Investigating the Impact of Prenatal and Early Life Stress on Adolescent Cognitive and Physical Development

Abstract

Adolescence is a sensitive period of life shaped by environmental factors, including socioeconomic status (SES) and early adversity. While previous studies have linked early adversity to cognitive and physical outcomes, it remains unclear how these effects vary by income level or whether physical maturation mediates the influence of early adversity on cognition. This thesis investigates how early adversity—specifically prenatal stress and early life stress (ELS)—impacts adolescent cognitive development across income groups and explores whether physical development mediates these relationships. Using longitudinal data from the Adolescent Brain Cognitive Development (ABCD) Study, I compare cognitive and physical development between high- and low-income adolescents and apply linear mixed-effects models and mediation analyses to examine potential pathways. First, I show that high-income adolescents undergo earlier cognitive development, while low-income adolescents experience earlier physical development. Then, I demonstrate that both prenatal stress and ELS are significantly associated with cognitive and physical development in the high-income group, whereas only prenatal stress is significantly associated in the low-income group. This indicates that among low-income adolescents, the influence of ELS may be overshadowed by broader adversities prevalent in low-income environments. Expanding on this finding, I reveal that prenatal stress exerts a stronger influence than ELS on slowing cognitive development and accelerating physical development in the high-income group. Finally, I show that the timing of physical maturation does not mediate the relationship between early adversity and cognitive outcomes, suggesting that the stress acceleration hypothesis cannot be extended to cognitive development. I conclude by proposing that alternative mechanisms—such as emotional development—may better explain how prenatal stress and ELS shape cognitive trajectories, implying the need for interventions aimed at mitigating the long-term effects of early adversity on adolescent cognitive development.