Book excerpt: Now expanded to two volumes, this invaluable reference work provides a comprehensive review of all information presently available about these disorders, drawing on findings and clinical experience from a number of related disciplines such as psychiatry, psychology, neurobiology, pediatrics, etc. The Handbook covers descriptive and diagnostic characteristics, biological contributions, intervention techniques, legal and social issues. The Third Edition is updated to include the newest work in animal models, genetics, neuropsychological processes, screening and assessment methods.