Children With ADHD Differ Genetically From People Who Are Diagnosed as Adults

Summary: Children diagnosed with ADHD have a higher genetic overlap with autism spectrum disorder while adults diagnosed with ADHD have a higher genetic overlap with depression.

Source: Aarhus University

Five percent of all school children in Denmark show symptoms of ADHD. For adults, it is around three percent. ADHD is a neurodevelopmental disorder with onset in childhood. Two-thirds of children who are diagnosed with ADHD continue to have ADHD as adults. In other cases, ADHD is not diagnosed until adulthood.

Researchers from the national psychiatry project iPSYCH have studied the genetic differences between people diagnosed during childhood and people diagnosed as adults.

“We’ve found that the genetic architecture differs depending on how old you are when you get an ADHD diagnosis,” says Associate Professor Ditte Demontis who is behind the study.

Less hyperactivity in adults

Approximately 74 percent of the risk of being diagnosed with ADHD is caused by genetics. The genetics that cause ADHD are ‘polygenic’, which means that ADHD is caused by several genetic variants in the genome, each of which contributes slightly to the risk of developing the disease. Genetic architecture is the overall term for all variants in the genome that contribute to ADHD.

In the new study, researchers analysed the genetic architecture of people diagnosed with ADHD as children and people diagnosed with ADHD as adults.

By comparing these results with the results of other large-scale genetic studies of autism and depression, the researchers discovered that the genetic architecture in children diagnosed with ADHD overlaps with autism significantly more than the genetic architecture of people diagnosed as adults. 

This shows the outline of a head
Approximately 74 percent of the risk of being diagnosed with ADHD is caused by genetics. Image is in the public domain

For individuals diagnosed with ADHD as adults, on the other hand, the genetic architecture overlaps with the genetics of depression to a much higher degree than those who are diagnosed as children. This means that people diagnosed with ADHD as adults have an increased risk of depression due in part to genetic risk factors.

The researchers also found that the genetic architecture of people diagnosed with ADHD as adults had a lower load of genetic variants involved in hyperactivity and inattention issues than people who are diagnosed with ADHD during childhood.

“In other words, people who are diagnosed with ADHD as adults are generally less genetically predisposed to be hyperactive and inattentive. This result may help to explain why the time of diagnosis occurred later in life for this particular group of people with ADHD,” explains Ditte Demontis.

Overall, these results suggest that there are differences in the underlying genetic architecture of ADHD depending on when you are diagnosed. The results of the study provide new information on which illnesses you have an increased genetic risk of developing depending on when in life you receive your ADHD diagnosis.

About this genetics and ADHD research news

Author: Helle Horskjær Hansen
Source: Aarhus University
Contact: Helle Horskjær Hansen – Aarhus University
Image: The image is in the public domain

Original Research: Closed access.
Differences in the genetic architecture of common and rare variants in childhood, persistent and late-diagnosed attention-deficit hyperactivity disorder” by Ditte Demontis et al. Nature Genetics


Differences in the genetic architecture of common and rare variants in childhood, persistent and late-diagnosed attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with onset in childhood (childhood ADHD); two-thirds of affected individuals continue to have ADHD in adulthood (persistent ADHD), and sometimes ADHD is diagnosed in adulthood (late-diagnosed ADHD).

We evaluated genetic differences among childhood (n = 14,878), persistent (n = 1,473) and late-diagnosed (n = 6,961) ADHD cases alongside 38,303 controls, and rare variant differences in 7,650 ADHD cases and 8,649 controls.

We identified four genome-wide significant loci for childhood ADHD and one for late-diagnosed ADHD. We found increased polygenic scores for ADHD in persistent ADHD compared with the other two groups.

Childhood ADHD had higher genetic overlap with hyperactivity and autism compared with late-diagnosed ADHD and the highest burden of rare protein-truncating variants in evolutionarily constrained genes.

Late-diagnosed ADHD had a larger genetic overlap with depression than childhood ADHD and no increased burden in rare protein-truncating variants.

Overall, these results suggest a genetic influence on age at first ADHD diagnosis, persistence of ADHD and the different comorbidity patterns among the groups.

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  1. I wasn’t diagnosed with ADHD as a child or adult, and I was quietly paying attention to EVERYTHING… yet able to get by and not exactly involved in any screening process then (or now)…I’m always perplexed by it being descibed as “inattentive” when in fact it can be paying attention to everything…I really think you don’t “get” Neurodiversity, when you slap “inattentive” labels on people, its far more complex and harnessed properly its a force of nature. Our institutions are way behind what is infact needed to care for all learners,Educators need to get our more and frequently mix professionally with multiple other groups ie embrace multidisciplinery concepts, like the many of us have for ages.Collaboration is critical to meet our childrens needs.

  2. Well, I’m not a scientist but, from personal experience, I wasn’t diagnosed with ADHD until adulthood because I come from a long line of mental-illness deniers. My family didn’t talk about or deal with mental health when I was growing up and continue to not talk about it. Admitting that you’re different is taboo to my family. Although, I believe there’s plenty of mental health issues in my family that need to be addressed. So, I had to address my ADD (I don’t have hyperactivity as an adult) once I was an adult. I also suffered from depression since I was a child (which went undiagnosed) so I agree with the correlation from the study but I disagree with the time of diagnosis. I still would’ve been diagnosed with ADHD and depression IF I was actually diagnosed as a child.

  3. What is the role of gender here? We know that women with ADHD are more likely to be diagnosed later because they are less likely to present as hyperactive and more likely to present as inattentive, which tends to delay identification. There is also a disparity in the presentation of autism in males and females, and in the likelihood of diagnosis in childhood. This study is quite reductive in its thinking, and doesn’t even acknowledge these issues and potential influences in their discussion, let alone in the analysis of their data.

  4. Theres a lot of room for error in these studies. Do researchers even know what Autism looks like genetically in adults? My guess is no seeing as how it’s nearly impossible to get a diagnosis/treatment/or any attention at all as an adult with Autism.

  5. Couldn’t it just be that without a childhood diagnosis you spend your whole life trying to fit in, feeling like you’re different or broken and having to mask your true self, while with a childhood diagnosis you’re free to accept the difference and people knowing about it alleviates stress. Seems to me like we’re looking at things backwards. Spending your life stressing out about feeling different can certainly wear down the body. An early diagnosis allows one to accept their differences and not view oneself as wrong or broken. Adults not being as hyperactive is because they perfected the art of hiding that part of themselves, thus higher depression risk. It all makes perfect sense. Unless you wanna argue that DNA is absolutely constant and unchanging. Then please refer to the roots of mathematics and tell me that those are 100% sound and stable.

  6. I think it also needs to be taken into account the society the individual was raised in. The public opinions on ADHD and how acceptable it is there. This will be a large factor in the age of diagnosis.

    1. I suffered from ADHD In mid childhood ,mid 1950s before it was known to science and was diagnosed in later life when had chronic depression as well ,glad to see you are getting the knowledge out there ..

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