Understanding biological and psychosocial Adult brain and depression

Adolescence is a period of significant neurodevelopment and increased vulnerability to the

onset of depression. However, the neural underpinnings of depression during adolescence

and the associated risk factors are not well understood. The aim of this PhD research was to

fill this knowledge gap by examining biological and psychosocial factors associated with the

emergence of depression during adolescence.

Using a large, population-based sample, the Adolescent Brain Cognitive Development (ABCD)

Study, my doctoral work found that depression in early adolescence is associated with

similar neuroimaging findings (cortical and white matter microstructural features) to

those seen in adult depression samples. Further, the work in this Book demonstrated

that earlier pubertal timing is associated with an increased risk for later depression in

adolescence. While earlier pubertal timing was also related to structural brain features,

brain structure was not found to mediate the observed association between early

pubertal timing and later depressive symptoms. This finding highlights the important role

that other aspects of a young person's biology, psychology and social world may play, and

should be explored in future work.

This Book also investigated how dynamic functional brain networks relate to irritability in

adolescent depression using a co-produced youth-researcher design. In this pilot study, I

first worked with young people to develop a novel fMRI irritability task that reflected the

social nature of irritability in adolescence. Using a local sample of youth with depressive

symptoms, I found that dynamic functional brain networks differed between the

irritability task and a standard resting state scan, which provides preliminary evidence for

validation of this novel task. Finally, my work demonstrated that properties of dynamic

brain networks related to emotion regulation and cognitive control were associated with

youth depressive symptoms and irritable mood.