Journal of Autism and Developmental Disorders

, Volume 31, Issue 5, pp 449–460

Birth Order Effects on Nonverbal IQ Scores in Autism Multiplex Families

  • Donna Spiker
  • Linda J. Lotspeich
  • Sue Dimiceli
  • Peter Szatmari
  • Richard M. Myers
  • Neil Risch
Article

DOI: 10.1023/A:1012217807469

Cite this article as:
Spiker, D., Lotspeich, L.J., Dimiceli, S. et al. J Autism Dev Disord (2001) 31: 449. doi:10.1023/A:1012217807469

Abstract

Lord (1992) published a brief report showing a trend for decreasing nonverbal IQ scores with increasing birth order in a sample of 16 autism multiplex families, and urged replication in a larger sample. In this report, analyses of nonverbal IQ scores for a sample of 144 autism multiplex families indicated that nonverbal IQ scores were significantly lower in secondborn compared with firstborn siblings with autism. This birth order effect was independent of gender as well as the age differences within sib pairs. No such birth order effects were found for social or communicative deficits as measured by the Autism Diagnostic Interview-Revised (ADI-R), but there was a modest tendency for increased scores for ritualistic behaviors for the firstborn sibs. Further, there were no gender differences on nonverbal IQ scores in this sample. Results are discussed in terms of implications for genetic studies of autism.

multiplex familiesbirth orderIQ scores

Copyright information

© Plenum Publishing Corporation 2001

Authors and Affiliations

  • Donna Spiker
    • 1
  • Linda J. Lotspeich
    • 1
  • Sue Dimiceli
    • 1
  • Peter Szatmari
    • 2
  • Richard M. Myers
    • 3
  • Neil Risch
    • 3
  1. 1.Division of Child Psychiatry and Child Development, Department of Psychiatry and Behavioral SciencesStanford University School of MedicineStanford
  2. 2.Department of Psychiatry, McMaster University Research BuildingChedoke-McMaster HospitalsHamiltonCanada
  3. 3.Department of GeneticsStanford University School of MedicineStanford