Pervasive Developmental Disorder
According to the National Institute of Mental Health, there are five pervasive developmental disorders, also called autism spectrum disorders. The most common are autistic disorder (most often just called autism), Asperger’s syndrome and “pervasive developmental disorder not otherwise specified” (PDD-NOS). The other two PDD’s, Rett syndrome and childhood disintegrative disorder, are very severe but also very rare so they will not be discussed here.
It is usually obvious within the first three years of a child’s life if they suffer from severe autism, Rett syndrome or CDD. However, some children escape diagnosis until they enter school; in fact, some with high-functioning autism or Asperger’s syndrome may escape diagnosis altogether or will be misdiagnosed.
Children with autism may also have other conditions which make diagnosing them even more difficult, such as mental retardation, Tourette’s syndrome, and seizure disorders; learning disabilities such as ADD or ADHD; or psychological conditions such as depression.
Pervasive Development Disorder – Not Otherwise Specified (PDD-NOS)
According to the NIND, “Children with PDDNOS either (a) do not fully meet the criteria of symptoms clinicians use to diagnose any of the four specific types of PDD above, and/or (b) do not have the degree of impairment described in any of the above four PDD specific types.”
A child is placed into this category when there is a severe and pervasive impairment in the development of social interaction or verbal and nonverbal communication skills, or when stereotyped behavior, interests, and activities are present, but the criteria are not met for the PDD’s discussed above nor for schizophrenia or other psychiatric conditions.