ADHD Gene May Have Benefited Early Humans - A gene variation associated with attention-deficit/hyperactivity disorder
(ADHD) first appeared 10,000 to 40,000 years ago, and may have been advantageous to early humans, according to a new report.
Up to half of ADHD individuals have this variant gene,'' lead investigator Dr. Robert K. Moyzis of the University of California, Irvine, told Reuters Health in an interview.
ADHD is characterized by impulsiveness, difficulty with academic and social
functioning, and short attention span. It is commonly treated with the
stimulant drug Ritalin
The researchers speculate that during that period of human evolution, characteristics associated with ADHD that are considered a hindrance in today's classrooms, such as novelty-seeking behavior, may have been beneficial to humans.
Early humans with the variant gene may have also been more successfulat mating and reproduction, the authors note, which would explain why the gene variation is so widespread now.
A variation of the gene DRD4, known as 7R, has been linked both to ADHD and to the `novelty-seeking'' personality trait. In their study, published in the January 8th issue of the Proceedings of the National Academy of Sciences the researchers sequenced the DRD4 genes of 600 individualsfrom around the world.
Fifty-six variations of the gene were identified. After analyzing the different variants, the investigators concluded that the 7R variant appeared recently in human evolution and may have provided some evolutionary advantage.
`We speculate that the very traits that may be advantageous for individuals possessing this variant gene may predispose behaviors that are deemed
inappropriate in the typical classroom setting,'' Moyzis told Reuters Health.
`If so, then for some ADHD individuals, alternative methods of education may be more useful than medication,'' he added. ''This study also provides a clue to why ADHD is so pervasive and may show us a way to provide more effective treatments.''
SOURCE: Proceedings of the National Academy of Sciences
2002;99:309-314. NEW YORK (Reuters Health)
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