Autism Spectrum Disorder: Incidence and Time Trends Over Two Decades in a Population-Based Birth Cohort.
Scott M Myers, Robert G Voigt, Robert C Colligan and 5 others
PMID 30519787WHAT IT FOUND
Clinically diagnosed autism kept increasing through 2004, while research-defined autism symptoms plateaued after the late 1990s.
This pattern was not consistent with a continued rise in true autism symptoms.
Key findings
01Among 31,220 individuals followed in the study cohort, 1,056 met inclusive research criteria for autism spectrum disorder and 242 had been clinically identified as having autism spectrum disorder.
02Clinical diagnosis incidence rose from 0.01 cases per 1000 person-years in 1985 to 1.28 cases per 1000 person-years in 2004, while inclusive research-defined incidence was not significantly different between 2000 and 2004.
03Across the 4 most recent birth periods, individuals met inclusive research criteria at younger ages, and the mean age at meeting criteria significantly decreased.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study relied on old medical and school records, so clinicians did not directly assess participants for the research. Some children with autism symptoms may have been missed if they never had a relevant diagnosis or school classification. Because signs and symptoms were counted from records, some cases could have been overidentified compared with clinical judgment. The county population was more racially homogeneous, wealthier, and more highly educated than the general U.S. population. The research definitions used older DSM-IV-TR criteria, not DSM-5. Calendar-year trends were only presented for a limited period because of how the birth cohort aged.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not read the rise in clinically diagnosed autism as proof that more children truly developed autism symptoms through the early 2000s. The study found clinically diagnosed cases kept increasing while research-defined cases plateaued. This pattern was not consistent with a continued rise in true autism symptoms.