| Parkinson's Disease (PD) is a neurodegenerative condition associated with progressive deterioration of motor functions, resulting in tremor, rigidity, bradykinesia, postural instability, and gait dysfunction. Cognitive symptoms, which most strongly negatively impact attention and executive functions, are also common and can progress to the extent of impairing activities of daily living. Given the impact of these motor and cognitive symptoms on functionality, the emotional repercussions of PD can be devastating. In fact, depressive symptomatology is the most common psychological manifestation of PD (Nakabayashi et al., 2008). Furthermore, depressive symptomatology can negatively impact cognitive functioning, particularly working memory and attention (Foster et al., 2013). Recent research suggests that nonmotor symptoms of PD, such as depression, may be primary manifestations of the illness rather than solely repercussions of the functional impact of the illness (Chaudhuri, Odin, Antonini, & Martinez-Martin, 2011). Given the prominence of motoric symptoms, the emotional and cognitive repercussions of the disorder are often neglected in assessment and treatment. Although I hypothesized that each symptom cluster would contribute to predicting functional impairment, I predicted that cognitive and depressive symptoms would contribute to functional impairment above and beyond the contributions of motoric symptoms. These hypotheses were tested using hierarchical regression, controlling for demographic variables, to examine the extent to which motor, cognitive, and depressive symptoms predict functional impairment as rated by collateral and clinician informants. Results indicated that cognitive but not depressive symptoms predicted informant-rated functional impairment after controlling for motor symptoms. Both cognitive and depressive symptoms predicted clinician-rated functional impairment above and beyond the effects of motor symptoms. |
