University of Minnesota researchers assert that adolescents adopted as infants are twice as likely to have behavioral disorders compared with those who were not adopted.

Working with three large adoption agencies in Minnesota, Margaret Keyes, a research psychologist with the university's Minnesota Center for Twin and Family Research, and her colleagues interviewed nearly 700 adopted children and 540 non-adopted children, all ages 11 to 21, as well as parents, mental health professionals and teachers.

The study found that among the adopted kids, 14 percent had attention deficit hyperactivity disorder, compared with 7 percent of the non-adopted kids. Children with this disease have a hard time controlling their behavior and paying attention.

Also, 19 percent of the adopted kids met the criteria for oppositional defiant disorder compared with 10 percent of the non-adopted kids. Overall, the adopted kids had at least one mental health problem.

“Despite the popularity of adoption, there is persistent concern that adopted children may be at a heightened risk for mental health or adjustment problems,” the study authors wrote.

About 1.5 million children and teenagers under 18 in the U.S. are adopted. International adoptions are increasingly replacing domestic adoptions, with about 40,000 children transferred between more than 100 countries each year as a result of adoption.

According to Keyes, adopted children are 2.5 to 6 times more likely to show up in counselors’ office for help compared with non-adopted kids. In fact, agencies specialized in adoption provide counseling programs for adoptive families to help them cope.

Despite the findings, Keyes stressed that adoptive parents or those considering adoption should not be alarmed or discouraged by the study. She advises adoptive parents to be on the lookout for problem behaviors and to rely on the network of mental health providers they built up when applying to adopt their children in the first place.

“All adolescents struggle with finding their identity. It makes sense adopted children would struggle more than most,” she said.