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Although understanding of attention-deficit hyperactivity disorder (ADHD) has increased in recent years – leading to improved recognition and diagnosis – there is still much we do not know about this neurological difference, especially the biological mechanisms underlying its occurrence and differences in perceptions. Humanity. . One of these aspects is the role of genes, as we do not know which ones are responsible for this inheritance.
However, a new study has come to change science’s perception of this inheritance: Until now, given the complexity of ADHD, it was thought to be explained by a series of mutations in genes, but innovative research suggests that half of inherited cases come from genetic variations. Unique, that is, in only one gene, in addition to environmental or genetic factors.
Genetics and attention deficit hyperactivity disorder
The thing about polygenics, even though many scientists consider this hypothesis “obvious,” is that it cannot explain the full genetic inheritance of ADHD. Studies analyzing how genes associated with the disorder are transmitted note that only about 30% of them are inherited. Meanwhile, physical and behavioral symptoms, when observed in familial lines, have a heritability of about 80%. The bill doesn’t add up.
To investigate further, a team led by psychologist Anne Arnett of Harvard University studied the entire genomes of 77 American children with ADHD and their families. Although it is a small sample and the focus is on infants, the proposed theory explains the differences in single and multiple inheritance.
The key is unconventional methylation. DNA methylation is the body’s control over changing gene expression levels in different cells, which occurs due to external (i.e. epigenetic) influences. Thus, environmental factors such as stress, physical activity, the diet of an ancestor (like a grandmother, for example) or pollution can change methylation states in several different genes. This causes a domino effect on the body that can lead to, among other things, ADHD.
This may explain how external factors contribute to differences in brain development and the expression of symptoms of neurological aberration – similar levels of genetic variation have already been identified in autism spectrum disorder (ASD), for example. There has already been suspicion that both of these neurological differences are related, as up to 70% of individuals who show one also show the other, or at least appear in the same family.
Although some features of these disorders are opposites, they have many in common, leading some scientists to suggest that they are different parts of the same continuum. If the epigenetic theory is correct, this would explain how so many different symptoms could occur.
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