College of Science and Health Theses and Dissertations

Date of Award

Summer 8-22-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

First Advisor

Kathryn E. Grant, PhD

Second Advisor

Jocelyn Carter, PhD

Third Advisor

Susan Tran, PhD

Abstract

Accumulated, chronic stress exposure is well established as a precursor for allostatic load (AL). Both stress exposure and AL have been associated with depression in the existing literature. While many studies have focused on biomarkers representative of various physiological systems, a clear understanding of how physiological AL results in depression is yet unclear. Further, variability of hypo- and hypercortisolemic profiles have been associated with depression. A review of the existing literature supports hypocortisolemic profiles in relation to female depression and hypercortisolemic profiles in male depression across both adolescent and adult populations. The function of alpha-amylase (AA) dysregulation within the context of depression is even less well established. Previous research (Ali & Pruessner, 2012) has suggested a ratio of AA area under the curve with respect to ground (AUCg) over cortisol (CORT) AUCg, termed AOCg, as an indicator of the asymmetry between CORT and AA, and therefore, the hypothalamic pituitary adrenal (HPA) axis and sympathetic nervous system (SNS). Research supports an imbalance between these two systems may be representative of AL. AOCg has been correlated with major event exposure and depression in an adult sample. Adolescence is a sensitive biological period, perhaps posing even greater risk for the development of depressive symptoms within the context of AL. This provides rationale for use of the AOCg metric in an adolescent sample. A review of theory on stress research by Grant and colleagues (2003) posits a model for the etiology of psychopathology from stress exposure through the examination of potential biological mediators and moderators. The current study sought to further existing information on stress accumulation, AL, and depression by testing a path model with AUCg and area under the curve with respect to increase (AUCi) metrics of AA and CORT as mediators of the relationship between major events (ME), daily hassles (DH), and violent crime exposure (VC) with self-reported depression symptoms at two time points. We hypothesized that increased AUCg/AUCi of both CORT and AA would mediate the relationship between stressors and depression symptoms. We also hypothesized biological sex and parent depression severity would moderate the relationship between the physiological stress response and depression symptoms. In addition, the current study sought to replicate findings from the Ali & Pruessner study in an adolescent sample by running multiple regression analyses to identify associations between AOCg, stress, and depression symptoms. Results of the analyses indicate AUCg/AUCi metrics of AA and CORT do not mediate the relationship between stressors and depression symptoms. Regarding sex differences, female adolescents in the current sample exhibited a blunted response to the acute stressor task compared with males and presented with significantly more depression symptoms. AOCg was not significantly associated with depression symptoms in our adolescent sample but was significantly and positively associated with VC. Follow-up analyses indicate more VC is associated with lower COAg and that more COAg predicts less depression in adolescents. In addition, the use of more disengagement coping (DC) in response to more DH led to more depression symptoms at time one and lower AUCg AA values. Greater AUCg AA values in the current study were associated with less depression symptoms at time one and greater depression symptoms at time two. These results parallel previous studies demonstrating more SNS reactivity over time with failure to habituate contributes to changes in neurobiological processes that create vulnerability for increased depression symptoms (McCarty, 2016). The current study provided further support for the need to utilize multiple measures of the stress response to elucidate associations between specific stressor types and specific parts of the stress response system that may be most impacted. In addition, the current study added to the topic of AA measurement in adolescents by identifying an association between AA with a chronic, uncontrollable distal stressor (VC) and identifying a positive association between AA and depression symptoms over time in a community sample of adolescents

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