Depression predicts the pattern of cognitive impairment in early Parkinson's disease.

OBJECTIVE: To estimate the pattern of cognitive impairment in early Parkinson's disease (PD) associated with depression. Also, the prediction of potentially relevant demographic/clinical factors in early PD on cognitive functioning was tested.

METHOD: The study comprised 80 consecutive early PD patients (16 with major depression (PDMD), 10 PD patients with dysthimic disorder (PDDD), and 54 nondepressed PD patients (PDND)). Thirty_seven healthy subjects matched for age, gender and education were also included in the study. The cognitive evaluation included the comprehensive classical neuropsychological battery and the Cambridge Neuropsychological Test Automated Battery (CANTAB).

RESULTS: The two different patterns of cognitive impairment in early PD patients were obtained even when the confounding influences of general cognitive abilities and motor slowness were taken in account. One pattern was common to all PD patients either they were depressed or not, and it is conceived etiologically as dysexecutive. The PDDD group presented only the quantitative increment of the common deficit observed in PD. The second pattern was present in PDMD patients, involved episodic/working memory and language deficits alongside with background executive impairment. Depression was extensively associated with the cognitive dysfunction in early PD, whereas severity of the disease, age at onset and treatment were less favorable as predictors.

CONCLUSIONS: This study provides evidence that the pattern of cognitive impairment in early PD may be predicted by depression severity. Therefore, the recognition and treatment of depressive disorder in early PD is important.