Adults With ADHD May Have a Higher Risk of Later Cognitive Issues

A new study of nearly 200,000 Americans has found that adults with attention-deficit/hyperactivity disorder (ADHD) were more likely than neurotypical peers to be diagnosed with mild cognitive impairment or dementia later in life.

Researchers also found that people with a higher genetic risk for ADHD, whether or not they were ever diagnosed, were more likely to develop thinking and memory issues.

Experts are quick to point out that the findings don’t prove ADHD causes dementia. But seeing the same pattern show up independently, in both medical records and in people’s genes, gives scientists greater confidence that the association is not simply because of how ADHD gets diagnosed, says senior author Tharick A. Pascoal, MD, PhD, an associate professor of psychiatry and neurology at the University of Pittsburgh in Pennsylvania. “Two different kinds of evidence are pointing in the same direction,” he says.

Data Came From the U.S. ‘All of Us’ Research Program

To investigate the connection between ADHD and later cognitive health, researchers turned to the National Institute of Health’s All of Us database, an ongoing project similar to the UK Biobank. Scientists gathered health records and genetic data from about 187,000 participants who were all age 50 or older. None had cognitive impairment or dementia at the start, and about 1.6 percent (3,026 people) had an ADHD diagnosis.

ADHD is a lifelong condition marked by ongoing trouble paying attention, hyperactivity and impulsive behavior, or both.

Mild cognitive impairment (MCI) describes noticeable changes in memory and thinking that go beyond typical aging, but it’s not usually bad enough to disrupt daily life; dementia entails more severe limitations.

Scientists searched for a connection among these conditions in two ways:

By checking whether adults with ADHD were later diagnosed with MCI or dementia more often than neurotypical adults
By checking whether adults with a higher genetic risk for ADHD, estimated from their DNA samples, were more likely to develop these conditions

People With ADHD Were More Likely to Be Diagnosed With Mild Cognitive Impairment or Dementia

After following participants for about 10 years, investigators found that the two groups did, in fact, develop cognitive issues at different rates. About 6.7 percent of people with ADHD were diagnosed with MCI or dementia, compared with 3.4 percent of people without ADHD — nearly double the rate.

When researchers compared people of the same age, sex, race, and ethnicity, ADHD was linked to more than four times the risk of cognitive issues. After accounting for other mental health conditions such as depression and anxiety (which were more common among the ADHD cohort), participants with ADHD had three times the risk.

This pattern also showed up in participants’ DNA: Adults who scored in the top fifth for genetic predisposition to ADHD had a 35 percent higher risk of MCI or dementia than people in the bottom fifth.

Earlier studies in Taiwan, Sweden, Israel, and Germany also found a higher risk of cognitive issues among people with ADHD, says a coauthor of the study, Douglas Teixeira Leffa, MD, PhD, a psychiatrist in Pittsburgh who recently completed his residency at the University of Pittsburgh Medical Center (UPMC).

“We’re replicating a pattern that’s been observed in other countries, now in a large U.S. sample, and adding genetic evidence on top of it,” says Dr. Leffa. “That combination gives us more confidence that ADHD deserves a closer look as a potential factor in cognitive aging,” he says.

Finally, the study also found that, among all participants who eventually developed MCI or dementia, those with ADHD had worse outcomes. Co-occurring ADHD was linked with poorer mental health, quality of life, and social satisfaction, as well as about 20 percent more healthcare visits in the following year. This pattern suggests ADHD may also shape how people experience cognitive impairment, says Leffa.