Dementia increases sharply with the number of comorbid psychiatric disorders, with mood and anxiety disorders posing the greatest risk, new research showed.

Compared to individuals with a single psychiatric disorder, those with two were twice as likely to be diagnosed with dementia, whereas those with three disorders were more than four times as likely.

Four or more psychiatric disorders were associated with an 11-fold increased likelihood of developing dementia. In addition, the combination of mood and anxiety disorders poses the greatest risk, with up to a 90% probability of dementia in some subgroups.

“These findings highlight the need for targeted dementia screening and preventive actions in patients developing more than one psychiatric disorder, particularly those with both anxiety and mood disorders,” the investigators, led by Edouard Baudouin, MD, Department of Geriatrics, Paul Brousse Hospital, Villejuif, France, wrote.

They noted that psychiatric disorders may serve as “early markers” of dementia, given the short average delay of just 1.6 years between the first psychiatric disorder diagnosis and dementia diagnosis in the cohort.

The study was published online on September 9 in BMJ Mental Health.

Risk Multiplier

The global burden of dementia is growing, with the World Health Organization estimating 10 million new cases each year.

Psychiatric disorders, such as depression, anxiety, and bipolar disorder, have been individually associated with an increased risk for dementia, but how co-occurring psychiatric disorders affect dementia risk remains unclear.

To investigate, researchers analyzed data from 2009-2023 on 3688 adults aged 45 years or older (mean age, 67 years) with at least one psychiatric disorder (depression, anxiety, psychotic, substance use, personality, or bipolar disorders).

Nearly 71% of the patients had one psychiatric disorder, about 22% had two psychiatric disorders, 6% had three and 2% had four or more.

After adjusting for age, sex, and cardiovascular risk factors, the odds of dementia rose in tandem with the number of psychiatric disorders.

A total of 653 individuals (18%) developed dementia. And the average delay between diagnosis of the first psychiatric disorder and dementia diagnosis was 18 months but ranged from 7 to 13 years.

The adjusted odds ratio for dementia increased from 2.3 for two disorders, to 4.6 for three disorders, to 11.1 for four or more disorders compared with those with one psychiatric disorder.

In subgroup analyses evaluating different patterns of psychiatric co-occurrence associated with dementia, patients with both depressive and anxiety disorders had a probability of dementia ranging from 48% for those with co-occurring depressive, anxiety, and personality disorders to 90% for those with comorbid depressive, anxiety, psychotic, and substance use disorders.

Screen and Treat

The researchers noted that recent advances in diagnosing dementia, including blood biomarkers and imaging, permit earlier and more accurate detection of dementia.

“Integrating these tools into clinical practice for high-risk individuals, especially those with specific psychiatric comorbidities identified in this study, could significantly enhance their care management, given the recent advancements in dementia treatment,” they concluded.

Reached for comment, Kay Khaing, MMed, with The University of Newcastle, Callaghan, Australia, said this study “adds strong evidence that anxiety is the risk factor for dementia.”

In a recent study of adults aged 55-85 years, Khaing and colleagues found that both chronic and new-onset anxiety was linked to about a threefold increased risk for dementia.

“Therefore, psychiatric disorders — and more importantly mood/anxiety disorders — should be screened in the primary care setting in order to timely manage these issues to prevent dementia in later life,” Khaing told Medscape Medical News.

Also providing perspective, Badr Ratnakaran, MBBS, chair of the American Psychiatric Association Council on Geriatric Psychiatry, said this study is “the latest evidence of the association of psychiatric disorders with dementia.”

“The association between psychiatric disorders and dementia has been known for a long time and is universal with studies conducted in various countries,” Ratnakaran told Medscape Medical News.

He noted that there are many reasons considered for the association, “including the relationship of inflammation and stress in psychiatric disorders and dementia, and increased risk for cardiovascular disorders and poor health behaviors like lack of exercise and substance use.”

Ratnakaran also emphasized the importance of screening for mood and anxiety disorders and “timely interventions at the level of primary care. This is important due to barriers to access to psychiatric care, and improved outcomes have been shown for behavioral interventions at the primary care level,” he said.

This study had no specific funding. Baudouin, Khaing, and Ratnakaran had no relevant conflicts of interest.