The nature, structure, and neural signature of early life adversity

Abstract

The developing brain is shaped dynamically by our environmental experiences. One particularly salient environmental influence is that of adversity experienced in early life. The long-term consequences of such experiences on cognitive development and mental health outcomes are well-documented. However, there remain gaps in understanding the precise neuropsychological pathways through which these changes occur and why some individuals respond differently to similar exposures. This thesis advances this literature by investigating the relationship between childhood adversity and the brain, cognition and mental health using a data-driven, multi-level research framework that bridges behavioural, neural, and genetic levels of explanation in a large developmental cohort drawn from the Adolescent Brain and Cognitive Development study (ABCD). The first study explores cognitive markers of mental health in adversity-exposed youth using a hybrid machine-learning approach. The findings challenge existing theoretical models by demonstrating no specificity between the type or severity of exposure and cognitive function. They also suggest that cognition is not a relevant risk marker for mental health in adversity-exposed youth. The second empirical chapter investigates whether different forms of adversity relate to shared or unique variations in functional brain organisation using two complementary data-driven approaches. It demonstrates that the neural correlates of adversity are largely broad and non-specific, highlighting the utility of the functional connectome as a possible marker of mental health in adversity-exposed individuals. The final empirical chapter explores the interplay between genetic liability for mental illness, adversity, and the functional connectome using three unique methodological approaches. It identifies considerable overlap in the neural substrates of genetic liability for mental illness and childhood adversity. In the General Discussion, I delineate overarching themes that emerge all three empirical chapters and conclude by providing fruitful directions for future research to improve the reliability, utility, and integrity of adversity research.