A new study of nearly 18,000 individuals diagnosed with Parkinson’s disease (PD) or Lewy body dementia (LBD) has revealed a significantly elevated risk of depression years before clinical diagnosis, suggesting a potential link between mood disorders and the earliest stages of neurodegenerative change. The research, published in General Psychiatry, indicates that depression is not simply a reaction to the challenges of living with a chronic illness, but may instead be an early symptom of these conditions.
Researchers from Denmark analyzed comprehensive national health registers, comparing individuals diagnosed with PD or LBD between 2007 and 2019 with a control group diagnosed with other long-term conditions like rheumatoid arthritis, chronic kidney disease, and osteoporosis. The study found that the risk of depression rose steadily in those who later received a PD or LBD diagnosis, peaking in the three years prior to their formal diagnosis. Even after diagnosis, rates of depression remained higher in the PD and LBD groups compared to the control groups.
“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 Christopher Rohde, the study’s first author. “our main conclusion—that PD/LBD are associated with a marked excess depression risk preceding and following diagnosis when compared with other chronic conditions—remains valid.”
The findings were particularly pronounced in individuals with Lewy body dementia. According to the Parkinson’s Foundation, DLB overlaps with Parkinson’s disease, making diagnosis challenging, and symptoms can include memory problems, tremor, rigidity, and hallucinations. The study suggests that the higher rates of depression observed in LBD may be related to differences in disease progression and brain chemistry compared to Parkinson’s disease.
Experts note that Lewy body dementia, along with Parkinson’s disease dementia, represents the second most common type of neurodegenerative dementia after Alzheimer’s disease. Both conditions are categorized as atypical parkinsonism, alongside Multiple System Atrophy (MSA), Progressive Supranuclear Palsy (PSP), and Corticobasal Syndrome (CBS). The presence of Lewy bodies – abnormal deposits of a protein called alpha-synuclein – is a hallmark of both DLB and Parkinson’s disease dementia, as noted by the Penn Memory Center.
While there are currently no curative treatments for Parkinson’s disease or Lewy body dementia, the study’s authors emphasize that early identification and treatment of depression could significantly improve the quality of life for patients. They caution, however, that the findings do not suggest that all individuals with depression will develop Parkinson’s or dementia, but rather advocate for increased vigilance and monitoring in older adults experiencing new-onset depression. The study does not offer guidance on specific treatments for depression in these populations, but highlights the need for further research into the relationship between mood disorders and neurodegenerative diseases.
