What we know: Epidemiology

Iker Spozio


There has been a remarkable increase in the reported prevalence of autism, but the evidence does not bear out that we are in the midst of an autism ‘epidemic.’

What we know

  1. The latest survey from the U.S. Centers for Disease Control and Prevention (CDC) indicates that the prevalence of autism is 1 in 68 children in the U.S.
  2. The distribution in the U.S. is uneven, with a threefold variation among states.
  3. According to the CDC, prevalence more than doubled between 2002 and 2008 and increased tenfold over the past 20 years.
  4. Much of the reported increase in prevalence reflects the application of broader diagnostic criteria, greater availability of services and reduction in stigma associated with the diagnosis.
  5. Autism, across the entire spectrum, is four to five times more common in boys than in girls. The gender ratio is close to 1:1 in individuals with low intelligence quotients and 8:1 for high-functioning individuals.
  6. The incidence of autism increases with paternal age.
  7. Current evidence for specific environmental triggers is weak.

What is next?

  1. Do pockets of increased prevalence exist in certain communities?
  2. Is the prevalence of autism the same worldwide?
  3. Is autism underdiagnosed in girls?
  4. What accounts for the gender gap? Genetics? Environment?
  5. What social determinants influence the prevalence of autism?
  6. Do environmental risk factors influence the expression of autism risk genes?
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