Childhood Irritability: A Developmental Psychopathology Perspective

Ola Mohamed Ali, Western University

Abstract

Irritability, defined as a low threshold for anger, is a transdiagnostic feature of diverse forms of psychopathology and a rapidly growing literature implicates it in child maladaptation. Existing literature has focused on characterizing irritability in children with psychopathology, using conceptualizations and methods designed to assess more severely maladaptive behavior, usually via parent report. However, emerging work suggests that, even in the absence of dysfunction, normative variations in irritability are associated with increased risk for disorder, suggesting that irritability in childhood is a quantitatively distributed trait that covaries with vulnerability to psychopathology. Additionally, parent-report methods may be subject to an array of biases. Thus, our understanding of the development of irritability in typically developing children is limited by heterogeneity in conceptualizations of this important construct and the questionable psychometric properties of existing measures. As such, there is a clear need for a framework and complementary measures that conceptualize irritability as a quantitative trait that may go awry in development, giving rise to clinically significant maladaptation. Further, the interplay between childhood irritability and early contextual influences in shaping mental health outcomes is poorly understood. I address these gaps in this dissertation by examining irritability within a developmental psychopathology framework in a longitudinal sample of 409 (201 boys) typically developing children (M_{age at baseline} = 3.43 years) and their families. In Study 1, I examined the utility of an observational measure that conceptualizes irritability as a temperamental trait that reflects proneness to anger in contexts in which it is neither provoked nor appropriate. In Study 2, I examined the temporal stability of observationally assessed irritability across early childhood and interactions between early irritability and other influences in predicting later irritability. In Study 3, I examined the adolescent neural correlates of early irritability and its association with activity in brain regions implicated in emotion regulation. Findings support the validity and utility of observer-rated irritability, and shed light on the associations of irritability with external correlates that shape its development across childhood. Implications of this work for the measurement of irritability across its quantitative spectrum are discussed.