Objectives: Studies on neuropsychological functions in early Parkinson's disease (PD) have reported changes with respect to memory and executive control related to dysfunction of fronto-striatal circuitry. The question has been raised, however, whether these findings are at least partly influenced by depression, which as such can also lead to cognitive impairments that depend on the functional integrity of the prefrontal cortex.
Material and methods: In the present investigation early non-depressed PD patients (NPD), early PD patients with mild depressive symptoms (DPD), patients with primary depression (DEP) and healthy controls (HC) completed a range of neuropsychological tests.
Results: Group comparisons revealed impairments of DPD patients in comparison with HC with respect to verbal fluency, short-term memory and concept formation. In addition they showed mild working-memory deficits.
Conclusions: In summary the present results indicate that depressed mood in early PD may exacerbate cognitive impairments. Thus careful assessment of affective variables in PD should be an integral part of the treatment of PD.