When the questions were reordered, the count doubled
Parent-reported autism in the National Health Interview Survey went from 1.25% to 2.24% in a single year. NCHS reordered the questionnaire; the children did not change.
We have not finished checking this source. No judgement either way. how we score evidence
Caveat on this rating: The doubling is not contested; its reach is limited by design, and the limits are the point. NHIS measures parent-reported "ever told," ages 3-17, with no records checked - it cannot be placed on one axis with CDC's records-based site network, and it cannot be read across its own 2014 and 2019 breaks as a single trend. One precision point carried from the verified record: NCHS's own language about the 2019 redesign is a hedge, not a prohibition. A flat NCHS sentence forbidding comparison across 2019 does not exist - it was searched for and not found - and the blunt "should not be directly compared" phrasing that circulates belongs to a different CDC programme page, not to NCHS survey documentation. Attribute it correctly or not at all.
The National Health Interview Survey measures something quite different from CDC's site network. Parents are asked whether a doctor or other health professional ever told them their child has autism, ages 3 to 17, and no records are checked. In 2014 the answer nearly doubled in one year.
Significant findings
The estimated prevalence of autism based on 2014 data was 2.24%, against an annualized 1.25% for 2011-2013 - a statistically significant increase. No population changes that fast. What changed was the form: NCHS reordered the developmental-disability questions for 2014, gave autism a standalone question, and named specific diagnoses inside it.
The authors say so themselves, in a paper whose title is the finding. "The revised question ordering and new approach to asking about developmental disabilities in the 2014 NHIS likely affected the prevalence estimates." The mechanism they describe is reallocation, not discovery - in earlier years "some parents of children diagnosed with ASD reported this developmental disability as other DD instead of, or in addition to, ASD." The corroboration is sitting in the other columns of the same table. While autism nearly doubled, "other developmental delay" fell from 4.84% to 3.57%, intellectual disability did not significantly change, and the prevalence of having any of the three conditions was constant across survey years. The same children, sorted into different boxes.
This is the cleanest measurement-artifact exhibit in the whole autism dataset, because it admits no etiologic reading at all. It also sets the reading rule for the rest of the series: NHIS breaks into short internally comparable segments at the 2014 questionnaire change and the 2019 survey redesign, and within those segments NCHS reports the movements were not statistically significant - neither 2014 to 2016 nor 2019 to 2021. The full series, with both breaks annotated, sits at www.resolv.social/topics/how-autism-got-counted.
Worth asking
When a survey number moves, the first question is whether the instrument moved, and for autism the answer is often yes. Ask which years a figure spans, whether the questionnaire changed inside that span, and whether the agency itself says the segments are comparable. If a number doubled in a year, something other than biology usually did the doubling - and it is worth knowing what before the figure is used to argue anything.
Source
Estimated Prevalence of Autism and Other Developmental Disabilities Following Questionnaire Changes in the 2014 National Health Interview Survey — Zablotsky B, Black LI, Maenner MJ, Schieve LA, Blumberg SJ (2015)
How this was scored
- Study design
- not recorded
- Funding
- not recorded
- Published in
- not recorded
- Sample size
- not recorded
- Preregistered
- not recorded
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
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Published August 31, 2026.
Questions
How strong is the evidence behind this?
Resolv rates this source "not yet assessed". We have not finished checking this source. No judgement either way. One caveat travels with that badge: The doubling is not contested; its reach is limited by design, and the limits are the point. NHIS measures parent-reported "ever told," ages 3-17, with no records checked - it cannot be placed on one axis with CDC's records-based site network, and it cannot be read across its own 2014 and 2019 breaks as a single trend. One precision point carried from the verified record: NCHS's own language about the 2019 redesign is a hedge, not a prohibition. A flat NCHS sentence forbidding comparison across 2019 does not exist - it was searched for and not found - and the blunt "should not be directly compared" phrasing that circulates belongs to a different CDC programme page, not to NCHS survey documentation. Attribute it correctly or not at all. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
Estimated Prevalence of Autism and Other Developmental Disabilities Following Questionnaire Changes in the 2014 National Health Interview Survey — Zablotsky B, Black LI, Maenner MJ, Schieve LA, Blumberg SJ (2015). The full source is linked on this page so you can read it yourself.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.