Book excerpt: The strong association between mental health and sleep is examined here in topics that include: Epidemiology of sleep disorders, co-morbidity with mental health disorders and impact on health and quality of life; Neurobiology of sleep; Neurobiology of circadian rhythms; Genetics of sleep disorders; Sleep disturbances in anxiety disorders; Sleep disturbances in mood disorders; Sleep disturbances in schizophrenia; Sleep disturbances in substance abuse disorders; Sleep disturbances and behavioral disturbances in children and adolescents; Sleep disturbances and behavioral disturbances in the elderly; Sleep disturbances and behavioral symptoms in medical patients; Effects of psychotropic medications on sleep continuity and sleep architecture; Circadian rhythm sleep disorders; New developments in sleep medications of relevance to mental health disorders; and Primary sleep disorders: identification and treatment by psychiatrists.