Sleep disturbances in individuals with psychological diseases may be a symptom of the underlying disease, a separate disturbance, or evidence of sleep-medicine conditions. Treatment is based on the cause, and may range from psychoeducational measures through behaviour therapy and drug approaches to mechanical forms of therapy. The book sums up all the essentials of sleep medicine for everyone treating people with sleeping disturbances in the field of psychological health care. It explains the foundations of sleep and sleeping disturbances and illustrates connections and interactions between sleeping disturbances and psychological diseases. Various procedures and options for diagnosis and treatment are discussed, as well as sociomedical aspects and consulting services for sleep disturbances.