Depression Appears To Be An Early Sign Of Parkinson's Disease And Dementia

This study showed that depression is much more common in people with Parkinson's disease and Lewy body dementia than in people with other chronic diseases. Most importantly, this elevated risk appears several years before the official diagnosis, suggesting that depression may be an early sign of the brain changes associated with these diseases. These findings highlight the importance of carefully investigating episodes of depression in older adults and providing appropriate treatment from the early stages.

Depression is very common in people with Parkinson's disease and Lewy body dementia. It is estimated that between thirty and forty percent of patients with these diseases develop depression at some point.

In the case of Parkinson's disease, the presence of depression is associated with significant changes in the brain, such as a reduction in the volume of some brain areas, as well as faster disease progression, greater impairment of memory and thinking, increased disability in daily activities, a higher risk of suicide, and increased overall mortality.

Both Parkinson's disease and Lewy body dementia are neurodegenerative diseases, meaning they cause a progressive deterioration of brain cells over time. Many researchers believe that these progressive brain changes may be directly related to the onset of depression.

Previous studies reinforce this idea by showing that the risk of developing depression is already higher even before an official diagnosis of Parkinson's disease. In a recent study, for example, it was observed that people who later received a diagnosis of Parkinson's disease experienced depression more frequently up to ten years before diagnosis, compared to people without the disease. This suggests that early, still silent, brain changes can trigger depressive symptoms long before the disease is clinically recognized.

Another possible explanation is that the early signs of Parkinson's disease or Lewy body dementia, even if not yet diagnosed, cause physical, cognitive, and emotional difficulties that lead to depression.

This situation also occurs in other chronic diseases, such as rheumatoid arthritis and chronic kidney disease, where the limitations imposed by the disease can contribute to the development of depressive symptoms, even without direct brain involvement.

The aim of this study was to accurately measure how many people develop depression before and after a diagnosis of Parkinson's disease and Lewy body dementia, and to compare these numbers with those observed in other chronic diseases. To do this, the researchers used data from people with rheumatoid arthritis and chronic kidney disease, which are diseases that cause a significant physical impact but do not directly affect the nervous system.

These diseases served as a type of active comparison. In addition, osteoporosis was used as an additional comparison, as it tends to cause less disability but still requires regular medical follow-up, which helps to reduce distortions related to access to health services.

The logic behind this comparison was simple: if depression appeared much more frequently in people with Parkinson's disease and Lewy body dementia, especially before diagnosis, this would indicate that depression may be an early sign of the brain changes that lead to these diseases.

This finding would also reinforce the importance of paying special attention to cases of depression that arise in old age, as they may indicate an increased risk for the development of these neurodegenerative conditions.

To conduct the study, researchers analyzed health records from Denmark, a country that maintains very comprehensive medical databases. All individuals diagnosed with Parkinson's disease or Lewy body dementia between 2007 and 2019 were identified.

Each of these individuals was compared with up to three other people of the same age, sex, and diagnosis period, but who had rheumatoid arthritis, chronic kidney disease, or osteoporosis. In this way, the groups were as similar as possible, except for the type of disease.

The researchers then analyzed how many of these individuals developed depression over time. The presence of depression was assessed from up to ten years before the diagnosis of the primary illness to ten years after. To compare the risk of developing depression among the different groups, a statistical method was used that allows tracking events over time and calculating the probability of a given outcome occurring, taking into account individual differences among the participants.

In total, the study included more than seventeen thousand people with Parkinson's disease or Lewy body dementia. The average age of these patients was approximately seventy-five years, and about forty percent were women. These participants were compared with tens of thousands of people with rheumatoid arthritis, chronic kidney disease, and osteoporosis.

The results showed that, from seven to eight years before diagnosis to about five years after, people with Parkinson's disease and Lewy body dementia had a consistently higher risk of developing depression than all comparison groups.

Risk rate of incident depression before and after diagnosis of Parkinson's disease, Lewy body dementia, rheumatoid arthritis, chronic kidney disease, and osteoporosis. '0' represents the date of diagnosis of Parkinson's disease, Lewy body dementia, rheumatoid arthritis, chronic kidney disease, and osteoporosis. Credit: Christopher Rohde, Martin Langeskov-Christensen, Lene Bastrup Jørgensen, Per Borghammer, Søren Dinesen Østergaard.

These results indicate that depression may be one of the first signs of the brain changes that later lead to Parkinson's disease and Lewy body dementia. Furthermore, they reinforce the importance of recognizing and treating depression in older people, not only to improve quality of life but also as a way to increase vigilance for potential neurodegenerative diseases.

Throughout life, people often create mental images of who they want to become in the future, such as wanting to be a confident, accomplished, or professionally successful person. These identity goals function as internal guides that direct choices and behaviors over time.

However, when chronic and neurodegenerative diseases arise, these future plans can be interrupted or profoundly altered, which can contribute to feelings of loss, frustration, and depression, especially when the individual realizes they will not be able to live the life they envisioned.

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Depression preceding and following the diagnosis of Parkinson’s disease and Lewy body dementia

Christopher Rohde, Martin Langeskov-Christensen, Lene Bastrup Jørgensen, Per Borghammer, and Søren Dinesen Østergaard

General Psychiatry. 3 December 2025.DOI: 10.1136/gpsych-2025-102405

Abstract:

Depression is a common comorbidity in Parkinson’s disease (PD) and Lewy body dementia (LBD). However, studies examining the rate of incident depression in the period preceding and following the diagnosis of PD and LBD are lacking in the literature. To quantify the incidence of depression in the period preceding and following the diagnosis of PD and LBD. We conducted a retrospective case-control study. Specifically, we used Danish registers to identify all patients with a diagnosis of PD or LBD in the period from 2007 to 2019. These patients were matched by age, calendar year of diagnosis and sex with up to three patients diagnosed with rheumatoid arthritis (RA), chronic kidney disease (CKD) or osteoporosis, respectively. The outcome was incident depression. The incidence of depression was assessed for up to 10 years before and up to 10 years after the diagnosis of PD or LBD. Hazard rates of incident depression for patients with PD or LBD, both before and after diagnosis, were compared with those for patients with RA, CKD or osteoporosis using a Cox-proportional hazards model. We identified 17 711 patients with PD or LBD. Their median age was 74.98 (68.10–80.85) years, and 39.92% were females. These patients were matched to 19 556, 40 842 and 47 809 patients with RA, CKD and osteoporosis, respectively. From 7 to 8 years before diagnosis to 5 years after diagnosis, patients with PD and LBD consistently had higher hazard rates of incident depression than all comparator groups. These findings are compatible with depression being an early manifestation of the neurodegenerative changes eventually leading to PD and LBD and imply that incident depression at a late age should raise awareness of potential PD and LBD.