[Circadian rhythms and depression].

Depressive disorders are associated with various neurobiological alterations like hyperactivity of the hypothalamic-pituitary-adrenal axis, altered neuroplasticity and altered circadian rhythms. Relating to the circadian symptoms, a process is adopted in which individual genetic factors together with social, psychological and physical stressors may lead to a decompensation of the circadian system. The causal connections between depressive disorders and disturbed circadian rhythms have not been completely clarified. Chronobiological therapy is based on these disturbed processes. For the treatment of the circadian symptoms, various scientifically tested chronotherapeutics are available with however different effectiveness and evidence like light therapy or sleep deprivation. The successful treatment of depression also frequently leads to a improvement in altered circadian rhythm.