A new survey published in the journal Pediatrics suggests that the prevalence of autism continues to rise. An estimated 1.1% of children between the ages of 3 and 17 are affected by conditions on the autism spectrum.
Estimates of autism prevalence prior to 1980 were below 0.05%. By the early 2000s, widely publicized estimates went as high as 0.7%. There is currently no scientific consensus on the reason for this dramatic change.
This new paper does appear to put the final nail in the coffin of the hypothesis that the increase in prevalence is due to increased awareness of the condition and improved diagnostic methods. Of the 1.1% of children with autism, 17% (0.2% of the population) were reported to be severely affected. Since it is hard to imagine severely autistic children evading diagnosis, the observation that severe autism is 4 times more prevalent than any autism was a generation ago is a compelling argument for a more immediate cause.
Increases in autism prevalence may also necessitate revising the current belief that the condition has a largely genetic basis. Twin and sibling studies have demonstrated a higher prevalence than the general population, indicating a likely genetic component. Still, genetics alone would have difficulty explaining such a dramatic prevalence spike.