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Genetics | Environmental Risk Factors
Excerpt
The genetics of ADHD have been explored via three types of
studies—family/adoption studies, twin studies,
and, more recently, molecular genetic studies. Family studies have
consistently shown that if a child has ADHD, 10%–35% of
first-degree relatives are likely to have the disorder as well (Biederman et al. 1992). If a parent has ADHD, the risk to the child
of developing ADHD is as high as 57% (Biederman et al. 1995a). Sprich et al. (2000) examined the
rates of ADHD in the relatives of both adopted (i.e., nonbiological)
and nonadopted children with ADHD. The rate of ADHD in biological
relatives of children with ADHD was 18% compared to only
6% in the adopted relatives, suggesting a strong genetic
effect.