A large study from Spain has found that people living with severe mental illness were much more likely to have dementia across adulthood.
They also had a higher risk of stroke, with the difference especially noticeable among younger and middle-aged adults.
The findings are important because dementia and stroke are often thought of mainly as diseases of older age.
The new research suggests that doctors may need to pay attention to brain, heart and blood vessel health much earlier in people with serious psychiatric conditions.
Researchers examined health records from nearly 700,000 people in Catalonia, Spain. About 177,000 had been diagnosed with schizophrenia, bipolar disorder or major depression, while roughly 517,000 did not have a recorded psychiatric diagnosis.
These conditions can have major effects on mood, thinking, behavior and everyday life. They can also be linked with physical health problems, but researchers are still working to understand why some medical conditions occur more often in people with severe mental illness.
The team compared rates of dementia and stroke among people from 20 to 99 years old. They found that severe mental illness was associated with dementia in every age group they examined.
The difference was particularly striking among adults aged 30 to 39. People with severe mental illness in this age group had more than 20 times the odds of having dementia compared with people without a psychiatric diagnosis.
However, the researchers stressed that dementia was still uncommon among people in their thirties. About 550 out of every 100,000 people with severe mental illness had dementia, compared with around 24 out of every 100,000 people without severe mental illness.
This distinction matters because a very large increase in relative risk can sound frightening even when the actual number of affected people remains small. In the study, dementia affected about 0.55% of people with severe mental illness aged 30 to 39, compared with about 0.02% of those without a psychiatric diagnosis.
The gap became smaller with age but did not disappear. Among adults aged 80 to 89, people with severe mental illness still had roughly four times the odds of dementia.
Dementia is not a single disease. It describes a group of conditions that cause serious and continuing problems with memory, thinking, judgment and the ability to manage normal daily activities.
Alzheimer’s disease is the most common cause, but dementia can also result from damage to blood vessels in the brain and from other diseases. Age is the strongest known risk factor, which is why dementia in younger adults is unusual.
The researchers also examined stroke. A stroke happens when part of the brain suddenly loses its normal blood supply or when a blood vessel in the brain bursts.
An ischemic stroke, the most common type, occurs when a clot blocks blood flow to part of the brain. Without enough oxygen, brain cells can begin to die quickly, making emergency medical treatment essential.
The study found that the association between severe mental illness and stroke was particularly strong in early and middle adulthood. Adults aged 40 to 49 with severe mental illness had nearly three times the odds of ischemic stroke compared with people without a psychiatric diagnosis.
There are several possible explanations for these differences, but the study was not designed to determine the cause. People with serious mental illness can experience higher rates of smoking, diabetes, high blood pressure, poor sleep and other factors that may affect brain and heart health.
Some people may also have difficulty accessing regular medical care or maintaining healthy routines because of symptoms, financial pressures or social disadvantage. Certain psychiatric medicines can also affect weight, blood sugar or other parts of physical health, although they can be essential and highly beneficial for controlling mental illness.
Biological factors may contribute as well. Scientists are investigating whether inflammation, stress responses and changes in blood vessels or brain function could help connect psychiatric illness with later physical and cognitive problems.
The researchers say the findings support a whole-person approach to treatment. Mental health care could include regular attention to blood pressure, cholesterol, blood sugar, smoking, exercise and other factors that influence stroke and dementia risk.
Checking thinking and memory may also be useful when there are concerns about cognitive decline. Cognitive problems can occur in schizophrenia, bipolar disorder and major depression even when a person’s main psychiatric symptoms are relatively stable.
Professor Kamilla Miskowiak of the University of Copenhagen, who was not involved in the study, said cognitive and brain health should be important treatment targets for people with severe mental illness. She also emphasized identifying health risks that can potentially be changed.
There is an important limitation to the research. The study was cross-sectional, meaning it examined health records at a particular point rather than following the same people for many years.
Because of this design, researchers cannot conclude that severe mental illness directly causes dementia or stroke. The study shows a strong association, but other medical, social, lifestyle and treatment-related factors may help explain the differences.
The researchers now want to conduct studies that follow patients over time. This could help determine when the increased risks begin and which factors are most responsible.
The research was led by scientists including Dr. Michele De Prisco of Hospital Clínic-IDIBAPS and the University of Barcelona. The findings were published in the journal European Neuropsychopharmacology.
Overall, the study’s greatest strength is its very large sample and its ability to compare risks across many different ages. Its main weakness is that it cannot establish cause and effect, so the dramatic differences in younger adults should not be interpreted as proof that psychiatric illness itself causes early dementia.
The findings nevertheless carry an important message for health care. Serious mental illness can affect much more than emotional wellbeing, and regular attention to physical, cardiovascular and cognitive health may need to begin much earlier than is often assumed.
Source: University of Barcelona.
