The likelihood of developing dementia rises sharply with the number of co-existing psychiatric disorders, according to a French study published in BMJ Mental Health.
While individual psychiatric conditions such as depression, anxiety and bipolar disorder have previously been linked to a higher risk of dementia, this study explored the impact of having multiple co-existing psychiatric disorders.
How was the study conducted?
Researchers analysed data from 3,688 patients aged 45 and older who had been diagnosed with at least one common psychiatric disorder, including depression, anxiety, psychosis, substance misuse, personality disorder or bipolar disorder. They also assessed whether participants had any form of dementia or cognitive impairment.
Findings:
Most patients (71 per cent) had one psychiatric condition, but nearly 30 per cent had two or more. After adjusting for age, sex and cardiovascular risk factors, the study found a clear dose-response relationship: dementia risk increased significantly with each additional psychiatric disorder.
Compared to patients with only one psychiatric disorder, those with two were twice as likely to be diagnosed with dementia. The risk was four times higher for those with three mental health issues and 11 times greater for those with four or more. Notably, patients with both mood and anxiety disorders had a dementia risk of up to 90 per cent.
"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 authors concluded.