In fact, ADHD is a “complex multigene genetic disorder”, which is definitely not as simple as the “color blindness” we learn in secondary school textbooks. In other words, the onset of ADHD is not determined by a single gene, but is associated with multiple genetic abnormalities, and the role of genetics is also governed by environmental factors. Therefore, it is the combination of genetic and environmental factors that leads to ADHD, and this is the complexity of the pathogenesis of ADHD. One study found that the prevalence of ADHD was 50% in siblings of the same parents, compared to 14% in siblings of different parents. Studies of twins have found that if one is identical (nuclear genetic identity), the prevalence of the disease in the other is as high as 100%, whereas the prevalence in heterozygous twins is much lower. This shows that genes have a clear influence on the development of ADHD. The role of genes was further confirmed by a study of foster care: only 2 out of 22 cousins of the child were affected, compared to 9 out of 19 siblings, when the child’s siblings were placed in foster care with others in similar environments. These suggest that there is a clear familial pattern of attention deficit hyperactivity disorder in children. The prevailing view is that the heritability of ADHD is 0.7-0.8, which means that genetics plays a 70-80% role in the development of ADHD, while environmental factors play only a 20% role. Of course, this is a generalization for the entire ADHD population and may vary for each individual child with ADHD. Genetics and environment are actually endogenous and exogenous. Genetics, or more specifically genes, are biological information that each individual carries in a fixed way, inherited from their parents as an “endogenous” cause. When an individual has an ADHD-causing gene, the protein encoded by the gene may be abnormal, and this abnormal function may lead to the manifestation of ADHD symptoms. So, does the presence of an ADHD gene necessarily mean that an individual will develop the disease? Not necessarily, and this is where the importance of environmental factors comes into play. Environmental factors are “exogenous” and cover a wide range of factors, including family upbringing, parent-child relationship, teachers’ education, and even the atmosphere. Good environmental factors can suppress the effects of the ADHD gene, while bad environmental factors can promote the effects of the ADHD gene. So when your child has ADHD, don’t worry about not getting better because it has genetic factors, but know that the environmental factors of your child’s life and learning also play a very important role.