Cohort effects explain the increase in autism diagnosis among children born from 1992 to 2003 in California
Open accessAbstract
BACKGROUND: The incidence and prevalence of autism have dramatically increased over the last 20 years. Decomposition of autism incidence rates into age, period and cohort effects disentangle underlying domains of causal factors linked to time trends. We estimate an age-period-cohort effect model for autism diagnostic incidence overall and by level of functioning. METHODS: Data are drawn from sequential cohorts of all 6 501 262 individuals born in California from 1992 to 2003. Autism diagnoses from 1994 to 2005 were ascertained from the California Department of Development Services Client Development and Evaluation Report. RESULTS: Compared with those born in 1992, each successively younger cohort has significantly higher odds of an autism diagnosis than the previous cohort, controlling for age and period effects. For example, individuals born in 2003 have 16.6 times the odds of an autism diagnosis compared with those born in 1992 [95% confidence interval (CI) 7.8-35.3]. The cohort effect observed in these data is stronger for high than for low-functioning children with an autism diagnosis. DISCUSSION: Autism incidence in California exhibits a robust and linear positive cohort effect that is stronger among high-functioning children with an autism diagnosis. This finding indicates that the primary drivers of the increases in autism diagnoses must be factors that: (i) have increased linearly year-to-year; (ii) aggregate in birth cohorts; and (iii) are stronger among children with higher levels of functioning.
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Factors other than diagnostic drift likely account for more than one-half of new ASD cases.
“In fact, these studies suggest that factors other than diagnostic drift likely account for more than one-half of new cases.”
From DNA methylation: a mechanism linking environmental chemical exposures to risk of autism spectrum disorders? (2016) · cites this paper as [8]
Independent studies have concluded that the increasing incidence of ASD cannot be explained entirely by increased awareness, broadening of diagnostic criteria, or improved detection.
“Independent studies have reached the common conclusion that this trend cannot be explained in its entirety by increased awareness, broadening of diagnostic criteria, or improved detection of ASD [ 5–8 ].”
From DNA methylation: a mechanism linking environmental chemical exposures to risk of autism spectrum disorders? (2016) · cites this paper as [8]
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- Authors
- Keyes, K. M., Susser, E., Cheslack-Postava, K., Fountain, C., Liu, K., & Bearman, P. S.
- Affiliations
- New York State Psychiatric Institute (US)
- Corresponding author
- Bearman, Peter S
- Venue
- International Journal of Epidemiology
- Publisher
- Oxford University Press (OUP)
- Published
- 2011-12-07
- Volume
- 41
- Issue
- 2
- Pages
- 495-503
- ISSN
- 0300-5771 (ISSN-L)
- 1464-3685
- PMC
- PMC3324454
- OpenAlex
- W2159197552
- Cited by
- 122
- References
- 34
- Citations by year
- 2026: 6 · 2025: 6 · 2024: 16 · 2023: 6 · 2022: 4 · 2021: 10 · 2020: 7 · 2019: 3 · 2018: 8 · 2017: 7 · 2016: 8 · 2015: 7 · 2014: 13 · 2013: 13 · 2012: 8
- FWCI
- 5.52
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- International Journal of Epidemiology (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- HighWire Press Open Archive (submittedVersion)
- Columbia Academic Commons (Columbia University)
- Funders
- National Institutes of Health (DP1OD003635)
- Eunice Kennedy Shriver National Institute of Child Health and Human Development (R24HD041022)
- Topics
- Life Sciences › Neuroscience › Cognitive Neuroscience › Autism Spectrum Disorder Research
- Health Sciences › Medicine › Psychiatry and Mental health › Child Nutrition and Feeding Issues
- Social Sciences › Psychology › Clinical Psychology › Family and Disability Support Research
- Keywords
- autism spectrum disorder, autism incidence, cohort effects, age-period-cohort model, temporal trends, high-functioning autism, low-functioning autism, birth cohort, California
- MeSH terms
- Age Factors, Autistic Disorder, California, Child, Child, Preschool, Female, Humans, Infant, Male, Risk Factors, Models, Statistical, Cohort Studies, Incidence, Prevalence
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