1. Aspergers Syndrome:
A milder form of the disorders of the autism spectrum, a child with Aspergers can have a good intellectual functioning but have deficits in the social functioning.
2. Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS):
It is a condition that lies between Aspergers syndrome and Autistic disorder in severity. Thus, children with this condition have symptoms more severe than Aspergers Syndrome but less severe than Autistic Disorder.
3. Autistic Disorder:
This condition has more severe symptoms than the above two along the Autism Spectrum Disorders.
4. Childhood Disintegrative Disorder:
This is rare but most severe among the disorders in this spectrum children with Childhood Disintegrative Disorder develop normally in the early years but suddenly start showing symptoms between the age 2-4, where they begin to lose communicative, social, motor and mental skills rapidly.