Time trends in autism diagnosis over 20 years: a UK population-based cohort study

Ginny Russell, Sal Stapley, Tamsin Newlove-Delgado, Andrew Salmon, Rhianna White, Fiona Warren, Anita Pearson, Tamsin Ford

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134 Citations (SciVal)

Abstract

Background: Autism spectrum disorder is a diagnosis that is increasingly applied; however, previous studies have conflicting findings whether rates of diagnosis rates continue to grow in the UK. This study tested whether the proportion of people receiving a new autism diagnosis has been increasing over a twenty-year period, both overall and by subgroups. Method: Population-based study utilizing the Clinical Practice Research Datalink (CPRD) primary care database, which contains patients registered with practices contributing data to the CPRD between 1998 and 2018 (N = 6,786,212 in 1998 to N = 9,594,598 in 2018). 65,665 patients had a diagnosis of autism recorded in 2018. Time trend of new (incident) cases of autism diagnosis was plotted for all, and stratified by gender, diagnostic subtypes, and developmental stage: infancy and preschool, 0–5 years old; childhood, 6–11 years old; adolescence, 12–19 years old; adults, over 19 years old. Results: There was a 787%, exponential increase in recorded incidence of autism diagnoses between 1998 and 2018; R 2 = 0.98, exponentiated coefficient = 1.07, 95% CI [1.06, 1.08], p <.001. The increase in diagnoses was greater for females than males (exponentiated interaction coefficient = 1.02, 95% CI [1.01, 1.03], p <.001) and moderated by age band, with the greatest rises in diagnostic incidence among adults (exponentiated interaction coefficient = 1.06, 95% CI [1.04, 1.07], p <.001). Conclusions: Increases could be due to growth in prevalence or, more likely, increased reporting and application of diagnosis. Rising diagnosis among adults, females and higher functioning individuals suggest augmented recognition underpins these changes.

Original languageEnglish
Pages (from-to)674-682
Number of pages9
JournalJournal of Child Psychology and Psychiatry
Volume63
Issue number6
Early online date19 Aug 2021
DOIs
Publication statusPublished - 30 Jun 2022

Bibliographical note

Funding Information:
We would like to dedicate this paper to our wonderful colleague, Andy Salmon (A.S.), who died during its production. He will be missed. The first author would like to acknowledge the generous support of the Wellcome Trust, Grant number: 108676/Z/15/Z. This study is based on data from the Clinical Practice Research Datalink (CPRD) obtained under license from the UK Medicines and Healthcare products Regulatory Agency. The data are provided by patients and collected by the NHS as part of their care and support. The authors have declared that they have no competing or potential conflicts of interest. S.S., G.R., and T.F. designed the study. G.R. wrote the first draft of the manuscript and made revisions. S.S., A.S., R.W., F.W., and G.R. collated and analyzed the data, and contributed to revision. T.F., T.N-D., A.P., S.S., and F.W. edited the manuscript.Key points Previous UK studies have conflicting findings as to whether rates of autism diagnosis are increasing. Ours is first study to analyze the time trend of autism diagnosis in a population-based UK clinical cohort by developmental stage, level of severity and by gender, over a twenty-year period. Results show an exponential increase in use of autism diagnosis over time. New subpopulations previously seldom considered for autism diagnosis (females, adults) have steepest growth in diagnosis rates. Differing rates of increase between subgroups suggest effects are primarily due to increased recognition, although an actual increase in autism incidence cannot be ruled out. 2009 UK policy to invest in adult assessment centers may underpin rise in adult diagnosis. Rising age at diagnosis in infancy and childhood suggests policy to improve early recognition of autism has had limited effect. Previous UK studies have conflicting findings as to whether rates of autism diagnosis are increasing. Ours is first study to analyze the time trend of autism diagnosis in a population-based UK clinical cohort by developmental stage, level of severity and by gender, over a twenty-year period. Results show an exponential increase in use of autism diagnosis over time. New subpopulations previously seldom considered for autism diagnosis (females, adults) have steepest growth in diagnosis rates. Differing rates of increase between subgroups suggest effects are primarily due to increased recognition, although an actual increase in autism incidence cannot be ruled out. 2009 UK policy to invest in adult assessment centers may underpin rise in adult diagnosis. Rising age at diagnosis in infancy and childhood suggests policy to improve early recognition of autism has had limited effect.

Funding Information:
We would like to dedicate this paper to our wonderful colleague, Andy Salmon (A.S.), who died during its production. He will be missed. The first author would like to acknowledge the generous support of the Wellcome Trust, Grant number: 108676/Z/15/Z. This study is based on data from the Clinical Practice Research Datalink (CPRD) obtained under license from the UK Medicines and Healthcare products Regulatory Agency. The data are provided by patients and collected by the NHS as part of their care and support. The authors have declared that they have no competing or potential conflicts of interest. S.S., G.R., and T.F. designed the study. G.R. wrote the first draft of the manuscript and made revisions. S.S., A.S., R.W., F.W., and G.R. collated and analyzed the data, and contributed to revision. T.F., T.N‐D., A.P., S.S., and F.W. edited the manuscript. Key points

Publisher Copyright:
© 2021 The Authors. Journal of Child Psychology and Psychiatry published by John Wiley & Sons Ltd on behalf of Association for Child and Adolescent Mental Health.

Keywords

  • Autism
  • autism spectrum disorder
  • clinical practice research datalink
  • diagnosis
  • primary care
  • time trends

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Developmental and Educational Psychology
  • Psychiatry and Mental health

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