Social Psychiatry and Psychiatric Epidemiology

, Volume 45, Issue 3, pp 319–327

The prevalence of autism spectrum disorders: impact of diagnostic instrument and non-response bias


    • Centre for Child and Adolescent Mental HealthUnifob Health
  • Astri J. Lundervold
    • Department of Biological and Medical Psychology, Faculty of PsychologyUniversity of Bergen
  • Stein Atle Lie
    • Centre for Child and Adolescent Mental HealthUnifob Health
  • Christopher Gillberg
    • Child and Adolescent PsychiatryUniversity of Gothenburg
Original Paper

DOI: 10.1007/s00127-009-0087-4

Cite this article as:
Posserud, M., Lundervold, A.J., Lie, S.A. et al. Soc Psychiat Epidemiol (2010) 45: 319. doi:10.1007/s00127-009-0087-4



A large part of the variability in rates of autism spectrum disorders (ASD) across studies is non-aetiologic, and can be explained by differences in diagnostic criteria, case-finding method, and other issues of study design.


To investigate the effects on ASD prevalence of two methodological issues; non-response bias and case ascertainment. We compared the findings of using a semi-structured parent interview versus in-depth clinical assessment, including an ASD specific interview. We further explored whether including information on non-responders affected the ASD prevalence estimate.


A total population of 7- to 9-year olds (N = 9,430) was screened for ASD with the autism spectrum screening questionnaire (ASSQ) in the Bergen Child Study (BCS). Children scoring above the 98th percentile on parent and/or teacher ASSQ were invited to participate in the second and subsequently in the third phase of the BCS where they were assessed for ASD using the Development and Well-Being Assessment (DAWBA), and the Diagnostic Interview for Social and Communication disorders (DISCO), respectively.


Clinical assessment using DISCO confirmed all DAWBA ASD cases, but also diagnosed additional cases. DISCO-generated minimum prevalence for ASD was 0.21%, whereas estimated prevalence was 0.72%, increasing to 0.87% when adjusting for non-responders. The DAWBA estimate for the same population was 0.44%.


Large variances in prevalence rates across studies can be explained by methodological differences. Both information about assessment method and non-response are crucial when interpreting prevalence rates of ASD.


Autism spectrum disordersPrevalenceNon-response biasDiagnostic instrumentAssessment method

Copyright information

© Springer-Verlag 2009