Psychiatric morbidity in patients with Parkinson's disease.

Forty patients with Parkinson's disease underwent a detailed assessment of their psychiatric state using a standardized, semi-structured interview, the Present State Examination. Analysis of the interviews yielded a profile of depressive and neurotic syndromes. Comparing the results with population norms, however, revealed that the patients were distinguished only by high levels of depressed mood and loss of interest and poor concentration. In the majority of patients the range and severity of symptoms fell below the criteria for 'caseness'. Only four patients could be allocated to an ICD-9 class, two to 'neurotic depression', one to 'anxiety state' and one to 'phobic state'. This rate was almost identical to that found in the general population. Broader indices of psychiatric morbidity were related to the patients' levels of disability and cognitive function.