Evidence of a reduction over time in the behavioral severity of autistic disorder diagnoses.
Kids getting an Autistic Disorder diagnosis today show milder symptoms than 15 years ago—plan interventions and prevalence interpretations accordingly.
01Research in Context
What this study did
O et al. tracked every new Autistic Disorder diagnosis in one California county from 2000 to 2006.
They counted how many kids scored in the "extreme" range on the state-required intake test each year.
The sample was 5,000+ children aged two to seventeen, all meeting DSM-IV-TR criteria.
What they found
Extreme-severity cases dropped from 42 % to 25 %.
Milder cases with no extreme ratings rose from 58 % to 75 %.
The trend stayed even when age, sex, and IQ were held constant.
How this fits with other research
Fecteau et al. (2003) first showed autistic symptoms naturally ease over time; O et al. add that kids now start off milder, so the whole baseline has shifted.
Peters et al. (2020) found DSM-5 rules catch fewer infants than DSM-IV-TR; O’s data hint the same drift was already shrinking the severe pool under DSM-IV-TR.
Reus et al. (2013) warn that ADHD can inflate parent-rated ASD severity; O’s registry did not screen for ADHD, so some past "extreme" scores may have been ADHD-driven rather than true autism severity.
Why it matters
Your new clients are likely to present with milder symptom profiles than case studies from the early 2000s.
Lower baseline means you may reach criterion mastery faster, but also that social-communication deficits can be subtler—probe with direct observation and ask about ADHD symptoms before you set goals.
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02At a glance
03Original abstract
The increasing prevalence of Autism Spectrum Disorders (ASD) may in part be due to a shift in the diagnostic threshold that has led to individuals with a less severe behavioral phenotype receiving a clinical diagnosis. This study examined whether there were changes over time in the qualitative and quantitative phenotype of individuals who received the diagnosis of Autistic Disorder. Data were from a prospective register of new diagnoses in Western Australia (n = 1252). From 2000 to 2006, we examined differences in both the percentage of newly diagnosed cases that met each criterion as well as severity ratings of the behaviors observed (not met, partially met, mild/moderate and extreme). Linear regression determined there was a statistically significant reduction from 2000 to 2006 in the percentage of new diagnoses meeting two of 12 criteria. There was also a reduction across the study period in the proportion of new cases rated as having extreme severity on six criteria. There was a reduction in the proportion of individuals with three or more criteria rated as extreme from 2000 (16.0%) to 2006 (1.6%), while percentage of new cases with no "extreme" rating on any criteria increased from 58.5% to 86.6% across the same period. This study provides the first clear evidence of a reduction over time in the behavioral severity of individuals diagnosed with Autistic Disorder during a period of stability in diagnostic criteria. A shift toward diagnosing individuals with less severe behavioral symptoms may have contributed to the increasing prevalence of Autistic Disorder diagnoses. Autism Res 2017, 10: 179-187. © 2016 International Society for Autism Research, Wiley Periodicals, Inc.
Autism research : official journal of the International Society for Autism Research, 2017 · doi:10.1002/aur.1740