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Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Psychology

Supervisor

Hayden, Elizabeth P.

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 (Mage 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.

Summary for Lay Audience

Irritability, described as a proneness to anger and frustration that manifest as severe and frequent temper outbursts, is a symptom of many childhood mental health disorders. However, even healthy children who do not meet criteria for a psychiatric diagnosis vary in their proneness to anger. Recent research has found that irritable children, even in the absence of a mental health disorder, are also at a higher risk for developing a mental health problem later in life. Understanding the nature of early irritability and elucidating the processes that shape its development across childhood are important towards predicting risk and identifying targets for early intervention. However, most of the research that has been conducted on irritability has focused on children who already have a mental health disorder, making it difficult to separate irritability from other symptoms of disorder so that we can study its normal development. Additionally, most of the measurement tools used to assess childhood irritability have been developed for capturing extreme manifestations and do not adequately measure irritability in typically developing children. Observing children’s behaviors while they engage in tasks that resemble everyday activities can provide more accurate information about the nature of irritability in healthy children. I investigated the validity of assessing irritability using an observational laboratory measure of child behavior in a sample of 409 healthy, 3-year-old children, and tested whether irritability measured this way is predictive of later symptoms of psychopathology (Study 1). In Study 2, I examined whether observer-rated irritability remains relatively stable at age 5 years and studied the contribution of within-child and contextual factors (e.g., parenting) in predicting its trajectory. In Study 3, I investigate the association between early irritability and functioning of brain regions involved in emotion control, during adolescence. Across these studies, I found evidence for the validity of irritability measured observationally and found associations between irritability in healthy children and markers of risk implicated in psychopathology. These findings highlight the importance of studying irritability in healthy children towards informing our understanding of the mechanisms that lead to the development of mental health disorders.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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