Group of disorders characterized by delays in the development of socialization and communication skills; typical age of onset is before 3 years of age; symptoms may include problems with using and understanding language; difficulty relating to people, objects, and events; unusual play with toys and other objects; difficulty with changes in routine or familiar surroundings, and repetitive body movements or behavior patterns; autism is the most characteristic and best studied pdd; other types of pdd include asperger syndrome, childhood disintegrative disorder, and rett syndrome; prefer nts where possible.

The diagnostic category pervasive developmental disorders (PDD), as opposed to specific developmental disorders (SDD), was a group of disorders characterized by delays in the development of multiple basic functions including socialization and communication. It was defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM) (from 1980 to 2013), and the International Classification of Diseases (ICD) (until 2022). The pervasive developmental disorders included autism, Asperger syndrome, pervasive developmental disorder not otherwise specified (PDD-NOS), childhood disintegrative disorder (CDD), overactive disorder associated with mental retardation and stereotyped movements, and Rett syndrome...