Harvard Mental Health Letter

Autism spectrum disorders

Diagnosis and management involve time and patience.

The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) describes five pervasive developmental disorders: autistic disorder, childhood disintegrative disorder, Asperger's disorder, Rett's disorder, and pervasive developmental disorder not otherwise specified. Although they differ in some specifics, these disorders share three core features: impaired social interactions, difficulty in communicating with others, and repetitive or inflexible behavior. Recognizing that these disorders differ mainly in terms of severity, authors of the draft DSM-V, now undergoing review, have proposed deleting Rett's disorder and including the other four under the single category of autism spectrum disorder (ASD).

It remains unclear what causes an ASD, but most risk factors are genetic. When one identical twin develops an ASD, then 82% to 92% of the time the other one (who shares the same genes) will also develop the disorder. The concordance rate drops to 10% or less in fraternal twins, who share only some genes.

ASDs affect roughly one in 150 children, although some studies suggest the prevalence may be higher. ASD diagnoses have been increasing since the 1960s, but it remains unclear whether this is because of better awareness and assessment, or some unknown environmental factor that triggers these disorders in children who are genetically susceptible.

To continue reading this article, you must login.
  • Research health conditions
  • Check your symptoms
  • Prepare for a doctor's visit or test
  • Find the best treatments and procedures for you
  • Explore options for better nutrition and exercise
Learn more about the many benefits and features of joining Harvard Health Online »