Risk of dementia increases with co-existing mental health conditions

The risk of developing dementia increases with a number of co-existing mental health disorders, French researchers have reported.

A study published in BMJ Mental Health found the odds of dementia was twice as high with two mental health disorders and 11 times as high for those with four or more, compared to those with one.

It appears that the combination of concurrent mood and anxiety disorders was particularly linked to a heightened risk, they concluded.

Other research has identified individual associations with psychiatric disorders, such as depression, anxiety, and bipolar disorder and the risk of developing dementia but it has not looked at a cumulative pattern of having multiple conditions.

The study used data from 3,688 patients aged at least 45 and diagnosed with one or more of depression, anxiety, psychosis, substance misuse, personality disorder and bipolar disorder between August 2009 and October 2023.

They then looked at the development of all types of dementia and cognitive impairment.

Around 70% of the patients had one psychiatric disorder with the numbers falling with each additional condition and only 2% having four or more.

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

Those with three disorders, were more than four times as likely to develop dementia as those with one, the team found.

The combination of concurrent mood and anxiety disorders was linked to odds of dementia of up to 90%.

The paper said: ‘Patients with co-occurrence of mood and anxiety disorders had a mean posterior probability from 48% (34.1–62.2) up to 89.6% (76.8–98.6) of dementia.’

As a unique finding, it could be that concurrent psychiatric disorders are early warning signs of dementia.

This is supported by further in-depth analysis testing the potential effects on the likelihood of other disease – which they did with renal failure – failed to show any link, the researchers explained.

No firm conclusions can be drawn about cause and effect from the data, the researchers stressed, and it should be noted the patient data was from one psychiatric department.

There was also a lack of information on socioeconomic status, family history, duration of psychiatric disorder, treatment and brain scans.

But they concluded: ‘The findings of this study highlight the strong association between the co-occurrence of psychiatric disorders and an increased posterior probability of developing dementia, particularly for patterns with anxiety and mood disorders.’ 

Methods to identify earlier dementia diagnoses, such as the development of biomarkers in blood and cerebrospinal fluid and PET scans, could be used in clinical practice for high-risk individuals, they added. 

‘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.’

Earlier this year researchers reported that depression in late-life was associated with an increased risk of dementia.

Other work has has suggested that people with both pre-diabetes and depression are nearly three times more at risk of developing dementia in later life.