Effects of Psychosocial Stress and Depression on Cardiovascular Health in Youth: A Longitudinal Investigation

Abstract

Recent evidence suggests that cardiovascular disease (CVD) may be impacted by psychological distress, and specifically the experience of stress and depression. The evidence has been most clearly established in adults and, for the most part, limited to brief point-in-time measures of distress. With increasing recognition that early signs of psychosocial stress and depression, as well as the processes leading to CVD may begin to emerge in childhood, the question then presents itself as to whether psychological distress, experienced earlier in the life course, influences early pathogenesis for CVD. The current research sought to determine whether symptoms of psychosocial stress and depression, experienced earlier in the life course, negatively influenced a set of established behavioural and metabolic risk factors and prognostic markers for CVD. Investigations in this thesis were conceptualised within a life course framework, but with an emphasis on the paediatric stage of development. Therefore, relationships between psychological constructs and CVD risk factors and risk markers were investigated as they were likely to present in this younger age group; beginning with primordial risk factors - risk factors that may underlie conditions leading to CVD rather than to causation directly, followed by intermediary markers - those considered to be prognostically significant of later CVD. Initially, two clusters of primordial risk factors were investigated in two separate studies. Firstly, the impact of psychosocial stress and depressive symptoms on a set of behavioural risk factors, namely physical inactivity and cardiorespiratory fitness were investigated. Findings from this study indicated that a change in depressive symptoms within a child had a direct impact on their cardiorespiratory fitness and that children identified with more symptoms of stress and depression were more likely to be less physical activity and less fit. In the second study, investigations examining the influence of psychosocial stress and depressive symptoms on a set of metabolic primordial risk factors, namely percent body fat and insulin resistance, revealed a dose-response relationship between insulin resistance and depressive symptoms, whereby boys with higher levels of insulin resistance also reported more symptoms of depression, and a direct (longitudinal) effect indicating that boys who increased in depressive symptoms also became fatter. In Study 3 and Study 4, investigations were extended to include a set of intermediary risk makers of CVD, those considered to be prognostically significant of later CVD. The effect of psychosocial stress and depressive symptoms on arterial stiffness and blood pressure were investigated in study 3; and on endothelial function in study 4. Findings from these studies demonstrated that children who became more depressed also had increases in diastolic blood pressure and mean arterial pressure; and that those becoming more stressed had a reduction in pulse pressure; but thus far did not uncover a direct effect of psychosocial stress or depression on arterial stiffness or endothelial function in our cohort. Overall, this thesis builds a case for the impact of psychosocial stress and depressive symptomology on CVD risk among growing children. The implications for these findings in terms of intervention and further research are discussed.