Chronobiological treatments are non-pharmacological treatments that influence the circadian rhythms and the physiology of sleep. In these treatments, the sleep-wake cycle and exposure to environmental stimuli affecting the biological rhythms are controlled. The aim is to produce a therapeutic effect in the treatment of psychiatric disorders. Chronobiological treatments include manipulations of the sleep-wake cycle, like sleep deprivation and advanced sleep-wake rhythm, and scheduled exposures to light and darkness. The clinical use of chronobiological treatments in Finland has been minimal and limited to the treatment of mood disorders, especially depressive disorders.