Date of Award

5-2022

Document Type

Thesis

Degree Name

Master of Arts in Psychological Science

Department

Psychology

First Reader/Committee Chair

Jones, Jacob

Abstract

Parkinson’s disease (PD) is one of the most debilitating neurodegenerative diseases in the world. PD is typically characterized by its motor symptoms which commonly include tremors, rigidity, postural instability, and repetitive or involuntary muscle movements. Some of the most common non-motor symptoms include cognitive impairment, personality changes, depression, and anxiety. Depression has shown to be a prominent symptom in individuals with PD which affects them at any point during disease progression. However, it has been suggested that depression is more common among individuals with early-onset PD compared to individuals with later onsets. Our first aim investigated depression rates among individuals newly diagnosed with young (< 49 years old), middle (50-69 years old), and late onset Parkinson’s disease (> 70 years old). Our second aim investigated the neural correlates of depression among young (YOPD), middle (MOPD), and late onset PD (LOPD) individuals. The current study utilized data from the Parkinson’s Progression Marker’s Initiative (PPMI) database. The PPMI is a longitudinal multisite observational study to measure and identify biomarkers of Parkinson’s disease progression. The overall sample consisted of 487 newly diagnosed PD patients who completed a questionnaire of depression at each annual follow-up for a period of five years (aim 1). A subsample of 133 participants underwent head MRI at baseline and first annual follow-up to investigate the neural correlates of depression (aim 2). Multilevel modeling (MLM) examined longitudinal group differences in depression severity, and the association between depression and structural brain markers among age groups. Results for our first aim indicated a significant group X occasion interaction effect. More specifically, the LOPD group had higher depression scores overtime than the MOPD group in a model without medications. However, when medications were added in the model, these effects were no longer significant. Overall, this sample had an average score of 2.46 in the GDS-15 form suggesting that individuals were generally non-depressed. For our second aim, lower neuronal density in the frontal medial cortex was significantly associated with more depression in the MOPD group. Overall, our findings show that age of onset is significantly associated with depression severity between the LOPD and the MOPD groups. Furthermore, the frontal medial cortex significantly deteriorates over time as depression increases in the MOPD group.

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