Now, new research is showing that adult ADHD may take a toll on the brain and is linked to a higher likelihood of developing dementia. A study published in JAMA Network Open reported that being diagnosed with ADHD as an adult is associated with a 2.77-fold increased risk of dementia.
The study only showed an association and doesn’t tell us whether ADHD is a direct cause of cognitive decline. But the results suggest that “if you do have attention-deficit disorder, you’re going to have more trouble with normal brain aging,” said Sandra Black, a cognitive neurologist at Sunnybrook Research Institute in Toronto who was not involved in the study. “It adds another risk factor.”
The research highlights the importance of seeking care — and the need for more research. Treatment with psychostimulant medications may attenuate the risk, said Stephen Levine, a professor at the University of Haifa’s School of Public Health in Israel and the lead author of the study. Lifestyle changes, such as better sleep and staying socially engaged, can also lower risk for dementia.
To investigate the link between adult ADHD and dementia, Levine and his colleagues analyzed the electronic health records of 109,218 Israeli adults 51 to 70 years old. The participants had no existing diagnosis of ADHD or dementia at the beginning of the study.
When researchers followed up with the participants over 17 years later, 730 adults (0.7 percent) had received a diagnosis of ADHD and 7,726 adults (7.1 percent) had received a diagnosis of dementia. Notably, of the 730 participants with adult ADHD, 13.2 percent (96 participants) were diagnosed with dementia. In contrast, of the 108,388 participants without adult ADHD, just 7 percent (7,630 participants) developed dementia.
Intriguingly, adults with ADHD who were taking a psychostimulant medication such as Ritalin or Adderall did not have an increased risk of developing dementia compared with those not taking medication. Only 22.3 percent of people with ADHD had taken a psychostimulant medication at any point.
One of the strengths of the research is that it takes into account 18 other potentially confounding factors. The new study “gets at the heart of this question” of whether having ADHD itself confers dementia risk, said Sara Becker, a postdoctoral research associate at the University of Calgary who was not involved in the study.
For example, adults with ADHD are more likely to smoke and to have comorbid health conditions such as hypertension and depression, which also are known risk factors for dementia. But even when controlling for these other factors, the increased risk associated with adult ADHD and dementia remained.
A handful of studies have investigated the link between adult ADHD and dementia. In a 2023 systematic review, Becker and her colleagues identified only seven previous studies investigating the link between ADHD and neurodegenerative diseases such as dementia, most of which found that adult ADHD conferred a higher dementia risk.
Parents of children with ADHD should not panic. This research studied only older adults, and it is not able to extrapolate how ADHD earlier in life would affect dementia risk, Levine said. Only about half of childhood ADHD persists to be diagnosed as ADHD in adulthood, and there is debate about whether childhood ADHD is distinct from adult ADHD.
What is clear is that more research into adult ADHD is required, researchers said. “Older adults with ADHD have relatively been understudied,” Becker said.
An estimated 3 percent of adults have ADHD, but the preponderance of research focuses on childhood ADHD.
“We don’t know much about adult ADHD, and we have to, as a society, ask ourselves, ‘Shouldn’t we know about the disease entity?’” Levine said.
Lower ‘brain reserve’ and increased need for monitoring ADHD
It is not yet known what biological mechanisms may account for the link between ADHD and dementia, but it is possible that adults who have ADHD subsequently have less “brain reserve” or capacity to maintain cognitive functioning and compensate for age-related changes.
Attentional deficit disorder may make people more subject to pathobiological changes in the brain associated with dementias, Black said.
So far, “nobody’s really looking at the biological basis of this,” Becker said. Because ADHD is linked to worse vascular health, Becker and her colleagues are currently investigating whether specific vascular changes in the brain are linked to the increased risk for dementia.
The new study also indicated that both ADHD and dementia are likely to be underdiagnosed in older adults. ADHD in particular is not something that clinicians or patients are likely to suspect. ADHD and dementia have some similarities in their cognitive symptoms, which can be easy to conflate: For instance, if someone is not paying attention to what their spouse is saying, they are also less likely to remember what was said. Identifying and diagnosing attentional issues early can allow those struggling with such issues to receive treatment for the chronic condition.
“It’s a message that policymakers, caregivers, patients and clinicians, as well as individuals, with ADHD or without, who suspect they have it should consider the reliable monitoring of ADHD in adult old age,” Levine said.
How to mitigate the risk of dementia
It is understandable to worry about developing dementia, but “it’s not that everyone who has ADHD in their adult life is going to get dementia,” Becker said. “If you take care of yourself, like anyone else in the general population, you can mitigate this risk.”
Although the study’s results provide a “positive sign” for the long-term effects of psychostimulant medications, it is too early to recommend them without further clinical testing, especially when weighing the added cardiovascular risks in older adults, Levine said.
“If there is a potential for psychostimulant medication to mitigate the risk of dementia in individuals with ADHD, then we need to provide resources for further research to confirm that possibility,” Levine said.
But there are other well-studied ways for adults, with and without ADHD, to reduce their dementia risk.
A 2020 landmark study by the Lancet Commission highlighted 12 modifiable factors for dementia that, if addressed, could mitigate the risk of dementia by up to 40 percent. Some of these factors are hearing loss, excessive alcohol intake and smoking.
“Be aware of risk factors. Take good care of your health. Take good care of your brain, everything that we tell everyone to do,” Becker said.
Do you have a question about human behavior or neuroscience? Email BrainMatters@washpost.com and we may answer it in a future column.