A study of nearly 700,000 people found an association between severe mental illness and dementia across every age group studied.
Adults ages 30 to 39 with severe mental illness had more than 20 times the odds of dementia compared with those without a psychiatric diagnosis.
Stroke risk was also higher among people with severe mental illness, with the strongest association appearing among adults ages 40 to 49.
Dementia and stroke are often thought of as conditions that primarily affect older adults. But new research suggests that, among people with severe mental illness, the connection with these neurological conditions may show up much earlier in adulthood.
The study, published in European Neuropsychopharmacology, looked at severe mental illnesses including schizophrenia-spectrum disorders, major depressive disorder and bipolar disorder. Researchers found that people with these conditions had higher odds of dementia across every age group examined, from ages 20 to 29 through 90 to 99.
The researchers also found an association with ischemic stroke — the most common type of stroke, which happens when a blood vessel supplying the brain becomes blocked. The relationship was particularly noticeable during early and middle adulthood.
How researchers conducted the study
For the study, researchers analyzed health records from the PADRIS-PRESTO cohort, which draws from primary and specialized care records in Catalonia, Spain.
The final analysis included 694,086 adults. Of those, 176,870 had a lifetime diagnosis of severe mental illness, while 517,216 did not have a psychiatric diagnosis. Researchers divided participants into 10-year age groups and compared the prevalence of dementia and ischemic stroke between the two groups.
They then used statistical models to calculate age-specific odds of dementia and stroke. The models also accounted for socioeconomic status and the overall burden of other medical conditions. Researchers examined the three major severe mental illness categories separately as well.
Importantly, this was a cross-sectional study, meaning it provides a snapshot of the relationship between these conditions rather than following people over time. As a result, the findings show an association — they do not establish that severe mental illness causes dementia or stroke.
What the findings mean for consumers
The numbers were particularly striking among younger adults. Between ages 30 and 39, people with severe mental illness had more than 20 times the odds of having dementia compared with controls. Still, dementia was uncommon in this age group overall: It affected 0.55% of people with severe mental illness compared with 0.02% of controls.
“Although dementia remains rare in that 30 to 39 age group overall, the size of the difference associated with mental illness was notable,” researcher Dr. Michele De Prisco said in a news release. “For every 100,000 people without a severe mental illness, about 24 had dementia at ages 30-39, compared with about 550 among those with a severe mental illness"
The association remained in older adults, although the relative difference became smaller as dementia became more common overall. For ischemic stroke, the strongest association appeared among people ages 40 to 49, who had nearly three times the odds of stroke compared with controls.
“These findings reinforce the need to think about severe mental illness as a whole-person health issue, not only a mental health diagnosis,” Dr. De Prisco “What we are seeing is that risks linked to subsequent dementia and stroke may appear much earlier in life than many people expect, which means prevention, monitoring, and coordinated care should also begin earlier”.