Introduction Depression is one of the most common non-motor symptoms of Parkinson's disease (PD). The prevalence rates vary widely according to the diagnostic criteria. However, in Korea, there are very few epidemiologic data concerning the prevalence of depression in PD. The aim of this study is to investigate the prevalence of depression and factors influencing depression in patients with PD.

Methods Newly diagnosed 252 consecutive PD patients were included and followed as part of an ongoing PD registry. PD was diagnosed according to the United Kingdom brain bank diagnostic criteria. 79 PD patients fulfilled the DSM-IV criteria for major depression. The UPDRS motor score was checked at the best “on” period to assess the clinical severity of PD. We compared the clinical data between depressive (DP, n=79) and non-depressive (NDP, n=173) groups.

Results The prevalence rate of depression in PD was 31.3% in this study. There was no difference in age (DP: 62.3±2.5, NDP: 59.8±2.7 yrs), age of disease onset (DP: 52.0±3.7 yrs, NDP: 54.7±3.8 yrs), UPDRS motor scores (DP: 36.2±5.6, NDP: 33.8±3.7) and Hoehn and Yahr stage (DP: 3.34±0.52, NDP: 2.91±0.63) between two groups.

Conclusion There was no significant difference in clinical features between DP and NDP groups in this study. These results suggest that depression in PD is not influenced the severity of motor symptoms and that non-dopaminergic neurotransmitters, such as norepinephrine and acetylcholine, at least associated with the pathophysiology of depression in PD.