In a study from University College London, scientists found people with psychotic disorders such as schizophrenia are 2.5 times more likely than those without a psychotic disorder to eventually develop dementia.
They found that psychotic disorders may have a stronger link with dementia than other mental health disorders like depression or anxiety.
The study is the first high-quality systematic review looking at a range of psychotic disorders and their association with dementia risk.
Schizophrenia and other related psychotic disorders are severe illnesses that involve symptoms such as hallucinations and delusions, and social withdrawal.
Many people also experience impairments in cognitive and functional skills.
In the study, the researchers analyzed evidence from 11 studies from nine countries on four continents, which included close to 13 million participants in total.
They found that across multiple different psychotic disorders, regardless of the age at which someone first developed their mental illness, there was a higher risk of dementia later in life.
Some studies included people diagnosed with psychotic disorders while young adults, with follow-up periods of multiple decades.
They also found that people who have had a psychotic disorder tend to be younger than average at dementia diagnosis, with two studies finding that people with psychotic disorders were much more likely to be diagnosed with dementia while still in their 60s.
The findings add to the list of modifiable risk factors for dementia.
The researchers have previously found that four in 10 dementia cases could be prevented or delayed by targeting risk factors from across the lifespan.
These latest findings suggest that psychotic disorders have the strongest association with dementia risk.
The researchers were not able to confirm the cause of the association, whether it is due to the mental illness itself, or perhaps because psychotic disorders increase the likelihood of conditions that in turn increase the risk of dementia.
Some of the association may be because psychotic symptoms could be early markers of dementia for some people, but the fact that some of the studies had very long follow-up periods and included people experiencing psychosis at young ages suggests this is not the only explanation.
If you care about dementia, please read studies about three biggest risk factors for the dementia risk, and a key to activating ‘fountain of youth’ in brain.
For more information about brain health, please see recent studies about a new way to predict dementia before symptoms appear, and results showing high blood pressure may lower dementia risk for some old adults.
The study was conducted by Dr. Jean Stafford et al and published in Psychological Medicine.
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