Pervasive developmental disorders (PDDs) is an umbrella term used to define a class of disorders.

Disorders included in this class are:

• Autistic disorder.
• Rett's disorder.
• Asperger's disorder.
• Childhood disintegration disorder (CDD).
• Pervasive developmental disorders–not otherwise specified (PDD-NOS). This term is used to identify children who do not meet the diagnostic criteria for an established pervasive developmental disorder (PDD) but who have developmental and behavioral problems that are similar to those found in autism. These problems include abnormal sensitivities and unusual behavioral responses to certain situations. However, children with PDD-NOS have better cognitive and communication skills than children with autism or other types of PDDs.

Children with pervasive developmental disorders (PDDs) have difficulty in areas of social and emotional development, including:

• Developing relationships with other people, including their parents and children their own age.
• Communicating with other people.
• Having unusual behaviors and interests.

The severity of PDD varies by individual. Severely affected children are unable to function without significant help from parents and other caregivers. Other children are mildly affected and can develop adequate skills to lead independent lives as adults. Many children are affected at levels somewhere between these two extremes.

Pervasive developmental disorders are present at birth. However, the signs of these disorders may not be noticed until later, usually during the first 3 years of a child's life.