Researchers link 27 genetic variants to ADHD

"Why do some people get ADHD, while others do not? And how early in life or in 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 people without ADHD. By 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, inter alia 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 which are observed more frequently in people with ADHD than in people without the diagnosis. Variants in DNA affect, for example, the degree to which a gene is expressed and subsequently the amount of protein that is 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 -- in fact already at the embryonic stage.

"This emphasizes that ADHD should be seen as a brain developmental 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.

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.

In fact, with the help of advanced statistical models, the researchers have estimated that there are around 7,300 common genetic variants that increase the risk of ADHD. It is particularly interesting 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.

"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.

"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."

*I think the genetics and biochemistry side of mental health is so interesting! This type of research is so important because it helps us to understand the areas that these diseases come from and affect and can help us find new drugs that are more disease-specific. It's amazing how much of an impact genetics has and how each person may be slightly different. Genetics can allow for a very individualized approach to medicine and healthcare. I also wanted to share this because genetics has more to do with mental health than we realize and this can help alleviate the pressure that many people feel when facing mental health and that it's "their fault." Mental health is just the same as physical health - it is out of your control. Of course, it's important to take preventative measures and make sure you are healthy like you would with your physical health. But, we can't control our genetics and where we come from. So please be kind to yourself and know that you are amazing! What are some other factors you think impacts ADHD? If you struggle with AHDH, what are some self-care tips you use that help you feel better?*

#ADHD #Research #Genetics

Please find the full article at Science Daily.

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