A large scale study conducted in Sweden has found a link between depression and Parkinson’s disease, leading the researchers to believe that depression may be an early symptom of or risk factor for Parkinson’s. The findings were published in Neurology.
Scientists at Umeå University studied 140,688 Swedish citizens age 50 or older who were diagnosed with depression from 1987 to 2012. They matched each of these participants with three control participants of the same sex and birth year who had not been diagnosed with depression, totalling 421,718 control participants.
They followed the participants for up to 26 years and found that 1,485 people – or 1.1% of participants – with depression developed Parkinson’s disease during this time. Of those who were not diagnosed with depression, 1,775 of them developed Parkinson’s – only 0.4% of the control participants.
About 15-25 years after the study began, people who were diagnosed with depression were approximately 50% more likely to develop Parkinson’s disease.
The team also looked at siblings and other conditions that could influence the link between depression and Parkinson’s. They found no link between one sibling having depression and the other having Parkinson’s disease despite potential genetic or early environmental factors. This also held true when traumatic brain injury, stroke and alcohol and drug abuse were factored in – the link between depression and Parkinson’s was not altered by any of these conditions.