Symptoms stayed flat while diagnoses climbed
A Swedish group measured autism symptoms in the population for ten years while registered diagnoses rose steadily over the same decade. The symptoms did not move.
We have not finished checking this source. No judgement either way. how we score evidence
Caveat on this rating: Scope, stated as the paper states it: Sweden, birth cohorts 1993-2002, with the phenotype measured by a validated parental telephone interview in a twin cohort and diagnoses taken from the national patient register. The authors say administrative changes "are important for" the increase - not that they account for all of it - and no decomposition in this literature attributes 100% of any rise to changed counting. A flat symptom trend in one country over one decade is strong evidence about that country and that decade; it is not a measurement of US surveillance counts, which use a different instrument again, and it must not be read as one.
The decomposition literature argues about what fraction of rising autism counts is changed counting, and every entry in it is a percentage with a confidence interval. One study sidesteps the arithmetic entirely, by measuring the two things separately in the same country over the same decade.
Significant findings
Lundstrom and colleagues assessed the autism symptom phenotype - the symptoms the diagnostic criteria are actually built on - annually in population samples of Swedish twins, using a validated parental telephone interview. They compared it against registered autism diagnoses in the national patient register. The phenotype sample was 19,993 twins; the diagnosis series covered all 1,078,975 children born in Sweden between 1993 and 2002.
The result is a clean divergence, and the paper states it plainly: "The annual prevalence of the autism symptom phenotype was stable during the 10 year period (P=0.87 for linear time trend). In contrast, there was a monotonic significant increase in prevalence of registered diagnoses of autism spectrum disorder in the national patient register (P<0.001 for linear trend)." The authors' own conclusion is that "administrative changes, affecting the registered prevalence, rather than secular factors affecting the pathogenesis, are important for the increase."
Symptoms flat, diagnoses rising, same decade, same country, two instruments pointed at the same population. It is the most legible exhibit in this literature precisely because it produces no percentage at all - the thing being measured did not move while the count of it climbed. The full decomposition section, with the studies that do produce percentages, sits at www.resolv.social/topics/how-autism-got-counted.
Worth asking
When a diagnosis becomes more common, the question worth separating is whether the underlying thing became more common or the counting did. Ask whether anyone has measured the two independently, because for most conditions nobody has. And note what this study does not claim: not that symptom trends are flat everywhere, and not that administrative change explains the whole of any country's rise. It shows a divergence in one place over one decade, which is a strong thing to show and a limited one.
Source
Autism phenotype versus registered diagnosis in Swedish children: prevalence trends over 10 years in general population samples — Lundström S, Reichenberg A, Anckarsäter H, Lichtenstein P, Gillberg C (2015)
Read the source: https://doi.org/10.1136/bmj.h1961
DOI: 10.1136/bmj.h1961
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: Scope, stated as the paper states it: Sweden, birth cohorts 1993-2002, with the phenotype measured by a validated parental telephone interview in a twin cohort and diagnoses taken from the national patient register. The authors say administrative changes "are important for" the increase - not that they account for all of it - and no decomposition in this literature attributes 100% of any rise to changed counting. A flat symptom trend in one country over one decade is strong evidence about that country and that decade; it is not a measurement of US surveillance counts, which use a different instrument again, and it must not be read as one. 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?
Autism phenotype versus registered diagnosis in Swedish children: prevalence trends over 10 years in general population samples — Lundström S, Reichenberg A, Anckarsäter H, Lichtenstein P, Gillberg C (2015). DOI: 10.1136/bmj.h1961. 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.