Adults With ADHD May Be 3 Times More Likely to Develop Dementia, Study Shows

Adults with attention-deficit/hyperactivity disorder (ADHD) are almost three times more likely to develop dementia compared to adults who do not have ADHD, according to a new study.

The new research, published last week in JAMA Network Open, followed more than 109,000 older adults in Israel to better understand if those with ADHD were at increased risk for dementia, including Alzheimer’s disease.

Researchers noted that dementia is common in the elderly, yet the underlying etiology is not well understood, but some previous research has suggested a link between ADHD and neurodegenerative disease. 

“We were interested in understanding how brain conditions that may affect cognitive functioning, including ADHD, may contribute to old age dementia,” Michal Schnaider Beeri, PhD, director of the Herbert and Jacqueline Krieger Klein Alzheimer’s Research Center, a member of the Brain Health Institute at Rutgers University, and a co-author of the study, told Health.

“Understanding such links may help us both focus prevention strategies on high-risk populations and shed light into novel mechanisms connecting between the two conditions,” she said.

Dementia is not a specific disease, but rather a group of symptoms characterized by dysfunction in daily life due to cognitive impairment.

Dementia ranks as a leading cause of disability and mortality, with 6.7 million U.S. adults aged 65 or older estimated to have the condition in 2023. That number is expected to increase to 13.8 million by 2060.

Although ADHD is generally defined as a neuro-developmental disorder, its symptoms can include: not paying close attention to details, interrupting or intruding on others, and being unable to engage quietly in leisure activities.

Beeri explained that people with ADHD, particularly cases that are untreated or not managed correctly, may struggle with impulse control, which can lead to unhealthy lifestyle choices.

“This can include poor dietary habits and lack of exercise, obesity and hypertension, all of which contribute to dementia risk," she said. "In addition, it is conceivable that the neurobiology of ADHD contributes to compromised brain and cognitive reserve, increasing dementia risk in old age.”

Connecting Dementia and ADHD

To better understand the connection between dementia and ADHD, researchers used data from a national cohort study of more than 109,000 people born between 1933 and 1952 and followed from 2003 to 2020.

None of the participants had a diagnosis of ADHD or dementia when monitoring began; roughly half were male and half were female.

Researchers found that even when other risk factors for dementia, like cardiovascular disease, adults with ADHD had a 2.77-fold increased risk of developing dementia.

During follow-up, 730 participants (0.7%) received a diagnosis of adult ADHD, and over 7,700 (7%) received a diagnosis of dementia. Dementia occurred among 13% of adults with ADHD and 7% without adult ADHD.

However, finding why adult ADHD and dementia seem to be connected was something researchers could not find.

“The exact causes for the relation between adult ADHD and dementia are unknown,” Sven Sandin, PhD, associate professor of psychiatry at Icahn School of Medicine at Mount Sinai and a co-author of the study, told Health.

“It is possible that some of the genetic causes of ADHD and the genetic causes of dementia are the same, and therefore there are similar genetic pathways to both disorders,” he said.

Other studies have shown similar findings.

A 2022 study reported that people with ADHD were at a higher risk for dementia and mild cognitive impairment. That risk, however, dropped when the findings were adjusted for psychiatric disorders like depression, anxiety, substance abuse use disorder, and bipolar disorder.

And, a 2023 study found ADHD as a less common, but possible contributor to some cases of cognitive impairment like dementia.

How Childhood Impacts Adult ADHD

While childhood ADHD and adult ADHD are intrinsically linked, there are often experiential differences based on when someone is diagnosed with ADHD.

Previous research has reported that 5% of children with ADHD meet ADHD criteria in adulthood, making up 3% of all adult ADHD cases.

Studies have also shown that child and adult ADHD present different social, psychological, and genetic profiles, and little is still known about adult ADHD.

So are there any differences in risk depending on whether someone is diagnosed in childhood versus adulthood?

“We do not know,” said Beeri. “Theoretically speaking, ADHD is a chronic condition beginning in childhood and continuing to adulthood so we could assume that those who were diagnosed with ADHD in adulthood likely had it all their lives.”

She noted that, on the other hand, some characteristics differ, suggesting that childhood and adulthood ADHD could be considered separate conditions.

However, researchers noted that for this particular study, they lacked information on child onset ADHD and their exact symptomatology.

“Furthermore, our study established an association between adult ADHD and dementia,” said Sandin. “However, future studies are needed to closer examine the causal path, for example, the associations may be due to unknown confounding factors—genetic or environmental.”

How Patients Can Prioritize Future Cognitive Function

Beeri emphasized that their findings don’t prove that ADHD causes dementia, just that there appears to be a link.

“Based on our findings, we can only state that there is a relationship between ADHD and dementia,” she said. “Little evidence of reverse causation suggests that, if biologically connected, ADHD might lead to dementia rather than the other way around.”

She added that it’s important to note that when accounting for medication, the link between ADHD and dementia weakens.

This could imply that medicated individuals might not have an increased dementia risk. Alternatively, it might indicate that medicated individuals represent true ADHD patients with severe symptoms.

”Further research is necessary to explore potential common biological mechanisms between ADHD and dementia,” said Beeri. “Additionally, clinical trials are needed to investigate whether psychostimulants can reduce dementia risk in older adults with a history of ADHD.”

The study also noted that adult ADHD may be associated with an increased risk of dementia based on common health outcomes that have modifiable risk factors like depression, midlife hypertension, and smoking.

“In addition to adult ADHD, diabetes, high blood pressure, and lack of physical exercise all increase dementia risk,” said Sandin. “In the context of these many risk factors, one should try to preserve both good general health and good cognitive health.”