Background: This study examined the age- and gender-specific risk of depression in demented and non-demented participants, its symptom structure, and associated clinical factors in a nationwide random sample of n = 1449 outpatients with Parkinson disease (PD).
Methods: Depression ratings were based on a cross-sectional clinical assessment including the clinical Montgomery-Asberg Depression Rating Scale (MADRS > or = 14). Parkinson disease severity was rated according to Hoehn and Yahr (HY) and the Unified Parkinson's Disease Rating Scale. Diagnosis of dementia was based on Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition; DSM-IV) criteria.
Results: 25.2% (CI: 22.8-27.5) of all patients met study criteria for depression. Additionally, 8.4% of patients did not exceed the MADRS cut-off but were currently being treated with antidepressants, possibly suggesting a corrected (upper limit) total prevalence of 33.6%. Females were more likely depressive than males (29.3% vs 22.4%). In both genders, depression risk was elevated 2- to 4-fold depending on HY stage. Overall, highest rates in non-demented patients were found in females at stages IV to V (53.7%, CI: 37.7-69.6). Demented patients were more likely to meet depression criteria than non-demented (up to 76.2%, 95% CI: 60.5-87.9). Depression symptom profiles for demented PD patients (as compared to non-demented) revealed no structural differences but consistently higher symptom scores. Neither age at onset of PD nor duration of disease were significantly linked with depression.
Conclusions: Depression rates are already substantially elevated at early PD stages, emphasizing the need for a thorough examination of mood disorders in all patients with PD. Depression is associated with PD severity and dementia but not with age, age at onset of PD, or disease duration. The differential associations with dementia and the statistical independence of dementia and depression also suggest that depression could not be regarded as a mere demoralisation syndrome.