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

  • M. Posserud
  • Astri J. Lundervold
  • Stein Atle Lie
  • Christopher Gillberg
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

Authors and Affiliations

  • M. Posserud
    • 1
  • Astri J. Lundervold
    • 2
  • Stein Atle Lie
    • 3
  • Christopher Gillberg
    • 4
  1. 1.Centre for Child and Adolescent Mental HealthUnifob HealthBergenNorway
  2. 2.Department of Biological and Medical Psychology, Faculty of PsychologyUniversity of BergenBergenNorway
  3. 3.Centre for Child and Adolescent Mental HealthUnifob HealthBergenNorway
  4. 4.Child and Adolescent PsychiatryUniversity of GothenburgGöteborgSweden