Date of Award

Spring 5-27-2015

Document Type


Degree Name

Doctor of Philosophy in Clinical Psychology (PhD)


Clinical Psychology

First Advisor/Committee Member

Amy H. Mezulis

Second Advisor/Committee Member

Lynette H. Bikos

Third Advisor/Committee Member

Jay R. Skidmore



This study assessed whether three potential cognitive and affective mechanisms mediated the relationship between physical activity and depressive symptoms. Participants were 143 young adults between the ages of 18 and 29 (M = 19.29, SD = 1.65); the majority of participants were female (72%) and Caucasian (69.9%). Participants were followed across eight weeks and completed measures of trait and state rumination, negative emotionality, cognitive style, depressive symptoms, and physical activity. A mediated model was proposed hypothesizing negative association between physical activity and depression mediated by less rumination, negative emotionality, and cognitive style. Hypotheses were examined cross-sectionally and prospectively. Contrary to hypotheses, physical activity was not associated with depressive symptoms concurrently (B = -.0010, 95% CI = -.007 to .005), prospectively for variability in physical activity [unstandardized coefficient = -0.0008, t(147) = -0.74, p = 0.462], or prospectively for aggregate mean of physical activity [unstandardized coefficient = 0.0013, t(144) = 0.88, p = 0.382]. Physical activity was not associated with any of the proposed mediators concurrently or prospectively meaning the first criterion was not met in establishing mediation. This study was a novel contribution to the literature as it explored theory-driven psychological mechanisms through which physical activity may confer protection for onset and maintenance of depressive symptomatology. Post hoc analyses highlight important aspects for future research to encompass, such as the need to prescribe physical activity for individuals experiencing depressive symptoms. Post hoc analyses were conducted and demonstrated areas for further research. Of note, physical activity was significantly correlated with depression for low CES-D individuals [r(85) = .236, p = .029] but not high CES-D individuals [r(58) = -.054, p = .689]. The low CES-D participants had a higher mean level of physical activity (M = 185.79, SD = 196.38) relative to the high CES-D people (M = 121.24, SD = 146.87). Due to lack of overall understanding of the mediators explaining the antidepressive effects of physical activity, the next step must be an intervention study. Clinical implications, limitations, and directions for future research are discussed.

Keywords: physical activity, depressive symptoms, rumination, negative cognitive style, negative emotionality