Psychomotor retardation and risk of Parkinson's disease in unipolar depression: a retrospective cohort study

BackgroundDepression is associated with an increased risk of subsequent Parkinsons disease. Neuroimaging studies suggest a neurobiological overlap in mechanisms underlying Parkinsons disease and psychomotor retardation in depression. Our aim was to investigate whether, among individuals with depression, the presence of psychomotor retardation was associated with the development of subsequent Parkinsons disease. MethodsIn a retrospective cohort study, electronic healthcare records from individuals diagnosed with depression at age 40 or over in a large mental health service in London, UK were examined for the presence of psychomotor retardation. Linkage to general hospital records was used to ascertain diagnoses of Parkinsons disease between 2007 and 2023. Cox regression was used to compare the hazard of Parkinsons disease in individuals with depression with and without psychomotor retardation. ResultsAmong 6327 patients with depression, 2402 (38.0%) had psychomotor retardation. The adjusted hazard ratio for development of Parkinsons in those with psychomotor retardation was 1.43 (95% CI 1.02 - 2.01, p = 0.04). Secondary analyses demonstrated a significant difference in psychomotor retardation incidence at least 10 years before Parkinsons diagnosis. ConclusionsPsychomotor retardation in later-life depression is associated with increased risk of subsequent Parkinsons diagnosis over an extended period of time, suggesting that the relationship cannot solely be explained by misdiagnosis. Psychomotor retardation may therefore serve as a marker of prodromal Parkinsons disease. HighlightsO_LIPsychomotor retardation was associated with later Parkinsons disease. C_LIO_LIPsychomotor retardation may present >10 years prior to Parkinsons diagnosis. C_LIO_LIDepression with psychomotor retardation may be a prodrome for Parkinsons disease. C_LI