Strong Link Between Number of Psychiatric Disorders and Dementia Risk

Recent research highlights a significant connection between the presence of multiple psychiatric disorders and the increased likelihood of developing dementia. Published in the open-access journal BMJ Mental Health, the study finds that the risk of dementia escalates with the number of co-occurring mental health conditions. Specifically, individuals with one psychiatric disorder have twice the risk, those with two are over twice as likely, and individuals with three or more disorders face an even higher probability.

The study analyzed data from 3,688 patients aged 45 and above, treated at Bicêtre Hospital's psychiatric department in Paris from 2009 to 2023. Common psychiatric diagnoses among participants included depression, anxiety, psychosis, substance misuse, personality disorders, and bipolar disorder. The average age of participants was 67, with those diagnosed with dementia averaging slightly older.

Findings revealed that nearly 71% of patients had a single psychiatric disorder, around 21.5% had two, 6% had three, and 2% had four or more. After adjusting for variables such as age, sex, and cardiovascular risk factors, the data showed a clear correlation: having two disorders doubled the chance of dementia, three disorders increased it by more than four times, and four or more disorders made individuals 11 times more likely to develop dementia.

Particularly, the combination of mood and anxiety disorders was associated with up to a 90% increase in dementia odds. The researchers suggest that these psychiatric conditions may serve as early warning signs rather than direct causes, as they did not find similar links with other diseases like renal failure. The study, however, is observational and does not establish causality. Limitations include potential diagnostic delays, misclassification, and the fact that data was sourced from a single psychiatric department, which may not represent broader populations.

The findings emphasize the importance of early detection and monitoring of psychiatric comorbidities, especially anxiety and mood disorders, to potentially reduce dementia risk. Advancements in biomarkers and neuroimaging offer promising tools for earlier diagnosis and improved management of high-risk individuals, possibly altering disease progression.

While these results deepen our understanding of the complex relationship between mental health and dementia, further research exploring causality and the impact of treatment is needed to develop targeted prevention strategies.

Source: https://medicalxpress.com/news/2025-09-odds-dementia-strongly-linked-mental.html