. When the therapeutic effects are transient, different chronotherapeutic interventions can be combined to maximize antidepressant response and prevent relapse. Psychiatrists should consider chronotherapeutic interventions as strong and safe treatment approaches (3,4).
References:
1. Lack LC, Wright HR. Chronobiology of sleep in humans. Cell Mol Life Sci. 2007; 64(10):1205-15.
2. Selvi Y, Besiroglu L, Aydin A. Chronobiology and Mood Disorders. Current Approaches in Psychiatry 2011; 3(3):368-386.
3. Benedetti F, Barbini B, Colombo C. Smeraldi E. Chronotherapeutics in a psychiatric ward. Sleep Med Rev. 2007;11(6):509-22.
4. Hajak G, Landgrebe M. Time and depression: when the internal clock does not work. Medicographia. 2010;32:146-151.