UCLA

Internalizing symptoms and disorders – such as anxiety and depression – increase in adolescence (Meyer and Lee, 2019) and can interact with youth brain and behavioral development. As youth develop, changing biological and environmental factors necessitate developing novel skills, such as emotion regulation and reward-based learning strategies, while balancing new drives toward risk-taking. Given how complex and in-flux this period of life is, investigating the role of internalizing symptoms in a variety of adolescent behaviors is crucial for better understanding how to support youth through this dynamic developmental stage. The studies in this dissertation examine how internalizing symptoms relate to brain development – specifically, functional connectivity and activity associated with emotion regulation and reward learning – as well as risk-taking in the real world. Chapter 1 provides a general introduction to the research outlined in the following chapters. Chapter 2 describes research relating internalizing symptomatology in subclinical youth to amygdala-whole brain functional connectivity. Findings demonstrate that the relationship between internalizing symptoms and amygdala connectivity is stronger in girls than boys, and that youth generally demonstrate greater connectivity between the amygdala and regions associated with emotional processing as a function of greater internalizing symptoms. In Chapter 3, findings from the first study to investigate brain and behavioral differences in emotion regulation between youth with and without anxiety are presented. Youth with anxiety regulated their emotions to the same extent as non-anxious peers; however, regulation may have been especially effortful for youth with anxiety as they demonstrated stronger prefrontal cortex activation and connectivity with the amygdala during regulation. Research presented in Chapter 4 characterizes the relationship between anxiety severity and reward learning in a subclinical sample. While all youth were capable of learning stimulus-reward associations, youth with higher anxiety allocated value toward non-rewarding stimuli to a greater extent and showed a stronger relationship between brain activity and behavior; furthermore, within this group, those with the highest intolerance of uncertainty showed the least reward network activation when receiving rewards. Finally, Chapter 5 examines racial disparities in the juvenile justice system, as well as tracks the longitudinal change in internalizing symptoms alongside criminal offending. Black youth, and to a slightly lesser extent Latino youth, faced the greatest disparities through system processing. All youth demonstrated greater improvements in internalizing symptoms alongside decreased offending, showing the tight relationship between mental health and criminal offending. Taken together, results from this dissertation demonstrate the varied effects of internalizing symptoms on adolescent brain and behavioral development. As such, these studies present a multi-disciplinary look at the role of mental health in the lives of adolescents.