Sleep problems and circadian rhythms disturbances are common in many psychiatric disorders, with the mostoften-reported'sleep problem in most cases being insomnia. In this paper, the main findings about sleep disturbances (features and therapy) and other biorhythm disturbances (biological timekeepers, CLOCK genes, GSK3, melatonin, hypothalamo-pituitary-adrenal axis, body temperature) are reviewed in relation to schizophrenia, mood and anxiety disorders.