Study Rationale:
Mood disorders are common in people with Parkinson’s disease (PD) and, in many cases, precede motor symptoms and diagnosis by years. The relationship between bipolar disorder and PD is particularly intriguing as some of the symptoms (e.g., depression) and underlying mechanisms (inflammation, oxidative stress) may be shared between both conditions. Bipolar disorder that occurs before PD diagnosis could represent an early stage of PD.
Hypothesis:
We hypothesize that people with bipolar disorder have an increased risk of subsequently developing PD when compared to people without bipolar disorder, and that more severe disease such as more hospitalizations and worse manic episodes, further increases the risk.
Study Design:
We plan to study the relationship between bipolar disorder and PD in two large, well-characterized populations: the Parkinson’s Progression Markers Initiative (PPMI) and the Kaiser Permanente Northern California health system (KPNC). In each population, we will determine the risk of developing PD after people are diagnosed with bipolar disorder and describe the clinical features of each condition that are most associated with the other. We will also explore how genetic variants and medications affect this relationship. Finally, we will evaluate whether people with PD who have had bipolar disorder have different clinical outcomes.
Impact on Diagnosis/Treatment of Parkinson’s Disease:
Understanding this relationship may allow us to better identify those at risk of PD. This is a critical need that will help scientists develop and implement therapies to prevent or slow PD progression. The results of this study may also identify shared mechanisms or risk factors between bipolar disorder and PD. This knowledge could lead to new treatments.
Next Steps for Development:
The results of this study could immediately improve our ability to identify people at risk of PD and enhance our understanding of the underlying mechanisms. Scientists believe that the earlier we intervene in the underlying disease process, the more effective new therapies are likely to be. Potentially modifiable risk factors that we identify could lead to clinical trials focused on trying to prevent PD in people with bipolar disorder.