Objective: Using an adoption study design, the authors addressed the issue of genetics in attention-deficit hyperactivity disorder (ADHD).
Method: This study examined the rates of ADHD and associated disorders in the first-degree adoptive relatives of 25 adopted probands with ADHD and compared them with those of the first-degree biological relatives of 101 nonadopted probands with ADHD and 50 nonadopted, non-ADHD control probands.
Results: Six percent of the adoptive parents of adopted ADHD probands had ADHD compared with 18% of the biological parents of nonadopted ADHD probands and 3% of the biological parents of the control probands.
Conclusion: Results of this study lend support to the hypothesis that ADHD has a genetic component.