title: A prospective study of the emergence of early behavioral signs of autism.
abstract: OBJECTIVE
  To examine prospectively the emergence of behavioral signs of autism in the first years of life in infants at low and high risk for autism.
  
  
  METHODS
  A prospective longitudinal design was used to compare 25 infants later diagnosed with an autism spectrum disorder (ASD) with 25 gender-matched low-risk children later determined to have typical development. Participants were evaluated at 6, 12, 18, 24, and 36 months of age. Frequencies of gaze to faces, social smiles, and directed vocalizations were coded from video and rated by examiners.
  
  
  RESULTS
  The frequency of gaze to faces, shared smiles, and vocalizations to others were highly comparable between groups at 6 months of age, but significantly declining trajectories over time were apparent in the group later diagnosed with ASD. Group differences were significant by 12 months of age on most variables. Although repeated evaluation documented loss of skills in most infants with ASD, most parents did not report a regression in their child's development.
  
  
  CONCLUSIONS
  These results suggest that behavioral signs of autism are not present at birth, as once suggested by Kanner, but emerge over time through a process of diminishment of key social communication behaviors. More children may present with a regressive course than previously thought, but parent report methods do not capture this phenomenon well. Implications for onset classification systems and clinical screening are also discussed.
authors.affiliation: MIND Institute, University of California-Davis, Sacramento, California 95817, USA.
authors.forename: Sally
authors.initials: S
authors.lastname: Ozonoff
authors.forename: Ana-Maria
authors.initials: AM
authors.lastname: Iosif
authors.forename: Fam
authors.initials: F
authors.lastname: Baguio
authors.forename: Ian C
authors.initials: IC
authors.lastname: Cook
authors.forename: Monique Moore
authors.initials: MM
authors.lastname: Hill
authors.forename: Ted
authors.initials: T
authors.lastname: Hutman
authors.forename: Sally J
authors.initials: SJ
authors.lastname: Rogers
authors.forename: Agata
authors.initials: A
authors.lastname: Rozga
authors.forename: Sarabjit
authors.initials: S
authors.lastname: Sangha
authors.forename: Marian
authors.initials: M
authors.lastname: Sigman
authors.forename: Mary Beth
authors.initials: MB
authors.lastname: Steinfeld
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Young
mesh_terms: D017668:Age of Onset; D001321:Autistic Disorder / Q000175:diagnosis* / Q000523:psychology; D002648:Child; D002659:Child Development Disorders, Pervasive / Q000175:diagnosis* / Q000523:psychology; D002675:Child, Preschool; D003142:Communication; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D007223:Infant; D007805:Language Development Disorders / Q000175:diagnosis / Q000523:psychology; D008137:Longitudinal Studies; D008297:Male; D009048:Motor Skills; D010552:Personality Assessment; D011446:Prospective Studies; D012043:Regression, Psychology; D012189:Retrospective Studies; D012919:Social Behavior
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