What causes autism spectrum disorder (ASD)?

Updated: Sep 30, 2019
  • Author: James Robert Brasic, MD, MPH; Chief Editor: Caroly Pataki, MD  more...
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Although the etiology of autism is unknown, hypotheses include genetic abnormalities, obstetric complications, exposure to toxic agents, and prenatal, perinatal, and postnatal infections. [12, 13, 14, 15]

Genetic studies have contributed to our understanding of the inheritance of ASD. A susceptibility to autism is likely associated with 400 to 1000 genes. [16] A heritability plays a role in 74% to 93% of the risk for ASD. [17] Increasing risk for ASD is independently associated with maternal age of 40 years and older, paternal age of 50 years and older, and interpregnancy intervals less than 24 months. [18, 19]

Maternal rubella is associated with significantly higher rates of autism and other conditions in children. Additionally, tuberous sclerosis is associated with autism as a comorbid disorder. [20] Approximately 10% of children with a pervasive developmental disorder exhibit a known medical condition. (See Etiology.)

On the other hand, anecdotal reports that autism may be linked with vaccinations (eg, for measles, mumps, and rubella) have not been supported by broader research. [21] Research from the CDC indicates that the number of childhood vaccines administered, either in a single day or during a child's first 2 years, has no effect on the risk of developing an autism spectrum disorder (ASD). According to results of a case-control study of more than 1000 children born between January 1994 and December 1999, exposure to antibody-stimulating proteins or polysaccharides from vaccines between the ages of 3 months and 2 years was not associated with an increased risk of developing an ASD. The study included 256 children with an ASD and 752 healthy controls. [22, 23] Parents should be encouraged to fully immunize their children. [24] (See Etiology.)

Effective treatment of associated behavioral problems includes intensive behavioral, educational, and psychological components. Interventions initiated at the time of diagnosis increase the likelihood of a favorable outcome. [25] Regular screening of infants and toddlers for symptoms and signs of autistic disorder is crucial because it allows for early referral of patients for further evaluation and treatment. (See Treatment.)

The initial clinical descriptions of autism suggested that cold, rejecting parents ("refrigerator mothers") caused autism in offspring; however, careful study of children with autism and their parents has disproved this hypothesis. Autism is not caused by a lack of warmth and affection in parents, nor by any other emotional or psychological parental deficits. Blaming parents for the development of autism in their children is inappropriate.

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