Depression and anxiety are twice as common in people newly-diagnosed with Parkinson's disease compared with the general population, new US research suggests.
Writing after the recent Robin Williams' suicide, researchers say depression increases in frequency in Parkinson's patients and is often left untreated. Previous research has suggested that the disease's impact on the brain can be a trigger for depression.
Lead researcher Dr Daniel Weintraub, from the Perelman School of Medicine at the University of Pennsylvania, said depression in Parkinson's disease was under-recognised.
"There are psychological reasons why people who have been diagnosed with a neuro-degenerative disease like Parkinson's can become depressed, but their brain pathways are also affected by the disease and these are closely associated with mood."
His team examined 423 newly-diagnosed Parkinson's patients and tracked their mental health over two years. At the outset, 14% of patients with Parkinson's disease were found to have depression, compared with 6.6% of a group of healthy volunteers.
During the follow-up, there was a small rise in the frequency and severity of depression in the group with Parkinson's, while in the control group a decrease was noted.
At the start of the study, 16% of patients with Parkinson's were taking an anti-depressant, and this increased significantly to 25% two years later. But 65-72% of patients who screened positive for depression were still not being treated with medication, the study concluded.
Because of the range of possible causes, Parkinson's UK says it is important that patients speak to their healthcare professional if they are worried about their symptoms. Depression can also be a side effect of Parkinson's drugs.