Having depression may increase your risk of developing Parkinson’s disease by up to three times, according to a new study.
The results could suggest that depression independently increases the risk of Parkinson’s, or that it is a symptom which affects patients very early in the course of the disease, researchers said.
It is also possible that using antidepressant drugs could raise the likelihood of patients developing the disease, they added in the Neurology journal.
Parkinson’s is a condition which causes the loss of nerve cells in the brain, leading to symptoms including shaking, slowness of movement and stiffness.
It is the second most common neurodegenerative disease after Alzheimer’s, affecting an estimated 127,000 people in the UK or about one in every 500.
Depression is known to raise the risk of a host of diseases including cancer and stroke, but although it is known to be more common among Parkinson’s patients than the general population, it remains unclear whether it is a cause or a symptom.
Researchers from Taipei Veterans General Hospital in Taiwan examined the medical records of 4,634 people who suffered from clinically diagnosed depression, and 18,544 who did not, over a ten-year period.
They found that 66 people with depression, or 1.42 per cent, went on to be diagnosed with Parkinson’s during the next decade compared with 97 of those without depression, or 0.52 per cent.
After other factors such as age were taken into account, patients with depression were found to be 3.24 times more likely to be diagnosed with Parkinson’s than those without.
Even when researchers excluded the records of patients who were diagnosed with Parkinson’s shortly after their depression diagnosis, the link was still apparent suggesting that depression raises the risk of Parkinson’s over the long term.
Greater age and having a form of depression which does not respond well to treatment both independently raised the risk of a Parkinson’s diagnosis, the scientists added.
Dr Albert Yang, who led the study, said: “Depression is linked in other studies to illnesses such as cancer and stroke. Our study suggests that depression may also be an independent risk factor for Parkinson’s disease.
“Many questions remain, including whether depression is an early symptom of Parkinson’s disease rather than an independent risk factor for the disease.”
Separate studies of depression and of Parkinson’s show that patients have similar connective failings in the brain, suggesting that the conditions could share a common cause.
Other research has shown that depression is linked to chronic inflammation, which in turn is thought to raise the risk of Parkinson’s.
The authors of the latest study said their findings suggested depression “may” independently raise the risk of Parkinson’s, but that they could not rule out the chance it is merely a symptom.
“Neurodegenerative disorders such as Parkinson’s disease may initiate 10 to 20 years before they become symptomatic … therefore, we cannot obviate the possibility that depression is also an early symptom,” they wrote.
This article first appeared on the The Telegraph on 2 October, 2013.