Our findings of a higher base rate of ODD among the adult sample (20.7%) compared to the child sample (9.7%) most likely reflects the different ways in which each sample was recruited (i.e., an attempt to recruit a cross-section of children in the SECCYD samples versus an attempt to oversample individuals with impulse and aggression problems in the adult sample). However, the overall finding of a dimensional structure of ODD for both the child and adult samples suggests that, the underlying structure of the construct remains the same. Our findings have important implications for the assessment and diagnosis of ODD across the lifespan and can inform further developments for treatments of the disorder for children and adults. Specifically, dimensional approaches to the assessment of ODD, with items that assess the full range of ODD symptomatology should be superior to assessment instruments designed to determine if respondents meet a diagnostic threshold (i.e., determining the ideal cut score for identifying those with ODD is likely to be a futile exercise). Additionally, because dimensional constructs likely result from the combination of multiple etiological
