Adults with ADHD face higher risk of dementia, new study finds

Adults diagnosed with attention-deficit/hyperactivity disorder (ADHD) are nearly three times more likely to develop dementia than those without the condition, according to a large new study published in JAMA Network Open. The study followed over 100,000 individuals for more than 17 years and found a significant link between adult ADHD and future dementia, even after accounting for a wide range of health and lifestyle factors.

Dementia is a growing public health concern worldwide. In the United States alone, about 6.5 million people aged 65 or older were living with dementia in 2022. That number is expected to more than double by 2060. With no cure currently available, identifying risk factors that might help delay or prevent dementia is a top priority.

ADHD is commonly diagnosed in childhood, but more recent evidence suggests that some people develop it in adulthood or continue to have symptoms later in life. Adult ADHD often presents differently than childhood ADHD, and it remains underdiagnosed—especially in older adults.

Previous research has hinted that ADHD and dementia may be connected. Both conditions involve problems with attention and memory, and some of the same risk factors—such as depression, low physical activity, and smoking—are common in both. Family studies also suggest that people with ADHD may be more likely to have relatives with dementia, raising the possibility of shared genetic or environmental causes. However, past studies have produced mixed results, and many questions remain, including whether ADHD medications affect this risk.

This study was designed to take a closer look at whether adults with ADHD are more likely to develop dementia, and to rule out other explanations like medication use or early dementia symptoms being mistaken for ADHD.

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The researchers used a large national health database from Israel’s Meuhedet Healthcare Services, one of the country’s nonprofit health maintenance organizations. The database includes comprehensive medical records for about 14 percent of Israel’s population and is considered reliable for tracking chronic health conditions.

The study included 109,218 adults who were born between 1933 and 1952 and had no prior diagnosis of ADHD or dementia before the year 2003. The average age at the start of the study was about 58 years. Participants were followed from 2003 until they died, left the healthcare system, were diagnosed with dementia, or until the study ended in early 2020—an average of 17.2 years.

During this time, the researchers identified who developed adult ADHD and who went on to be diagnosed with dementia. ADHD diagnoses were made by trained professionals using standardized assessments. Dementia diagnoses were made by specialists like neurologists, geriatricians, or psychiatrists, using international diagnostic codes.

The researchers also collected detailed information on each participant’s age, sex, neighborhood socioeconomic status, smoking habits, and a wide range of health conditions, including depression, obesity, diabetes, heart disease, Parkinson’s disease, and traumatic brain injury. They also tracked whether participants with ADHD were prescribed psychostimulant medications, such as those commonly used to treat attention problems.

By the end of the follow-up period, 730 participants had received an adult ADHD diagnosis, and 7,726 had developed dementia. Among those with ADHD, 13.2 percent developed dementia, compared to 7 percent of those without ADHD. After adjusting for age, health conditions, and other factors, the researchers found that adults with ADHD were 2.77 times more likely to develop dementia than those without the diagnosis.

This increased risk remained statistically significant even when the researchers conducted additional analyses to test the strength of the findings. For example, they split the data by sex, age groups, smoking status, and whether participants had been prescribed ADHD medications. Across most of these subgroups, the link between adult ADHD and dementia stayed strong.

Interestingly, the researchers did not find a clear increase in dementia risk among adults with ADHD who were treated with psychostimulant medications. This could mean several things. One possibility is that medication helps protect against later cognitive decline. Another is that people who take medication may have more severe symptoms, or that those diagnosed and treated are more accurately identified. Since only about one in five adults with ADHD in the study received medication, it was difficult to draw firm conclusions about its role.

The researchers also examined whether the link between ADHD and dementia might be explained by reverse causation. In other words, could early dementia symptoms have been misdiagnosed as ADHD? To address this, they looked at when ADHD was diagnosed in relation to dementia. The results suggested some overlap between the two, but not enough to explain the entire association.

The study’s lead authors, including researchers from the University of Haifa, Rutgers University, and the Icahn School of Medicine at Mount Sinai, say the findings underscore the importance of paying attention to ADHD symptoms in older adults. While ADHD is often thought of as a childhood disorder, it may have long-term consequences for brain health that stretch into old age.

One possible explanation for the link is that adult ADHD reflects long-standing differences in brain function that make it harder for individuals to cope with the effects of aging and disease. In this view, ADHD might reduce what’s known as cognitive reserve—the brain’s ability to adapt to damage without showing symptoms.

There are also questions about whether untreated ADHD leads to other behaviors or conditions, such as smoking, depression, or lack of exercise, that may in turn increase dementia risk. While the study controlled for many of these factors, it’s still possible that other, unmeasured variables contributed to the results.

Like all observational research, this study cannot prove that ADHD causes dementia. It only shows a strong association. Because it relied on clinical diagnoses, it likely missed people with mild or undiagnosed ADHD. The same is true for dementia, which is often underdiagnosed, especially in its early stages.

The study also lacked data on certain factors that could influence brain health, such as lifelong educational achievement or genetic risk. It couldn’t assess how severe ADHD symptoms were, or how long they had been present. And although it included information on stimulant medications, it couldn’t examine other treatments like therapy or lifestyle changes.

Future research should aim to confirm these findings in other populations and explore whether treating ADHD in adulthood can reduce the risk of dementia later on. It may also be helpful to investigate whether certain ADHD symptoms—such as inattention or impulsivity—are more strongly linked to cognitive decline than others.

The study, “Adult Attention-Deficit/Hyperactivity Disorder and the Risk of Dementia,” was authored by Stephen Z. Levine, Anat Rotstein, Arad Kodesh, Sven Sandin, Brian K. Lee, Galit Weinstein, Michal Schnaider Beeri, and Abraham Reichenberg.