title: The development of opposition-defiance during toddlerhood:  a population-based cohort study.
abstract: OBJECTIVE
  There is now emerging epidemiological evidence that a substantial proportion of toddlers in the general population may be experiencing a significant opposition-defiance problem before 2 years of age. This article describes the continuity and discontinuity in boys' and girls' opposition-defiance statuses during toddlerhood.
  
  
  METHODS
  Data came from The Québec Longitudinal Study of Child Development, a survey of a representative birth cohort of children from the Canadian province of Québec. A time-specific latent variables (Markov) model was used to estimate the proportion of toddlers who cease or start to exhibit oppositional-defiant behaviors (ODBs) on a frequent basis between 17 and 29 months of age and to test for gender differences therein.
  
  
  RESULTS
  A majority of toddlers who had exhibited ODBs on a frequent basis at 17 months of age were still doing so 1 year later. Also, a majority of toddlers who did exhibit ODBs on a frequent basis at 29 months of age had done so 1 year earlier. The results also show that there are more toddlers who start than stop exhibiting ODBs on a frequent basis during this period. Further, the continuity and discontinuity in toddlers' opposition-defiance statuses during this period did not vary between boys and girls, suggesting that gender differences in opposition-defiance have not yet emerged by the second half of the third year of life.
  
  
  CONCLUSIONS
  The predictive accuracy of early opposition-defiance is very good, with a substantial proportion of toddlers experiencing a significant opposition-defiance problem throughout toddlerhood.
authors.affiliation: Interdisciplinary School of Health Sciences, University of Ottawa, Ottawa, ON, Canada. raymond.baillargeon@uottawa.ca
authors.forename: Raymond H
authors.initials: RH
authors.lastname: Baillargeon
authors.forename: Kate
authors.initials: K
authors.lastname: Keenan
authors.forename: Guanqiong
authors.initials: G
authors.lastname: Cao
mesh_terms: D017668:Age of Onset; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000453:epidemiology / Q000209:etiology*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008390:Markov Chains; D011792:Quebec / Q000453:epidemiology; D012737:Sex Factors; D011795:Surveys and Questionnaires