27 Genetic Variants Linked to ADHD
Topic: ADHD and ADD
Author: Aarhus University
Published: 2023/02/11 - Peer-Reviewed: Yes
Contents: Summary - Definition - Introduction - Main Item - Related Topics
Synopsis: An international study has identified 27 loci in the human genome with genetic variants that increase the risk of ADHD - more than twice as many as previous studies found. Together with national and international partners, the researchers have studied more than six million genetic variants in 38,691 people with ADHD and 186,843 people without ADHD. The term "genetic variants" means specific variations in the DNA code - in this case, variants observed more frequently in people with ADHD than those without the diagnosis.
Introduction
Genome-wide Analyses of ADHD Identify 27 Risk Loci, Refine the Genetic Architecture and Implicate Several Cognitive Domains - Nature Genetics.
A large international study led by Danish researchers has identified 27 loci in the human genome with genetic variants that increase the risk of ADHD. This is more than twice as many as previous studies have found.
Main Item
Why do some people get ADHD while others do not? And how early in life or the womb is the seed of ADHD sown?
Researchers from Aarhus University have come closer to answering this question in a large study, which has just been published in the journal Nature Genetics.
Together with national and international partners, the researchers have studied more than six million genetic variants in 38,691 people with ADHD and 186,843 without ADHD. This means it has been possible to identify 27 genetic risk variants for the common neurodevelopmental disorder.
Risk Genes Are Expressed in The Brain and Neurons
The study is ground-breaking, among other things, because it finds more than twice as many risk variants as previous studies have identified.
The term "genetic variants" means specific variations in the DNA code - in this case, variants observed more frequently in people with ADHD than in people without the diagnosis. Genetic variations affect, for example, the degree to which a gene is expressed and the amount of protein encoded by the gene.
By linking the genetic variants - i.e., the variations in DNA - to specific genes, the researchers have gained new knowledge about which tissues and cell types are particularly affected in individuals with ADHD. The study is based on data from the Danish iPSYCH cohort, deCODE Genetics in Iceland, and the Psychiatric Genomics Consortium.
Subsequently, the researchers combined the results with existing data on gene expression in different tissues, cell types, and brain development stages, and they discovered that genes involved in ADHD have a particularly high level of expression in a wide range of brain tissues and early in brain development - already at the embryonic stage.
"This emphasizes that ADHD should be seen as a developmental brain disorder and that this is most likely influenced by genes that have a major impact on the brain's early development," says Professor Ditte Demontis of the Department of Biomedicine at Aarhus University, who is first author of the study.
In addition, the researchers found that the genetics that increases the risk of ADHD particularly affect genes that are expressed in neurons, especially dopaminergic neurons.
"This is interesting because dopamine plays a role in relation to the reward response in the brain and because a frequently used form of ADHD medicine works by increasing the concentration of dopamine in different brain regions. Our results indicate that the imbalance in dopamine in the brains of people with ADHD is partly attributable to genetic risk factors," says Ditte Demontis.
Associated with Reduced Concentration Capacity and Short-Term Memory
ADHD is influenced by many common genetic variants, each of which increases the risk slightly, says the professor.
With the help of advanced statistical models, the researchers have estimated that around 7,300 common genetic variants increase the risk of ADHD. It is exciting that the vast majority of these variants - 84-98 percent - also have an influence on other mental disorders, e.g., autism, depression, and schizophrenia.
It has previously been shown that risk variants for ADHD can affect a person's cognitive abilities.
To investigate this further, the researchers analyzed data from an independent dataset consisting of 4,973 people who had undergone extensive neuro-cognitive tests. By using information from the new study about which variants increase the risk of ADHD, they found in the independent data set that an increased load of ADHD risk variants in the genome of an individual is associated with reduced reading and mathematical abilities, reduced attention, and reduced short-term memory.
"The results increase our knowledge of the biological mechanisms underlying ADHD, and they point to specific genes, tissues, and cell types involved in ADHD. This knowledge can be used as a starting point for further studies of the disease mechanisms and identification of new drug targets," explains Ditte Demontis.
