Date on Master's Thesis/Doctoral Dissertation

5-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Psychological and Brain Sciences

Degree Program

Clinical Psychology, PhD

Committee Chair

Sephton, Sandra E.

Committee Co-Chair (if applicable)

Salmon, Paul

Committee Member

Salmon, Paul

Committee Member

Cash, Elizabeth

Committee Member

Mast, Benjamin

Committee Member

Newton, Tamara

Author's Keywords

lung cancer; depression; mindfulness; biomarkers; survival

Abstract

Lung cancer patients experience high levels of distress, which commonly manifests as depressive symptoms. Importantly, depressive symptoms have demonstrated prognostic significance in cancer contexts, although the biological pathways by which depressive symptoms lead to poorer survival remain unclear and warrant greater attention. In addition to understanding the biological pathways by which depressive symptoms accelerate disease, identification of efficacious and effective psychological treatments for depressive symptoms are needed to improve both quality and quantity of life for cancer patients. Interventions that reduce depressive symptoms and improve downstream clinical outcomes are certainty needed; however, because many cancer patients face considerable burden, interventions that offer feasibility and accessibility are also desirable. Thus, this study has two primary aims: 1) to test the prognostic significance of depressive symptoms and explore the role of two biomarkers – cortisol and leukocyte telomere length (LTL) – as they relate to the depression-survival pathway and 2) to explore the ameliorative role of an iPod and mindfulness-based intervention on depressive symptoms and related outcomes among lung cancer patients. Non-small cell lung cancer patients (N = 67) who had received a diagnosis within five years were recruited to participate in the current study. Participants reported on depressive symptoms, provided a blood sample for LTL assessment, and collected home-based saliva samples for cortisol assessment at both baseline and at a three-month follow-up. Participants were invited to partake in an optional iPod and mindfulness-based pilot intervention that occurred between baseline and follow-up. The intervention involved listening to pre-recorded audio tracks adapted from the Mindfulness-based Stress Reduction program. A number of statistical tests, including ANCOVAs, hierarchical linear regressions, Cox Proportional Hazards regressions, and Kaplan-Meier analyses using the log rank test, were conducted to assess hypothesized relationships. Spearman’s rank-order correlations were used to assess theoretically derived control variables. Variables that were moderately related to outcomes (r > .3, < .5) were adjusted for. Regarding Aim 1, results revealed only clinical, not sub-clinical levels of depression at baseline predicted shorter survival; ethnic minorities evidenced greater shortening of LTL; and contrary to expectation, an increase in LTL was associated with shorter survival. Regarding Aim 2, results revealed that the intervention was associated with an increase in depressive symptoms and LTL and shorter survival. Although an increase in depressive symptoms was initially observed to be associated with a decrease in LTL, upon closer examination, there was an interaction effect. Post-hoc analyses revealed that as depressive symptoms increased, LTL only shortened among patients who did not participate in the intervention, whereas LTL lengthened among those who participated. Although results from the current investigation should be interpreted cautiously due to a number of limitations, these findings point to longer LTL as one potential biological explanation for the depression-survival relationship among lung cancer patients. Surprisingly, the less supported biomarker, LTL, as compared to cortisol, emerged as a potential link between depressive symptoms and shorter survival, a relationship that warrants continued attention and greater clarification. These results also cohesively suggest that the intervention was associated with poorer psychological and physical health and poorer clinical outcomes among this small sample of lung patients. Contrary to the intended and expected benefits of the pilot iPod- and mindfulness-based intervention, it yielded concerning negative associations that cannot be ignored. While a number of potential explanations for the current findings are discussed, elucidation of the components of the current intervention that may have worsened outcomes demand further investigation.

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