Identifying the irritability dimension of ODD: Application of a modified bifactor model across five large community samples of children.

The importance of irritability, as measured among the symptoms of oppositional defiant disorder (ODD), has dramatically come to the fore in recent years. New diagnostic categories rely on the distinct clinical utility of irritability, and models of psychopathology suggest it plays a key role in explaining developmental pathways within and between disorders into adulthood. However, only a few studies have tested multidimensional models of ODD, and the results have been conflicting. Further, consensus has not been reached regarding which symptoms best identify irritability. The present analyses use 5 large community data sets with 5 different measures of parent-reported ODD, comprising 16,280 youth in total, to help resolve these questions. Across the samples, ages ranged from 5 to 18, and included both boys and girls. Confirmatory factor analyses demonstrated that a modified bifactor model showed the best fit in each data set. The structure of the model included 2 correlated specific factors (irritability and oppositional behavior) in addition to a general ODD factor. In 4 models, the best fit was obtained using the items "being touchy," "angry," and "often losing temper" as indicators of irritability. Given the structure of the models and the generally high correlation between the specific dimensions, the results suggest that irritability may not be sufficiently distinct from oppositional behavior to support an entirely independent diagnosis. Rather, irritability may be better understood as a dimension of psychopathology that can be distinguished within ODD, and which may be related to particular forms of psychopathology apart from ODD.