title: Social and communication development in toddlers with early and later diagnosis of autism spectrum disorders.
abstract: BACKGROUND
  To our knowledge, no prospective studies of the developmental course of early and later diagnosis of autism spectrum disorders from 14 months of age exist.
  
  
  OBJECTIVE
  To examine patterns of development from 14 to 24 months in children with early and later diagnosis of autism spectrum disorders.
  
  
  METHODS
  Prospective, longitudinal design in which 125 infants at high and low risk for autism were tested from age 14 to 36 months. Comprehensive standardized assessments included measures of social, communication, and play behavior.
  
  
  METHODS
  Testing occurred at a major medical and research institution as part of a large, ongoing longitudinal study.
  
  
  METHODS
  Low-risk controls (n = 18) and siblings of children with autism, grouped on the basis of outcome diagnostic classification at 30 or 36 months: autism spectrum disorders (early diagnosis, n = 16; later diagnosis, n = 14), broader autism phenotype (n = 19), and non-broader autism phenotype (n = 58).
  
  
  METHODS
  Social, communication, and symbolic abilities were assessed.
  
  
  RESULTS
  Social, communication, and play behavior in the early-diagnosis group differed from that in all other groups by 14 months of age. By 24 months, the later-diagnosis group differed from the non-autism spectrum disorder groups in social and communication behavior, but not from the early-diagnosis group. Examination of growth trajectories suggests that autism may involve developmental arrest, slowing, or even regression.
  
  
  CONCLUSIONS
  This study provides insight into different patterns of development of children with early vs later diagnosis of autism spectrum disorders.
authors.affiliation: Kennedy Krieger Institute, Center for Autism and Related Disorders, The Johns Hopkins School of Medicine, Baltimore, Maryland 21211, USA.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Landa
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Holman
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Garrett-Mayer
mesh_terms: D000367:Age Factors; D001321:Autistic Disorder / Q000175:diagnosis* / Q000235:genetics / Q000523:psychology; D002657:Child Development / Q000502:physiology*; D002675:Child, Preschool; D003147:Communication Disorders / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D002658:Developmental Disabilities / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D007223:Infant; D007807:Language Tests / Q000706:statistics & numerical data; D008137:Longitudinal Studies; D008297:Male; D009633:Nonverbal Communication / Q000502:physiology; D010555:Personality Inventory / Q000706:statistics & numerical data; D010641:Phenotype; D010988:Play and Playthings / Q000523:psychology; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D012307:Risk Factors; D035781:Siblings / Q000523:psychology; D012919:Social Behavior; D012951:Socialization; D018709:Statistics, Nonparametric