And the study must be followed up, she emphasizes.
"We have only mapped a small fraction of the common variants that influence ADHD - just 27 of the 7,300 that potentially exist. So there is a need for larger genetic studies," she says.
International Cross-Disciplinary Collaboration is the Way Forward
Large international collaborations are crucial to identifying the genetic causes of psychiatric diseases and neurodevelopmental disorders because to do so requires studies of tens or hundreds of thousands of people with these conditions. Just as in the current ADHD study, there are often 100 or more researchers involved with different areas of expertise, such as genetics, psychiatry, psychology, epidemiology, molecular biology, statistics, bioinformatics, and computer science.
" To understand more of the genetic and biological mechanisms, it is important to have even larger studies involving more people with ADHD," says Professor Anders Børglum of the Department of Biomedicine, Aarhus University, who is the last author of the study and one of the research directors of the Danish iPSYCH project.
"But it is also important to undertake studies that focus on identifying how the genetic risk variants perturb biological processes in the brain cells (the neurons) and their way of joining up and communicating with each other in the brain. For the latter, both brain cells and early developmental stages of the brain, so-called mini-brains or brain organoids, are currently being examined," he says.
Behind the Research Results
The study is a genome-wide association study (GWAS): a study design in which the genome is screened for many millions of genetic variants among thousands of people who are affected and thousands of healthy people to identify genetic variants that are statistically overrepresented in those who are affected, compared to those who are healthy. Partners: iPSYCH, deCODE Genetics from Iceland, and the Psychiatric Genomics Consortium (ADHD working group). External funding: Lundbeck Foundation.
Your Genes Determine Whether You Get ADHD or Autism
Attribution/Source(s):
This peer reviewed publication was selected for publishing by the editors of Disabled World due to its significant relevance to the disability community. Originally authored by Aarhus University, and published on 2023/02/11, the content may have been edited for style, clarity, or brevity. For further details or clarifications, Aarhus University can be contacted at international.au.dk. NOTE: Disabled World does not provide any warranties or endorsements related to this article.
Explore Related Topics
1 - ADD vs. ADHD: Understanding the Differences - Both ADD and ADHD conditions fall under the broader category of attention deficit disorders, but they present with different symptoms and challenges.
2 - 27 Genetic Variants Linked to ADHD - An international study has identified 27 loci in the human genome with genetic variants that increase the risk of ADHD - more than twice as many as previous studies found.
3 - Are Youngest in the Class Overmedicated - The youngest children in a school grade are diagnosed with ADHD almost twice as often as the oldest in the class, suggesting age is a primary driver behind the diagnosis.
4 - Biomarkers of Child ADHD Identified - Study reveals ADHD is a neurological disorder with neuro-structural and functional manifestations in the brain, not just a purely externalized behavior syndrome.
5 - Obese Pregnant Women with Diabetes Twice as Likely to Have ADHD Child - The study found pregnant women with obesity and gestational diabetes had children with long-term mental health disorders such as ADHD.
Page Information, Citing and Disclaimer
Disabled World is a comprehensive online resource that provides information and news related to disabilities, assistive technologies, and accessibility issues. Founded in 2004 our website covers a wide range of topics, including disability rights, healthcare, education, employment, and independent living, with the goal of supporting the disability community and their families.
Cite This Page (APA): Aarhus University. (2023, February 11). 27 Genetic Variants Linked to ADHD. Disabled World. Retrieved October 5, 2024 from www.disabled-world.com/health/neurology/adhd-autism/27-variants.php
Permalink: <a href="https://www.disabled-world.com/health/neurology/adhd-autism/27-variants.php">27 Genetic Variants Linked to ADHD</a>: An international study has identified 27 loci in the human genome with genetic variants that increase the risk of ADHD - more than twice as many as previous studies found.
Disabled World provides general information only. Materials presented are never meant to substitute for qualified medical care. Any 3rd party offering or advertising does not constitute an endorsement.