What is the influence of genetic factors in ADHD? How strongly is ADHD inherited?
ADHD and Genetics
In public, ADHD/ADD or the hyperkinetic syndrome is often attributed to poor or missing education of parents or media influence or other social factors. But there are very convincing and clear scientific proof that these syndromes are inherited and thus there are strong genetic factors behind the development of ADHD.
This has been shown by numerous genetic studies, but also by twin studies. Partially identical twins were investigated. The influence of environmental factors were also considered in these studies.
Fact: With a share of 70-80 per cent of the factors influencing ADHD, the genetic factors are higher than for almost any other psychiatric or somatic illness.
So What is the "risk" for the inheritance of ADHD?
Patients with ADHD often ask whether there is an increased risk for the inheritance of ADHD on their children.
Usual information on the chances of genetic inheritance (based on a film of Russell Barkley)
- - If your own father (biological father) has ADHD: you have a risk of 30-50% of getting ADHD.
- If your mother has ADHD, you have a risk of 15-20% of getting ADHD.
- If your brother or sister has ADHD you have a risk of 25-35% of getting ADHD.
- Between twins (research done on both one-egg and two-egg twins) you have a 75 - 92% probability of getting ADHD.
Two adults who both have ADHD have between 25 and 54 percent probability of their children getting ADHD!
Can you measure by a genetic test and predict in some way if a child will have ADHD?
The answer is "No".There is no genetic test which can predict whether your children will have ADHD. Even if we do not consider whether this is ethically acceptable or even desirable, a genetic test or a prediction whether your children will inherit ADHD from you is very improbable. This is because ADHD is caused by a combination of many different genes, probably about 40 different genes to different degrees. This is called a polygenic influence and one cannot measure such a complex genetic effect. One can thus not examine a single gene or chromosome and derive or exclude, whether this will cause ADHD.