Emotional and cognitive social processes are impaired in Parkinson's disease and are related to behavioral disorders.

Objective: Parkinson's disease (PD) is associated with behavioral disorders that can affect social functioning but are poorly understood. Since emotional and cognitive social processes are known to be crucial in social relationships, impairment of these processes may account for the emergence of behavioral disorders.
Method: We used a systematic battery of tests to assess emotional processes and social cognition in PD patients and relate our findings to conventional neuropsychological data (especially behavioral disorders). Twenty-three PD patients and 46 controls (matched for age and educational level) were included in the study and underwent neuropsychological testing, including an assessment of the behavioral and cognitive components of executive function. Emotional and cognitive social processes were assessed with the Interpersonal Reactivity Index caregiver-administered questionnaire (as a measure of empathy), a facial emotion recognition task and two theory of mind (ToM) tasks.
Results: When compared with controls, PD patients showed low levels of empathy (p = .006), impaired facial emotion recognition (which persisted after correction for perceptual abilities) (p = .001), poor performance in a second-order ToM task (p = .008) that assessed both cognitive (p = .004) and affective (p = .03) inferences and, lastly, frequent dysexecutive behavioral disorders (in over 40% of the patients). Overall, impaired emotional and cognitive social functioning was observed in 17% of patients and was related to certain cognitive dysexecutive disorders. In terms of behavioral dysexecutive disorders, social behavior disorders were related to impaired emotional and cognitive social functioning (p = .04) but were independent of cognitive impairments.
Conclusions: Emotional and cognitive social processes were found to be impaired in Parkinson's disease. This impairment may account for the emergence of social behavioral disorders.
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