A reanalysis of 1989 data suggests that diagnostic substitution may account for much of the increase in autism prevalence. Shaun Heasley reports at Disability Scoop:
The original study, published in 1989, looked at hundreds of Utah residents ages 3 to 25 who were suspected to have autism. Clinicians used DSM-III criteria to assess individuals as “diagnosed autistic” or “diagnosed not autistic” and ultimately found an autism prevalence rate of 4 in 10,000 in Utah at that time.
But when a research team from the University of Utah applied current diagnostic criteria from the DSM-IV-TR to records from participants in the two-decades-old study, they found that most who were deemed to be autism-free at that time would receive the label today.
What’s more, the study authors indicate that the vast majority of those who went overlooked in the original study had low IQ’s and would now be diagnosed with both autism and intellectual disability.
“Thus, while it is well known that current DSM-IV-TR criteria increased the identification of high functioning individuals, our results indicate that they also increase identification of ASD among individuals with autism and intellectual impairment,” wrote researchers in the study published online in the Journal of Autism and Developmental Disorders this month.
The analysis found that 59 percent of those who were “diagnosed not autistic” in the 1980s would qualify as having autism today, while an additional 38 percent of people in this group showed some characteristics of autism.