Has our definition of autism changed over the years?
How people think about and diagnose autism has changed substantially since the diagnosis was first introduced nearly 75 years ago. In 1943, Leo Kanner firstcoined the term ‘infantile autism’ to describe children who seemed socially isolated and withdrawn.
In 1966, researchers estimated that about 1 in 2,500 children had autism, according to criteria derived from Kanner’s description. This and other early estimates of prevalence probably focused on children at the severe end of the spectrum and missed those with subtler features.
Autism didn’t make its debut in the DSM until 1980. In 1987, a new edition expanded the criteria by allowing a diagnosis even if symptoms became apparent after 30 months of age. To garner a diagnosis, a child needed to meet 8 of 16 criteria, rather than all 6 of the previous items. These changes may have caused the condition’s prevalence to tick above 1 in 1,400.
Then, in 1991, the U.S. Department of Education ruled that a diagnosis of autism qualifies a child for special education services. Before this time, many children with autism may instead have been listed as having intellectual disability. The change may have encouraged families to get a diagnosis of autism for their child. The number of children who have both a diagnosis of autism and intellectual disability has also risen steadily over the years.
In 1994, the fourth edition of the DSM broadened the definition of autism even further, by including Asperger syndrome on the milder end of the spectrum. The current version, the DSM-5, was released in 2013, and collapsed autism, Asperger syndrome and pervasive developmental disorder-not otherwise specified into a single diagnosis.
The most recent CDC estimate of autism prevalence is based on the fourth edition of the DSM. Future estimates will be based on DSM-5 criteria—which may lower autism rates.
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.
Is there no real increase in autism rates, then?
Awareness and changing criteria probably account for the bulk of the rise in prevalence, but biological factors might also contribute, says Durkin. For example, having older parents, particularly an older father, may boost the risk of autism. Children born prematurely also are at increased risk of autism, and more premature infants survive now than ever before.
選擇“Disable on www.wenxuecity.com”
選擇“don't run on pages on this domain”
