Adults with ADHD have increased risk of obesity, epilepsy and a number of other diseases

Obesity, epilepsy, alcohol-related liver disease, fatty liver, sleep disorders and COPD.

These are some of the many diseases that Swedish researchers have now found to have the strongest link to ADHD.

People with ADHD also have a slightly increased risk of cardiovascular disease, Parkinson's disease and dementia.

Biological explanation found

ADHD is a disorder characterized by inattention, impulsivity and hyperactivity.

For a long time it was thought that ADHD occurred due to poor upbringing or poor care. Many people did not regard the diagnosis as a 'real' disease, in contrast to cancer and heart attacks.

A research breakthrough took place in 2018, when an international research group discovered several genetic variants related to ADHD.

Professor Jan Haavik at the University of Bergen’s KG Jebsen Centre for Neuropsychiatric Disorders has been researching ADHD for many years. His research team contributed to the breakthrough.

Study examined four million people

The 2018 study is the basis for several new studies on biological mechanisms related to ADHD.

Researchers at the Karolinska Institute in Sweden have now examined over four million people using Swedish patient registers.

They looked at the risk of 35 different physical illnesses in people with ADHD.

The researchers compared them with the risk of disease in people without this diagnosis.

They also compared the results with the risks for siblings of people with and without an ADHD diagnosis.

Genes play biggest role

The researchers wanted to look at whether the link between ADHD and the various physical illnesses was due to genes or the environment.

They concluded that genes play the biggest role in this link because they found that the full siblings of those with ADHD likewise have a significantly increased risk for most of the physical illnesses.

Large and thorough study

Haavik at the University of Bergen thinks the study is interesting, “not least because it’s so big. This makes it very robust methodically.”

The results don’t surprise him.

In 2016, he and colleagues in Bergen conducted a study that summarized the research on the topic.

They found that ADHD was significantly associated with a number of diseases, such as obesity, sleep disorders and asthma. They also found some links between ADHD and celiac disease and migraines.

The researchers in Bergen pointed out that few large and thorough studies are available in this area of research.

The researchers at Karolinska took the Bergen research as the starting point for their large registry study.

Studied autoimmune diseases

Haavik believes that the results from this and other studies could indicate that there aren’t that many unique ADHD genes.

“Instead, there’s reason to believe that a lot of genes are involved and that they can affect several biological processes,” he says.

His research group now has a study ready for publication, in which they go into more detail on immunological mechanisms. They were able to access the Swedish registers and look more closely at the connection between ADHD and all autoimmune diseases.

This study will soon be published in a scientific journal.

May have an impact on treatment

“When researchers find common biological vulnerability factors for several diseases, it could have an impact on the treatment of ADHD,” Haavik says.

“This can provide inspiration to look for a new therapy. Maybe we’ll find medications that can be used across diagnoses, at least in some groups of patients.”

Haavik says recognizing that psychiatric disorders like ADHD are often accompanied by somatic illness is important for anyone treating such conditions.

“This has a bearing on diagnostics, the choice and dosage of drugs, as well as the possible side effects and interactions of the drugs,” he says.

No revolution

Researchers haven’t known what mechanisms in the brain they should target in the treatment of ADHD, because they haven’t understood the biology of the condition.

Treatment of these patients has thus been somewhat random.

Haavik believes it may be time to go a step further and take biology as the starting point.

“Within somatic medicine, we’re seeing that drugs based on genetic mechanisms are yielding greater success. We may come to the same realization in psychiatry,” he says.

“But,” he points out, “it’s a long and arduous process.”

“This probably won’t be a revolution. But we’re inspired by what we’ve seen in cancer treatment. That field has taken small steps in the direction of finding groups of patients who need a more tailored treatment. This process could also work for psychiatry,” Haavik says.

Translated by: Ingrid P. Nuse

References:

Ebba Du Rietz et.al.: Mapping phenotypic and aetiological associations between ADHD and physical conditions in adulthood in Sweden: a genetically informed register study, The Lancet Psychiatry, June 2021.

Den norske ADHD-forskeren. Interview with Jan Haavik on adhdnorge.no (in Norwegian).

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Read the Norwegian version of this article at forskning.no