Intellectual Disability: Understanding its Development, Causes, Evaluation and Treatment

The estimated prevalence of intellectual disabilities is about 1%, which is roughly the same as the prevalence of schizophrenia. Despite this, books about the developmental, genetic, psychiatric, vocational, and family impact issues in the population with intellectual disabilities are rare compared with those on schizophrenia and other mental disorders. James C. Harris, a professor in psychiatry and pediatrics at Johns Hopkins University School of Medicine, has done an admirable job with this comprehensive book, which can be used as a reference or a textbook for psychiatrists, medical students, researchers, and treating professionals of all types.

Harris has meticulously reviewed a wide range of clinical research on etiology, prevalence, pathogenesis, and clinical features, including treatment and genetic issues, with an emphasis on behavioral genetics and the educational and social aspects of intellectual disability. His tenth and last chapter is devoted to ethics and spirituality, a subject seldom if ever addressed in a scientific publication.

Each chapter contains a thoroughly researched historical background of the subject, which adds perspective to the topic and stimulates the reader's interest. In the third chapter, entitled "The Classification of Intellectual Disability," Harris compares the various systems that are currently being used to diagnose and classify people with intellectual disability. Each system varies in slight details of definition and classification. He provides case vignettes to illustrate the differences between the tenth revision of the International Classification of Diseases, the DSM-IV, and the American Association on Mental Retardation (AAMR). Overall, the AAMR system is the most comprehensive. It emphasizes the parallel aspects of adaptive behavior and intellectual disability, the etiology, the environmental aspects, and the individual's desired outcomes, which can influence the environmental supports. One of the dimensions of the AAMR classification incorporates the World Health Organization's emphasis on functioning as described by the International Classification of Functioning, a framework for measuring health and disability.

In the seventh chapter, Harris exhaustively describes the known genetic causes of intellectual disability, behavior, and behavioral phenotypes. He goes into the details of the genetic influences on behaviors in several syndromes, including Down's syndrome, the velocardiofacial syndrome, fragile X syndrome, and others. Each description includes prevalence, genetics, prenatal testing, physical features, behavioral phenotype, cognitive profile, neuroimaging, and treatment.

Harris refuses to treat intellectual disability as a static condition but as an evolving process in the life span of a person. He details changes that can occur with proper diagnosis, treatment, care, and vocational placement. He touches on moral development and the role of the family.

Overall this is a remarkable and timely book that will be welcomed by all professionals and students who venture into the thorny field of intellectual disability.