Has the rising awareness of autism contributed to the prevalence?
Increased awareness of autism has undoubtedly contributed to its rise in prevalence, Durkin says.
Until the 1980s, many people with autism were institutionalized, rendering them effectively invisible. Studies show that parents who are aware of autism’s presentation—by living near someone with the condition, for example—aremore likely to seek a diagnosis for their children than parents with no knowledge of the condition. Living close to urban centers and having access to good medical care also boost the likelihood of diagnosis.
Greater awareness of autism is also likely to boost CDC estimates by increasing the chances that autism traits, such as lack of eye contact, show up in school and medical records, says Fombonne.
Policy changes may have also played a role. In 2006, the American Academy of Pediatrics recommended screening all children for autism during routine pediatrician visits at 18 and 24 months of age. This move may have led to diagnoses for children who would otherwise have slipped under the radar.
Are there other factors that have influenced prevalence?
Many individuals diagnosed with autism may, in the past, have been misdiagnosed with other conditions, such as intellectual disability: As diagnoses of autism have risen, those of intellectual disability have decreased.
What’s more, a diagnosis of autism gives children greater access to specialized services and special education than do diagnoses of other conditions. This benefit makes clinicians more likely to diagnose a child with autism, even those who are on the borderline of the clinical criteria.
Prior versions of the DSM did not allow for children to be diagnosed with both autism and attention deficit hyperactivity disorder. The DSM-5 allows multiple diagnoses, and most children with developmental delay are routinely screened for autism.
Autism prevalence has traditionally been highest in white children in the U.S, but this is starting to change. African-American and Hispanic children have lower rates of diagnosis because of a lack of access to services. Widespread screening has improved detection of autism in these groups, and raised overall prevalence.