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Could depression be an early manifestation of Parkinson’s?

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One of the most puzzling mysteries for scientists studying Parkinson’s disease has been its connection to depression.

Researchers have long observed that Parkinson's and depression go hand in hand. Both are associated with imbalances in brain chemistry, such as dopamine and serotonin levels. And a large percentage of people with Parkinson’s disease suffer from symptoms of depression at some point in their lives.

[Parkinson’s disease and depression often go hand in hand]

But there hasn't been any consensus about whether depression is a cause, a symptom or a consequence of the devastating effects of the neurodegenerative disease.

A new study published Wednesday in the journal Neurology sheds new light on this link, suggesting that depression may be the first manifestation of the disease before tremors or other physical issues appear. The study, which is significant because of its large size -- it looked at the entire population of Sweden over the age of 50 in 2005 which amounted to more than 500,000 people -- compared the rate of Parkinson's in those who did and did not suffer from depression. Their main finding: approximately 1 percent of those who had suffered depression developed Parkinson’s as compared with 0.4 percent of those who did not.

Peter Nordstrom, one of the researchers who worked on the paper, said the data seems to show that depression may be “a very early symptom” or even a risk factor for the disease. That doesn't mean that depression is a cause of the disease, but just that those with depression should be careful to be monitored for early symptoms of Parkinson's.