People with depression may be more likely to develop the movement disorder Parkinson's disease, according to new research published in Neurology. "link between depression and Parkinson's disease over a timespan of more than 2 decades, so depression may be a very early symptom of Parkinson's disease or a risk factor for the disease," says study co-author Prof. Peter Nordström, at Umeå University in Sweden. Parkinson's disease is a progressive disorder of the nervous system that affects how a person moves, including how they speak and write. As well as problems with movement, Parkinson's disease can also cause cognitive problems, neurobehavioral problems and sensory difficulties. The authors of the study state that depression is more common in patients with Parkinson's disease than in members of the general population. The mood disorder has a major influence on health-related quality of life and could also be involved in more rapid deterioration of cognitive and motor functions. However, few studies have investigated this association for periods of longer than 10 years, with any long-term findings so far inconclusive. For the study, the researchers used a cohort consisting of all Swedish citizens aged 50 years and above as of December 31st, 2005. From this group, they then took the 140,688 people diagnosed with depression between 1987 and 2012. These individuals were each matched with three control participants (a total of 421,718 controls) of the same age and sex who had not been diagnosed with depression. The participants were then followed for up to 26 years. A total of 1,485 people with depression (1.1%) developed Parkinson's disease during this time, compared with 1,775 of those who did not have depression (0.4%). On average, Parkinson's disease was diagnosed 4.5 years after the beginning of the study, with the likelihood of the disorder developing decreasing over time."