Autism spectrum disorder is a term used to include and replace all subtypes of autism, including autistic disorder, Asperger syndrome, childhood disintegrative disorder, and pervasive developmental disorder (not otherwise specified).
The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, published in 2013, defines autism spectrum disorder as follows:
A. persistent deficits in social communication and social interaction across contexts, not accounted for by general developmental delays
B. Restricted, repetitive patterns of behavior, interests, or activities
C. Symptoms must be present in early childhood (but may not become fully manifest until social demands exceed limited capacities)
D. Symptoms together limit and impair everyday functioning.
The 11th edition of the International Classification of Diseases and Related Health Problems, which is due for publication in 2019, is likely to define autism spectrum disorder as follows:
"Autism spectrum disorder is characterized by persistent deficits in the ability to initiate and to sustain reciprocal social interaction and social communication, and by a range of restricted, repetitive, and inflexible patterns of behaviour and interests. The onset of the disorder occurs during the developmental period, typically in early childhood, but symptoms may not become fully manifest until later, when social demands exceed limited capacities. Deficits are sufficiently severe to cause impairment in personal, family, social, educational, occupational or other important areas of functioning and are usually a pervasive feature of the individual’s functioning observable in all settings, although they may vary according to social, educational, or other context. Individuals along the spectrum exhibit a full range of intellectual functioning and language abilities."
Please see our detailed entry for Autism Spectrum Disorder