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Autism phenotype versus registered diagnosis in Swedish children: prevalence trends over 10 years in general population samples

BMJ 2015; 350 doi: https://doi.org/10.1136/bmj.h1961 (Published 28 April 2015) Cite this as: BMJ 2015;350:h1961
  1. Sebastian Lundström, postdoctoral researcher12,
  2. Abraham Reichenberg, professor3,
  3. Henrik Anckarsäter, professor2,
  4. Paul Lichtenstein, professor4,
  5. Christopher Gillberg, professor1
  1. 1Gillberg Neuropsychiatry Centre, University of Gothenburg, Kungsgatan 12, 411 19, Gothenburg, Sweden
  2. 2Centre for Ethics, Law and Mental Health, University of Gothenburg, Sweden
  3. 3Departments of Psychiatry and Preventive Medicine, Mount Sinai School of Medicine, New York, NY, USA
  4. 4Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
  1. Correspondence to: S Lundström sebastian.lundstrom{at}gnc.gu.se
  • Accepted 13 March 2015

Abstract

Objective To compare the annual prevalence of the autism symptom phenotype and of registered diagnoses for autism spectrum disorder during a 10 year period in children.

Design Population based study.

Setting Child and Adolescent Twin Study and national patient register, Sweden.

Participants 19 993 twins (190 with autism spectrum disorder) and all children (n=1 078 975; 4620 with autism spectrum disorder) born in Sweden over a 10 year period from 1993 to 2002.

Main outcome measures Annual prevalence of the autism symptom phenotype (that is, symptoms on which the diagnostic criteria are based) assessed by a validated parental telephone interview (the Autism-Tics, ADHD and other Comorbidities inventory), and annual prevalence of reported diagnoses of autism spectrum disorder in the national patient register.

Results 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).

Conclusions The prevalence of the autism symptom phenotype has remained stable in children in Sweden while the official prevalence for registered, clinically diagnosed, autism spectrum disorder has increased substantially. This suggests that administrative changes, affecting the registered prevalence, rather than secular factors affecting the pathogenesis, are important for the increase in reported prevalence of autism spectrum disorder.

Footnotes

  • Contributors: SL, PL, and CG designed the study. SL performed all the analyses. SL and CG wrote the manuscript. HA, AR, and PL critically edited the manuscript. SL is guarantor of this work and had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

  • Funding: The Child and Adolescent Twin Study in Sweden study was supported by the Swedish Council for Working Life, funds under the ALF agreement, the Söderström-Königska Foundation, and the Swedish Research Council (Medicine and SIMSAM). The current study received no specific funding. The funding sources had no involvement in the study design; collection, analysis, and interpretation of the data; or the decision to submit this paper for publication.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: The data collection in the Child and Adolescent Twin Study in Sweden and the usage of the national patient register has ethical approval from the Karolinska Institutet ethical review board (Dnr 02-289 and 2010/507-31/1). No independent approval for any type of epidemiological study utilising this data is necessary.

  • Data sharing: The statistical code and datasets are available from the corresponding author at sebastian.lundström{at}gnc.gu.se.

  • Transparency: The lead author (SL) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

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