"Autism (examined using ADOS) has remained stable in prevalence since 2007, at about one in a hundred adults (0.8%)."

"Autism (examined using ADOS) has remained stable in prevalence since 2007, at about one in a hundred adults (0.8%)." https://digital.nhs.uk/data-and-information/publications/statistical/adult-psychiatric-morbidity-survey/survey-of-mental-health-and-wellbeing-england-2023-24

Data released today (27th November 2025) from the Adult Psychiatric Morbidity Survey: Survey of Mental Health and Wellbeing, England, 2023/4.

It puts pay to the idea that there is any sort of equivalence in child and adult rates of autism (and that there ever has been). Said equivalent child autism rate is currently anywhere between 2-6% of school-aged children depending on what data you use.

We knew this of course, from the data from Tromans et al: e.g. Characteristics and primary care experiences of people who self-report as autistic: a probability sample survey of adults registered with primary care services in England https://pubmed.ncbi.nlm.nih.gov/39277196/ (based on self-report) and more.

It tells us, yet again, that the massive increase in autism prevalence is being driven by new childhood cases (autism is a childhood neurodevelopmental disorder so not really surprising). And also no, there aren't 'missing millions' of adults with undiagnosed autism as per what Adamou et al reported when they actually assessed adults who presented at clinic: Enhancing Adult Autism Diagnostic Pathways: The Role of Clinical Triage in Efficient Service Provision https://pubmed.ncbi.nlm.nih.gov/40363963/ (and proved that triage works).

So then, a question: what is causing huge numbers of children to present with and be diagnosed with autism? 

Well, only yesterday, some evidence that the words 'it's all genetic' are not a great explanation: e.g. As rates of ASD and ADHD rise, genetic contributions fall: Evidence for widening diagnostic criteria https://pubmed.ncbi.nlm.nih.gov/41292638/ which opens the door to issues like (a) widening diagnostic criteria and/or (b) environmental - non-genetic - factors 'causing' more autism. Or both?

Oh and keep in mind that despite the dogma, autism is not universally a lifelong condition for everyone e.g. https://pubmed.ncbi.nlm.nih.gov/31632036/ which may well partly explain why the adult autism rate is and has been so static for so many years...

Prenatal folic acid and multivitamin supplementation and offspring autism risk: umbrella-ified review

"Maternal prenatal folic acid and multivitamin supplementation are associated with a reduced risk of ASD [autism spectrum disorder] in offspring. These findings have important public health implications, suggesting that prenatal supplementation could help mitigate the risk of ASD in children." https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0334852

The results of an umbrella review that included 8 other systematic reviews or meta-analyses which themselves included over 100 studies which included several million mother-child pairs. In short, top tier evidence.

"Prenatal folic acid and/or multivitamin supplementation was associated with a 30% reduced risk of ASD in offspring (RR = 0.70, 95% CI: 0.62, 0.78; GRADE: highly suggestive). Subgroup analysis by supplement type showed that maternal prenatal multivitamin supplementation reduced the risk of ASD by 34% (RR = 0.66, 95% CI: 0.55–0.80; GRADE: highly suggestive), while folic acid supplementation was associated with a 30% reduction in ASD risk (RR = 0.70, 95% CI: 0.60–0.83; GRADE: highly suggestive)."

And yet again, folate metabolism and autism. 

The same folate metabolism and autism that is also US health policy now in terms of some autisms being potentially linked to cerebral folate deficiency (CFD) and/or folate receptor autoantibodies (FRAAs) meriting use of leucovorin (folinic acid). The difference being that in those areas - CFD and FRAAs - folic acid may not be the optimal supplement to use, as per why folinic acid (and perhaps even methylfolate) is instead being suggested for some children/adults with autism. Whether that might also translate into similar issues with folate metabolism for mums-to-be too as, being a risk factor for offspring autism, remains to be seen.

Nutritional factors being important to at least some autisms? Who'd have thunk that?