Depression Linked To Elevated Parkinson's Risk
October 3, 2013

Depression Linked To Elevated Risk Of Parkinson’s Disease

Brett Smith for - Your Universe Online

Affecting about 1 in 500 individuals, Parkinson’s disease is a neurodegenerative condition marked by physical shaking or stiffness, and new research published in the journal Neurology has found a connection between depression and increased risk for the disease.

In the study, a team of Taiwanese researchers followed over 22,000 adults for a decade and discovered that people diagnosed with depression were over three times more likely to develop the neurodegenerative disorder than those who were not affected by the mental illness.

Depression has been linked to an increased risk for other physical diseases, including cancer and stroke, and while depression is more prevalent among Parkinson's patients than the general population, the researchers said it was unclear whether it is a cause or a symptom.

"Neurodegenerative disorders such as Parkinson's disease may initiate 10 to 20 years before they become symptomatic,” the study authors wrote, “therefore, we cannot obviate the possibility that depression is also an early symptom.”

The study cohort included more than 4,600 people who were diagnosed with clinical depression and almost 19,000 who were not. Sixty six people who were depressed, or 1.4 percent, would eventually be diagnosed with Parkinson's during the decade-long study period, compared with 97 of those without depression, or 0.5 percent. After researchers accounted for factors such as age, patients with depression were 3.2 times more likely to contract Parkinson's than those without.

The research team concluded that depression raises the long-term risk of Parkinson's by excluding the records of patients who were diagnosed with the neurological disorder just after their depression diagnosis. They added that increased age and having a form of depression which is difficult to treat both independently raised the risk of Parkinson's.

"Depression is linked in other studies to illnesses such as cancer and stroke,” said study author Dr. Albert C. Yang, from Taipei Veterans General Hospital in Taipei, Taiwan. “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,” he added.

Previous research has suggested that depression and Parkinson's are both rooted in bad synaptic connections in the brain, potentially meaning they share a common cause. Other studies have indicated a relationship between depression and chronic inflammation, which could increase the risk of Parkinson's.

Yang told CBS News that both diseases have an effect on neurotransmitters like dopamine and serotonin, which could be a factor. He added that antidepressant use in and of itself is not associated with increased risk, but people who are older than 65 and who have depression should speak to their doctor about their risk for Parkinson’s.

"The important message is that not all depression leads to Parkinson's," he said. "For elderly depression, it's also good to screen for any neurological disease as depression may be a red flag.”

According to the National Institute of Mental Health (NIMH), people with both conditions tend to have more movement problems and anxiety than those with either condition by itself.