New Research Finds Possible Link Between ADHD and Dementia

A large, multigenerational study at Karolinska Institutet in Sweden has found a possible link between attention-deficit/hyperactivity disorder (ADHD) and the risk of dementia and Alzheimer's disease. The research, published in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, shows that parents and grandparents of individuals with ADHD were at higher risk of dementia than those with children and grandchildren without ADHD.

While the findings suggest that there are common genetic and/or environmental contributions to the association between ADHD and dementia, the researchers say further studies are needed to understand the underlying mechanisms.

ADHD and Cognitive Decline

The study examined more than two million people born in Sweden between 1980 and 2001, of whom around 3.2% were diagnosed with ADHD. The researchers used national registries to link these individuals to more than five million biological relatives, including parents, grandparents, and uncles and aunts.

When they looked into whether these relatives developed dementia, they discovered that parents of individuals with ADHD had a 34% higher risk of dementia than parents of individuals without ADHD. The risk of Alzheimer's disease, the most common type of dementia, was 55% higher in parents of individuals with ADHD.

The researchers note that the absolute risk of dementia was low for the parent cohort—only 0.17% of the parents were diagnosed with dementia during the follow-up period.

The association was lower for second-degree relatives of individuals with ADHD, i.e. grandparents, uncles, and aunts. For instance, grandparents of people with ADHD had 10% increased risk of dementia compared to grandparents of people without ADHD.

While the study is unable to determine a cause-and-effect relationship, the researchers offer several potential explanations. They speculate that undiscovered genetic variants that contribute to both traits, or family-wide environmental risk factors, such as socioeconomic status, may have an impact on the association. Another possible explanation is that ADHD increases the risk of physical health conditions, which in turn leads to increased risk of dementia.

Psychiatrist and author Gayani DeSilva, MD, is skeptical about the research. "The causes of dementia are not yet fully understood, and worrying about it based on sketchy data is not helpful," she says. "Whatever we can do to keep our brains healthy is always a good idea."

“The number of new ADHD diagnoses has increased dramatically in the last decades amid increasing awareness and knowledge about the disorder,” says Leela R. Magavi, MD, psychiatrist and Regional Medical Director for Community Psychiatry and MindPath Care Centers. “However, since the diagnosis is still relatively new, there has only been a limited number of small studies on the development of dementia in people with ADHD, often with conflicting results.”

Dr. Magavi evaluates many children, adolescents, and adults who have ADHD, but do not have a family history of dementia or related disorders. “We need much more research to determine whether ADHD is linked to dementia,” she says. She encourages anybody who is concerned about their risk of dementia to prioritize their diet and exercise habits. “We have found that various conditions such as diabetes may be linked to dementia,” she explains.  

The Future of ADHD Research

Experts welcome further research on the link between dementia and ADHD, but other areas of study are equally important. For instance, Dr. DeSilva believes the effect of trauma on the development of ADHD needs more attention. "Clearly, trauma affects brain development—even halting it in some areas of the brain," she says. Because ADHD is a neurodevelopmental disorder, trauma may be a significant reason why some children develop ADHD, or do not "grow out of it." 

"Many symptoms of ADHD are the same as when a child is anxious or depressed (or undergoing continued trauma such as domestic violence, physical abuse, sexual abuse, neglect, and emotional abuse)," Dr. DeSilva adds. "Understanding this connection between brain development, mood, trauma, anxiety, and attention will help us develop treatments and preventive interventions to promote the health and wellbeing of our children."