title: Broader autism phenotype: evidence from a family history study of multiple-incidence autism families.
abstract: OBJECTIVE
  Studies of families ascertained through a single autistic proband suggest that the genetic liability for autism may be expressed in nonautistic relatives in a phenotype that is milder but qualitatively similar to the defining features of autism. The objective of this study was to examine behaviors that may define this broader phenotype in relatives ascertained through two autistic siblings.
  
  
  METHODS
  The authors used a semistructured family history interview to compare the rates of social and communication deficits and stereotyped behaviors in relatives ascertained through two autistic siblings (families with multiple-incidence autism; 25 families) with the rates in relatives of Down syndrome probands (30 families).
  
  
  RESULTS
  Higher rates of social and communication deficits and stereotyped behaviors were found in the relatives in the families with multiple-incidence autism.
  
  
  CONCLUSIONS
  These data suggest that further studies should be undertaken to delineate the boundaries of the broader autism phenotype and that this broader phenotype should be included in some future genetic analyses of this disorder.
authors.affiliation: Department of Psychiatry, University of Iowa College of Medicine, Iowa City, USA. jpiven@blue.weeg.uiowa.edu
authors.forename: J
authors.initials: J
authors.lastname: Piven
authors.forename: P
authors.initials: P
authors.lastname: Palmer
authors.forename: D
authors.initials: D
authors.lastname: Jacobi
authors.forename: D
authors.initials: D
authors.lastname: Childress
authors.forename: S
authors.initials: S
authors.lastname: Arndt
mesh_terms: D000293:Adolescent; D000328:Adult; D001321:Autistic Disorder / Q000175:diagnosis / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D003147:Communication Disorders / Q000175:diagnosis / Q000235:genetics; D004314:Down Syndrome / Q000175:diagnosis / Q000235:genetics; D005190:Family; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D015999:Multivariate Analysis; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D012737:Sex Factors; D012951:Socialization; D013239:Stereotyped Behavior