Date of Award

Summer 7-22-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Clinical Psychology (PhD)

Department

Clinical Psychology

First Advisor/Committee Member

Thane M Erickson

Second Advisor/Committee Member

Joel Jin

Third Advisor/Committee Member

Phillip Baker

Abstract

Depression is an increasingly common mental health concern and has been linked to both lifestyle factors and biological markers of inflammation. This study examined whether physical activity, dietary patterns, and religiosity/spirituality (R/S) predicted depression symptoms through their associations with high-sensitivity C-reactive protein (hs-CRP), a widely used biomarker of inflammation. Using data from the National Longitudinal Study of Adolescent to Adult Health, participants were assessed at Wave II (ages 12–20) and Wave IV (ages 24–32). Predictors included self-reported physical activity, proinflammatory and anti-inflammatory diet composites, and R/S engagement. Outcomes included concurrent and prospective depression symptoms, as well as hs-CRP concentrations. Results indicated that physical activity and R/S predicted lower concurrent depression symptoms and hs-CRP levels. Higher levels of proinflammatory diet predicted higher depression but not CRP. Mediation analyses supported an inflammatory mediational pathway, with physical activity and R/S concurrently predicting lower depression through lower CRP. However, most moderation effects and long-term prospective associations were not significant. These findings support a biopsychosocial model of depression in which lifestyle factors make unique, nonredundant contributions to mood and inflammation. Implications for clinical intervention and the inflammatory theory of depression are discussed.

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