title: Recurrence risk for autism spectrum disorders: a Baby Siblings Research Consortium study.
abstract: OBJECTIVE
  The recurrence risk of autism spectrum disorders (ASD) is estimated to be between 3% and 10%, but previous research was limited by small sample sizes and biases related to ascertainment, reporting, and stoppage factors. This study used prospective methods to obtain an updated estimate of sibling recurrence risk for ASD.
  
  
  METHODS
  A prospective longitudinal study of infants at risk for ASD was conducted by a multisite international network, the Baby Siblings Research Consortium. Infants (n = 664) with an older biological sibling with ASD were followed from early in life to 36 months, when they were classified as having or not having ASD. An ASD classification required surpassing the cutoff of the Autism Diagnostic Observation Schedule and receiving a clinical diagnosis from an expert clinician.
  
  
  RESULTS
  A total of 18.7% of the infants developed ASD. Infant gender and the presence of >1 older affected sibling were significant predictors of ASD outcome, and there was an almost threefold increase in risk for male subjects and an additional twofold increase in risk if there was >1 older affected sibling. The age of the infant at study enrollment, the gender and functioning level of the infant's older sibling, and other demographic factors did not predict ASD outcome.
  
  
  CONCLUSIONS
  The sibling recurrence rate of ASD is higher than suggested by previous estimates. The size of the current sample and prospective nature of data collection minimized many limitations of previous studies of sibling recurrence. Clinical implications, including genetic counseling, are discussed.
authors.affiliation: Department of Psychiatry, University of California-Davis, Sacramento, California 95817, USA. sally.ozonoff@ucdmc.ucdavis.edu
authors.forename: Sally
authors.initials: S
authors.lastname: Ozonoff
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Young
authors.forename: Alice
authors.initials: A
authors.lastname: Carter
authors.forename: Daniel
authors.initials: D
authors.lastname: Messinger
authors.forename: Nurit
authors.initials: N
authors.lastname: Yirmiya
authors.forename: Lonnie
authors.initials: L
authors.lastname: Zwaigenbaum
authors.forename: Susan
authors.initials: S
authors.lastname: Bryson
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Carver
authors.forename: John N
authors.initials: JN
authors.lastname: Constantino
authors.forename: Karen
authors.initials: K
authors.lastname: Dobkins
authors.forename: Ted
authors.initials: T
authors.lastname: Hutman
authors.forename: Jana M
authors.initials: JM
authors.lastname: Iverson
authors.forename: Rebecca
authors.initials: R
authors.lastname: Landa
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Rogers
authors.forename: Marian
authors.initials: M
authors.lastname: Sigman
authors.forename: Wendy L
authors.initials: WL
authors.lastname: Stone
mesh_terms: D002659:Child Development Disorders, Pervasive / Q000453:epidemiology*; D005192:Family Health; D005260:Female; D006801:Humans; D007223:Infant; D016014:Linear Models; D008297:Male; D012008:Recurrence; D035781:Siblings