Patients with Parkinson's disease (PD) typically present with motor symptoms, but several non-motor symptoms, such as cognitive impairment, autonomic dysfunction and neuropsychiatric symptoms, are usually also present, when adequately looked for. The objective of this paper is to provide an up-to-date, comprehensive review of the influence of affective disorders, mainly depression and apathy, on cognitive functioning of PD patients. Reviewed empirical findings suggest that, although depression and apathy have differential neurobiological bases in PD, both are associated to an increased risk of cognitive impairment, especially of executive functions, in this clinical population. The potential influence of other affective disorders, as anxiety and alexithymia, on cognitive functioning of PD patients is actually almost unknown and needs further empirical investigation. The clinical implication of these findings is that the best assessment and management of PD patients should include both neuropsychological and neuropsychiatric evaluations and the presence of non-motor symptoms as cognitive disturbances and affective features should be investigated with patients and caregivers.
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