While a link has been made for some time between the degenerative disease and depression, this new research has prompted hopes that the causes behind the conditions can be found.

The new study was carried out using two groups of adults in the Taiwan National Health Insurance Research Database. Members of one group — over 56,000 individuals — were diagnosed with bipolar disorder between 2001 and 2009. The other — 225,000 individuals — had never been diagnosed with the disorder. No one in either cohort had received a Parkinson’s diagnosis and all the patients were over 20. Researchers ensured the two groups had similar ages, socioeconomic status, and other traits that might influence health.

The researchers followed up with all 278,000 people in 2011 to see how many had been subsequently diagnosed with Parkinson’s. They found that 0.7 percent of the patients with bipolar disorder ended up developing the disease — about 1 in 140. But for those without the disorder, the prevalence of Parkinson’s was about 1 in 1,000, or 0.1 percent.