ADHD Linked to More Than Fourfold Higher Risk of Dementia and Cognitive Decline in Major JAMA Psychiatry Study

PITTSBURGH — Adults with attention-deficit/hyperactivity disorder are significantly more likely to develop dementia or mild cognitive impairment later in life, according to a large U.S. study that also found genetic risk for ADHD was tied to cognitive decline even in people never diagnosed with the condition.

The research, led by scientists at the University of Pittsburgh School of Medicine, was published Oct. 7 in the journal JAMA Psychiatry. It analyzed health records and genetic data from more than 187,000 adults aged 50 and older enrolled in the National Institutes of Health's All of Us Research Program.

The researchers cautioned that the findings show an association, not proof that ADHD causes dementia.

"This doesn't prove that ADHD causes dementia," said senior author Dr. Tharick A. Pascoal, an associate professor of psychiatry and neurology at the University of Pittsburgh School of Medicine. He added that finding the same pattern independently in medical records and in participants' genes gives researchers greater confidence that the link is not simply an artifact of how ADHD is diagnosed.

What the study found

Of the 187,341 participants, 3,026, or 1.6%, had an ADHD diagnosis. The participants had an average age of about 56 when they entered the study, and 57% were women.

During follow-up, 6.7% of participants with ADHD developed mild cognitive impairment or dementia, compared with 3.4% of those without the disorder.

After adjusting for factors including age and sex, the researchers found ADHD was associated with a more than fourfold higher risk of cognitive impairment, with a hazard ratio of 4.60. Further adjustments for other health conditions, education and use of health care reduced the strength of the association but did not eliminate it.

Participants were followed for an average of about 10 years, using health record data stretching back as far as 1985.

Genetic evidence

The researchers also calculated a polygenic risk score for each participant, a measure of how many common genetic variants a person carries that are associated with ADHD, whether or not they were ever diagnosed.

Participants in the top fifth of genetic risk had a 35% higher risk of developing mild cognitive impairment or dementia than those in the bottom fifth. That association persisted after the researchers adjusted for medical and psychiatric conditions.

The genetic finding is significant because it addresses a key concern about earlier research: that the link might reflect diagnostic confusion rather than a genuine biological connection.

Ruling out misdiagnosis

One long-standing question in the field has been whether early signs of Alzheimer's disease or other forms of dementia, such as forgetfulness and difficulty concentrating, might sometimes be mistaken for ADHD in older adults. If so, an apparent link between the two conditions could be misleading.

To test this, the researchers required progressively longer gaps between an ADHD diagnosis and a later diagnosis of cognitive impairment. The elevated risk remained even when at least eight years separated the two diagnoses, according to a summary of the research released by the University of Pittsburgh.

Greater burden for patients

The study also found that among people who developed cognitive impairment, those who also had ADHD fared worse in several areas.

They had nearly twice the odds of reporting poor mental health, lower quality of life and reduced social satisfaction, and they used about 20% more health care services than people with cognitive impairment alone.

The authors said the findings support the need for targeted monitoring and integrated care for this group.

Caution over headline numbers

Some experts have urged caution in how the findings are interpreted. A psychiatrist writing for Psychology Today noted that because participants were relatively young at enrollment and followed for about a decade, dementia was uncommon during the study period. The association was strongest for mild cognitive impairment, while the estimate for dementia alone rested on far fewer cases and carried a much wider margin of error.

The same commentary pointed out that 10 of the 14 known modifiable risk factors for dementia, which include issues such as smoking, physical inactivity, hearing loss and social isolation, are elevated in people with ADHD. That raises the possibility that some of the increased risk may stem from health and lifestyle factors that are more common among people with the disorder.

Mild cognitive impairment involves noticeable problems with memory or thinking that are greater than expected with normal aging but do not severely interfere with daily life. While it can progress to dementia, not everyone with the condition goes on to develop it.

Building on earlier research

The findings are consistent with smaller studies conducted in Scandinavia and other parts of Europe that suggested adults with ADHD may face higher rates of neurodegenerative disease later in life. The new study is among the largest to examine the question in a U.S. population and among the first to combine clinical diagnoses with genetic data in the same individuals.

The Pittsburgh research group previously reported in 2022 that genetic risk for ADHD was linked to the buildup of amyloid and tau, proteins associated with Alzheimer's disease, in older adults who did not yet have cognitive symptoms.

ADHD is one of the most common neurodevelopmental disorders in children and often continues into adulthood. Symptoms in adults can include difficulty maintaining attention, staying organized and controlling impulsive behavior.

Open questions

The study did not determine why the association exists. Researchers have pointed to several questions for future study, including whether long-term use of stimulant medications commonly prescribed for ADHD affects later dementia risk, and whether better management of sleep, cardiovascular health and other lifestyle factors in midlife could reduce the risk.

The researchers emphasized that having ADHD does not mean a person will develop dementia. Most participants with ADHD in the study, more than 93%, did not develop cognitive impairment during the follow-up period.

The research was funded by the National Institute on Aging, the Alzheimer's Association, the U.K. National Institute for Health and Care Research and the European Research Executive Agency.