The findings were replicated in a study of 825 Icelandic patients with ADHD and more than 35,000 Icelandic control group members.
In background materials to the study, the British researchers said they hoped their findings would help overcome the stigma associated with ADHD -- which some people associate with parenting problems or poor diet -- by suggesting that it has a genetic basis.
Finally, a third study - this time a small case-control study of about 250 children -- found that children with ADHD are more likely to suffer from depression or attempt suicide as teens.
In fact, 16 to 37 percent of those with ADHD suffer from major depressive disorder or a relatively mild form of depression known as dysthymia, noted Andrea Chronis-Tuscano of the University of Maryland and colleagues.
"These findings suggest that it is possible to identify children with ADHD at very young ages who are at very high risk for later depression and suicidal behavior," the authors wrote in the same issue of The Lancet. "Considered in light of what is already known about the antisocial outcomes of childhood ADHD and their risk for unintentional injury, it would not be premature to test early prevention programs designed to reduce both serious behavioral and affective [consequences] of ADHD in early childhood."
For more information on ADHD, visit the U.S. National Institute of Mental Health.
SOURCES: Jan Haavik, M.D., Ph.D., department of biomedicine, University of Bergen, Norway; Stephan Zuchner, M.D., associate professor, director, Center for Human Molecular Genomics, University of Miami Miller School of Medicine; Oct. 2010, Archives of General Psychiatry
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