Neuropsychiatric features of Parkinson's disease in the era prior to the use of dopaminergic therapies.

Background: Psychosis in Parkinson's disease includes hallucinations and delusions. Other non-psychotic neuropsychiatric features include depression, anxiety and apathy. There is currently controversy over whether psychosis in Parkinson's is an intrinsic part of the disorder or the result of dopaminergic medications. This study aimed to examine a historical cohort of individuals with Parkinson's prior to the use of dopaminergic therapy to assess the prevalence of psychotic and other neuropsychiatric features.

Methods: The case notes of patients with Parkinson's disease admitted to the National Hospital for Neurology and Neurosurgery, London between 1924 and 1946 were examined. Demographic and clinical variables were extracted along with any neuropsychiatric features. Cases meeting criteria for encephalitis lethargica were excluded.

Results: 115 cases of individuals with Parkinson's disease were identified. 58 (41.7%) were female. Mean age was 54.0 (SD 9.6) years and mean time since Parkinson's diagnosis was 5.3 (SD 5.7) years. No individuals met criteria for encephalitis lethargica. No cases of hallucinations or delusions were reported. There was one case of an illusion in a patient who was using anticholinergic medication. Other neuropsychiatric features reported were sleep disorder (present in 10, 8.7%), depression (8, 7.0%), memory impairment (5, 4.3%), impulsivity (4, 3.5%), bradyphrenia (4, 3.5%), impaired attention (3, 2.6%), anxiety (1, 0.9%), fatigue (1, 0.9%) and apathy (1, 0.9%).

Conclusions: Prior to the use of dopaminergic therapies, patients with Parkinson's disease admitted to hospital rarely, if ever, reported psychotic symptoms, although other neuropsychiatric symptoms were more prevalent. The main limitation is that a lack of systematic enquiry about psychotic symptoms may have resulted in underreporting.