New research has found that the risk of developing dementia rises sharply with the number of mental health disorders a person has, with the odds jumping from twice as high for one disorder to 11 times as high for four or more.
The study, published in BMJ Mental Health, highlights the importance of recognizing psychiatric disorders not just as individual risks, but as powerful combined predictors of dementia.
Previous studies have shown that conditions such as depression, anxiety, and bipolar disorder each increase the risk of dementia on their own.
But until now, little was known about how the presence of multiple mental health disorders might influence the likelihood of developing dementia.
To explore this, researchers analyzed data from 3,688 patients aged 45 and older treated at Bicêtre Hospital’s psychiatry department in Paris between 2009 and 2023.
The patients had been diagnosed with one or more common psychiatric disorders, including depression, anxiety, psychosis, substance misuse, personality disorder, and bipolar disorder. All forms of dementia and cognitive impairment were considered.
The average age of participants was 67, with those who developed dementia averaging 70 years old and those without dementia averaging 66.
On average, dementia was diagnosed about 18 months after the first psychiatric disorder, although in some cases the gap stretched to more than a decade.
The analysis revealed that nearly three-quarters of the patients had one mental health disorder, while 22 percent had two, 6 percent had three, and just over 2 percent had four or more.
After adjusting for age, sex, and cardiovascular risk factors, the results showed a striking trend: the more psychiatric conditions a person had, the higher their likelihood of developing dementia.
Compared with patients who had one psychiatric disorder, those with two were twice as likely to develop dementia.
Those with three disorders were more than four times as likely, and those with four or more had an 11-fold increased risk. One of the strongest associations was seen in people with both mood and anxiety disorders, who faced a dementia risk of up to 90 percent.
The researchers noted that this effect appeared specific to dementia, since no link was found between multiple psychiatric conditions and another major illness, kidney failure.
This suggests that mental health problems may act as early warning signs of dementia rather than simply markers of general poor health.
As an observational study, the findings cannot prove cause and effect. The researchers caution that dementia diagnoses may have been delayed or misclassified, and that the study population—patients from one psychiatric department—may not reflect the wider population.
Even so, the results underscore the importance of monitoring people with multiple psychiatric disorders closely.
With new diagnostic tools such as blood and spinal fluid biomarkers and advanced brain scans becoming available, the researchers say early and accurate detection of dementia in high-risk patients could greatly improve treatment and care.
Source: KSR.
