A large study from Karolinska Institutet in Sweden found that ADHD and dementia can be linked across generations. The study, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s AssociationResearch shows that people with ADHD are more likely to die from dementia than their grandparents and children.
“The results suggest that ADHD and dementia share common genetic and/or environmentally-related causes. We need to do more research to understand the underlying mechanisms,” Le Zhang, a PhD student at Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics, said.
ADHD (attention-deficit/hyperactivity disorder) is a neurodevelopmental disorder characterized by inattention, impulsiveness and hyperactivity. It affects around 3 percent of adults in the world.
With increasing awareness and knowledge about ADHD, the number has increased dramatically. The diagnosis of ADHD is still relatively new. There have been very few studies that looked at the development of dementia in ADHD patients, and many of these results were conflicting.
Researchers wanted to find out if dementia was more common in older people than in those with ADHD. The study examined more than 2 million people who were born in Sweden between 1980-2001. Around 3.2 percent of them were diagnosed with ADHD. The researchers used national registries to link these people to more than five million biological relatives, including grandparents, parents, uncles, aunts, and uncles. They also investigated whether or not these relatives had developed dementia.
Researchers found that ADHD parents had a 34% higher chance of developing dementia than those without ADHD. The risk of Alzheimer’s disease (the most common type) was 55 percent higher among ADHD parents. ADHD patients were more likely to have parents who had early-onset dementia than those who had late-onset.
Researchers note that the absolute risk for dementia in the parent cohort was low; only 0.17 per cent of the parents were diagnosed as having dementia during the follow up period.
The association with ADHD was lower in second-degree relatives (i.e. The association was lower for second-degree relatives of individuals with ADHD, i.e. grandparents, uncles and aunts. For example, the dementia risk for grandparents of people with ADHD was 10 percent higher than that of grandparents of those without ADHD.
Although the study cannot prove cause-and-effect, the researchers suggest several possible explanations that could be explored in future research.
“One could think that there are undiscovered variants that contribute both traits, or familywide environmental risk factors such as socioeconomic standing that may have an influence on the association,” Zheng Chang (researcher at Karolinska Institutet’s Department of Medical Epidemiology and Biostatistics) is the study’s last writer. “Another possibility is that ADHD increases risk of developing physical conditions, which can lead to increased dementia risk.”
Materials provided by Karolinska Institutet. Note: Content may be edited to improve style and length.