Cognitive performance in nondemented nonpsychotic Parkinson disease patients with or without a history of depression prior to the onset of motor symptoms.

In Parkinson disease (PD), cognitive impairment is common, occurs mainly in the form of milder deficits (as opposed to dementia), and commonly coincides with depression. In this cross-sectional study, we evaluated whether depression that existed before the onset of typical motor symptoms (pre-PD depression) reflected on the actual cognitive performance. Nondemented nonpsychotic PD patients with (test, n = 27) and without (control, n = 112) a history of pre-PD depression, caliper-matched for age, education, and disease duration were assessed for motor and nonmotor disease characteristics and in a battery of cognitive tests. Test patients had higher actual depression/anxiety levels. Gradual multivariate and mediation analysis indicated unfavorable effects of pre-PD depression on cognition: a direct effect on mental set shifting/response inhibition (independent of actual depression/ anxiety or other factors); and indirect effects on other cognitive domains mediated through the increased depression/anxiety. Data suggest that pre-PD depression favors poorer cognitive abilities in nondemented patients at a given time after PD has been diagnosed.