This study looks at the association between depression and Parkinson’s disease (PD) in a study group of 992 PD patients that were diagnosed after 2000. The diagnosis of depression and Parkinson’s Disease were self-reported. The conclusion drawn from this study is that a depression diagnosis before 2000 was in fact associated with higher levels of PD. However, it is important to note that this study does not explore other moderators such as poor health status. The authors conclude that depression may either share etiological factors with Parkinson’s Disease or that depression may in fact be an early symptom of PD. Further study into this topic is needed.
Full article: - http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2914462/