Frequency and correlates of involuntary emotional expression disorder in Parkinson's disease

Involuntary emotional expression disorder (IEED) is a syndrome characterized by involuntary episodes of emotional expression, particularly crying or laughing, that occur in patients with a neurological illness, including neuro-degenerative diseases. The authors assessed the frequency and clinical correlates of IEED among 131 patients with Parkinson's disease. IEED was present in 16.8% of patients overall and in 15.3% of depressed patients. The only clinical correlate of IEED diagnosis was greater severity of Parkinson's disease. The lack of an association between IEED and depression suggests that, in spite of some symptom overlap, the two disorders are distinct neuropsychiatric syndromes in Parkinson's disease.