Several studies suggest there is a relationship between schizophrenia and dementia. People with a late onset of schizophrenia may have an increased likelihood of developing dementia.

A 2018 study emphasized that people with very late-onset schizophrenia (schizophrenia that appears for the first time after the age of 60) had a threefold increase in their risk of developing dementia. However, the exact nature of the relationship between schizophrenia and dementia is less clear. Researchers and doctors have considered late-onset and very late-onset schizophrenia as a rare but unique clinical entity for many years.

Researchers do not know whether schizophrenia is a risk factor for dementia, a cause of dementia, or whether one may help to predict the other. In fact, schizophrenia was once called “dementia praecox,” which means premature dementia.

However, schizophrenia has been characterized as having a decline in cognitive ability early in the course of the condition without much progression. In this case, the question is whether having schizophrenia increases the risk of a neurodegenerative disease such as dementia.

Psychosis, a collection of symptoms and a core feature of schizophrenia, could be an early warning sign of dementia. In some cases, dementia causes schizophrenia-like symptoms in people with no prior history of schizophrenia.

Keep reading to learn more about the link between dementia and schizophrenia, including how one may cause the other, some key differences, and some tips for management and prevention.

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A number of studies have found a link between having schizophrenia and later having a dementia diagnosis. For example, a 2018 meta-analysis reviewed six prior studies in which 1 in 25 participants had dementia. Researchers found a significant increase in the risk of developing dementia when a person also had schizophrenia.

Another 2018 study found a close correlation between very late onset schizophrenia and developing dementia. People with very late onset schizophrenia had a threefold increase in dementia rates.

It is unclear whether schizophrenia causes dementia, or if the two diseases share some other trait that makes them more likely to occur together. Researchers also do not know if treating schizophrenia reduces the risk of dementia.

Further complicating things is the fact that dementia and schizophrenia share many symptoms, including delusions, hallucinations, and behavioral changes. This is especially true for certain kinds of dementia, such as frontotemporal dementia, which tends to appear earlier in life and which may mimic schizophrenia symptoms.

Some people with dementia have symptoms of psychosis — a disconnection from reality even before they develop other symptoms. A 2017 paper emphasizes that people who receive a diagnosis of late-onset schizophrenia could actually be individuals who have dementia, but who have psychosis as part of their illness. This further illustrates the importance of a thorough medical evaluation that considers both diagnoses when individuals present with psychosis later in life.

Learn more about frontotemporal dementia here.

Diagnosing both schizophrenia and dementia can be challenging. The challenges increase when a person already has one of the two conditions.

There is no single definitive test for dementia. While tests can show that a person has declined in cognitive function, these tests cannot conclusively prove that dementia is the cause, or determine which type of dementia a person has. That said, the testing can help to determine which diagnosis is more or less likely.

Instead, doctors use a combination of tests, such as bloodwork and brain scans, to look for dementia markers, including signs of plaques in the brain. However, not all people with dementia develop brain signs of the disease, and some people with plaques or other symptoms do not have dementia.

Similarly, no single test can prove that a person has schizophrenia, and doctors do not use brain scans or blood tests to diagnose this condition. Rather, they base the diagnosis on symptoms such as delusions, hallucinations, socially unacceptable behavior, and a disconnection from reality.

Some of these symptoms are similar to dementia.

Certain types of dementia, especially frontotemporal dementia, are easy to confuse with schizophrenia. Frontotemporal dementia affects behavior and mental health, potentially causing aggression, impulse control, and hallucinations. It also tends to appear earlier in life than Alzheimer’s, making it even easier to mistake for schizophrenia.

Both schizophrenia and dementia affect thinking and behavior and may lead to false beliefs. Some important differences include:

  • Schizophrenia typically appears earlier in life than dementia, though there are exceptions, especially for very late-onset schizophrenia and early onset dementia.
  • Memory and thinking difficulties tend to be the earliest symptoms in most types of dementia. In schizophrenia, delusions and hallucinations may be more noticeable early in the disease.
  • Dementia is a progressive and terminal illness that steadily erodes brain function. While schizophrenia may get worse with time, it is not inevitably fatal nor progressive, and it does not typically affect daily functions such as bowel and bladder control.
  • There are many different types of dementia, each with their own unique early symptoms. Frontotemporal dementia, for example, more closely resembles schizophrenia in the early stages, while Alzheimer’s more typically attacks short-term memory.
  • People with dementia tend to develop other health problems, such as pneumonia and frequent infections, especially late in the course of the disease.

Both schizophrenia and dementia attack the brain, affecting a person’s ability to think clearly and engage in culturally typical behavior. Some important similarities include:

  • While there are different patterns to the average age of onset, both conditions can occur at any age.
  • The two conditions sometimes occur together.
  • Both can cause problems with memory, executive functioning, and behavior.
  • Both conditions may cause psychosis, which means that a person believes things that are untrue, or experiences things that are not there.
  • There is no cure for either condition, though both are treatable. Treatment for schizophrenia can help greatly reduce symptoms, while treatment for dementia tends to be ineffective as the disease progresses.
  • Both diseases can shorten a person’s life. Dementia is a terminal illness, and people with schizophrenia often live significantly shorter lives of 10–20 years less than people in the general population.
  • Both conditions are associated with other chronic medical illnesses, such as heart disease.

Dementia is a complex illness, with genetic, developmental, and environmental triggers. There is no strategy that can guarantee that a person will not develop dementia. However, some strategies can help reduce the risk:

  • Treat hearing loss as soon as possible, since hearing loss correlates with a higher risk of dementia.
  • Do not smoke, or quit smoking.
  • Get regular exercise, especially in midlife and beyond.
  • Remain mentally and socially active by spending time with friends, doing challenging activities, and avoiding isolation.
  • Eat a balanced diet that includes lots of whole grains, fruits, and vegetables.

A number of strategies can help a person manage symptoms of schizophrenia. They include:

  • Seeking care as soon as symptoms appear.
  • Taking antipsychotic medication, and talking with a doctor about whether additional medications might be appropriate.
  • Telling a doctor about any unwanted side effects, since additional drugs or changes in medication may help with these symptoms.
  • Seeking therapy with a psychotherapist who specializes in schizophrenia.
  • Finding support to get a job and integrate into the community. Support groups, occupational training, and peer mentoring may all help.

Schizophrenia can relapse, so it is important to know the signs that the diagnosis is getting worse. This makes it easier for a person to promptly seek care.

Both schizophrenia and dementia are chronic, incurable illnesses. While dementia is fatal, people can live long lives with schizophrenia, especially with the right medical care and social support.

Getting the right diagnosis can prove challenging, especially for people who develop symptoms later in life, or who have a long history of cognitive or mental health issues.

It is important to contact a neurologist with significant experience treating brain disorders to improve the odds of getting the right diagnosis.