Depression May Appear Years Before Parkinson’s and Lewy Body Dementia

Although there is currently no cure for Parkinson’s disease or Lewy body dementia, identifying and treating depression early may improve quality of life and support better care as these conditions progress.

A study published in General Psychiatry provides detailed long-term evidence that depression often appears before a diagnosis of Parkinson’s disease (PD) or Lewy body dementia (LBD) and can remain more common for years afterward.

Using Danish national health registers, researchers conducted a retrospective case–control study involving 17,711 people diagnosed with PD or LBD between 2007 and 2019. They compared these patients with individuals of similar age and sex who had other long-term illnesses, including rheumatoid arthritis, chronic kidney disease, and osteoporosis.

The analysis revealed a consistent pattern: depression was both more frequent and more likely to occur earlier among people who later developed PD or LBD than among those with other chronic conditions. In the years leading up to diagnosis, the risk of depression increased steadily and was highest in the three years immediately before diagnosis. After diagnosis, depression rates remained higher in PD and LBD patients than in the comparison groups.

Researchers noted that the findings could not be explained simply by the emotional burden of living with a long-term illness. Other chronic conditions that can also be disabling did not show the same sharp increase in depression. This suggests that depression may be linked to early neurodegenerative changes in the brain, rather than being solely a psychological response to declining health.

The pattern appeared strongest in Lewy body dementia. Depression rates were higher in LBD than in Parkinson’s disease both before and after diagnosis, which researchers suggested may be related to differences in disease progression and underlying brain chemistry.

“Following a diagnosis of PD or LBD, the persistent higher incidence of depression highlights the need for heightened clinical awareness and systematic screening for depressive symptoms in these patients,” said first author Christopher Rohde, adding that the overall conclusion remains clear: compared with other chronic conditions, PD and LBD are associated with a significantly increased risk of depression both before and after diagnosis.

The authors emphasized that the results do not mean everyone with depression will go on to develop Parkinson’s disease or dementia. Instead, they recommend increased awareness and closer monitoring when depression first appears in older adults.

While cures remain unavailable, addressing depression early may still help patients and their families by improving day-to-day wellbeing and supporting overall care as these diseases progress.