Electronic Theses and Dissertations





Document Type


Degree Name

Doctor of Philosophy


Counseling Psychology

Committee Chair

Suzanne Lease

Committee Member

Douglas Strohmer

Committee Member

Chrisann Schiro-Geist

Committee Member

Brandon Baughman


Background: While individuals diagnosed with Parkinsons disease (PD) often experience cognitive deficits, depression, and fatigue, the relationships among these non-motor sequelae throughout the progression of the disease are unclear. Objective: To examine the relationships among disease severity, depression, and fatigue and investigate the independent contributions of depression and fatigue to a composite measure of cognitive functioning, when controlling for disease severity in PD patients. Methods: A mixed retrospective and prospective sample of PD patients completed a comprehensive neuropsychological battery, as well as self-report measures of depression and fatigue. Cognitive functioning was represented by a summary statistic, or cognitive impairment index (CII). A hierarchal linear regression model, controlling for disease severity, examined the unique contributions of depression and fatigue on cognitive functioning. A Pearson correlation examined the relationship between depression and fatigue. Results: At step one, disease severity significantly contributed to the model, F(1, 41) = 48.06, p < .001, accounting for 52.8% of the variance in cognitive functioning. Introduction of depression and fatigue explained an additional 7.2% of the variance and this change in R2 was significant F(2,39) = 4.68, p < 0.05. Only depression continued to be a significant contributor beyond disease severity, t = 2.21, = 0.24, p < 0.05 and the change in the model was significant, F(1, 40) = 4.88, p < 0.05, R2 change = 0.05Conclusions: Findings suggest that depression is uniquely associated with cognitive functioning observed in PD patients independent of disease severity or level of fatigue. Interventions targeted towards depression may improve cognitive functioning.


Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.