The association between motor subtypes and psychopathology in Parkinson's disease

In Parkinson's disease (PD) it has been suggested that various motor subtypes are also characterized by a different prevalence and severity of specific non-motor symptoms such as cognitive deterioration, depression, apathy and hallucinations. The aim of this study was to investigate the association between motor subtypes and psychopathology in PD.

An exploratory and confirmatory cluster analysis of motor and psychopathological symptoms was performed with a randomized sample of 173 patients each, stemming from two research databases: one from Stavanger University Hospital and one from Maastricht University Hospital. These databases contained data of standardized assessments of patients with the Unified Parkinson's Disease Rating Scale, the Montgomery-Asberg Depression Rating Scale, and the Mini-Mental State Examination.

PD patients can be accurately and reliably classified into four different subtypes: rapid disease progression subtype, young-onset subtype, non-tremor-dominant subtype with psychopathology and a tremor-dominant subtype. Cognitive deterioration, depressive and apathetic symptoms, and hallucinations all cluster within the non-tremor-dominant motor subtype, that is characterized by hypokinesia, rigidity, postural instability and gait disorder.

This study shows that non-tremor-dominant PD is associated with cognitive deterioration, depression, apathy, and hallucinations, which has implications for future research into the pathophysiology of psychopathology in PD.