Graduation Year


Document Type




Degree Granting Department


Major Professor

Cynthia R. Cimino, Ph.D.

Committee Member

Jonathan Rottenberg, Ph.D.

Committee Member

Paul Spector, Ph.D.


Emotion, Mood, Motivation, Memory, Executive


Depression and apathy are two of the most common psychiatric symptoms in Parkinson's disease (PD) with prevalence estimates at higher rates than in medical populations with similar levels of disability. Several studies have provided evidence to suggest that apathy and depression are independent clinical phenomena that may differentially affect cognition. Recent research suggests that apathy may account for cognitive deficits over and above that of depression, especially in the domain of executive functioning. However, few studies have examined the independent influence of depression and apathy on cognitive abilities in patients diagnosed with PD using sensitive measures of specific cognitive domains. In addition, many have used measures of apathy and/or depression with symptom overlap, which may not adequately measure symptoms unique to the target construct.

The purpose of this study was to examine the independent influences of symptoms of depression and apathy on memory and executive functioning in patients diagnosed with PD using severity scales specifically designed to provide greater discrimination between symptoms. Depression severity was assessed using items that do not overlap with apathy symptoms or with somatic symptoms of PD itself. Apathy was measured using a scale previously shown to have little overlap with depressive symptoms.

Results revealed that apathy, but not depression, was significantly associated with executive functioning. In contrast, immediate memory was significantly associated with both apathy and depression. However, apathy accounted for added variance in memory scores when controlling for depression with marginal significance. When controlling for age, although less clear, these patterns remained.

Differentiation of apathy and depression and understanding their independent effects on cognitive functioning have several implications both for clinical intervention and for scientific investigation. Apathy not only has a negative impact on cognitive functioning, but also on daily functioning and caregiver burden/distress. Secondly, it has been associated with increased mortality as it may interfere with medication compliance. If appropriately identified, preliminary research suggests that symptoms of apathy may be medically treated independently of depressive symptoms. Distinguishing apathy and depression has robust implications for the advancement of psychological science, patient care, and for enhancing quality of life in patients and caregivers.