Fred A Baughman Jr., MD comments on (10/23/02): Scientists Zero in on Gene for ADHD
Tue Oct 22, 2002 By Amy Norton NEW YORK (Reuters Health) - Researchers have identified a small spot in the human genetic makeup they believe holds a gene that plays a key role in the risk of attention-deficit/hyperactivity disorder (ADHD). [Fred A. Baughman Jr., MD:
The same genetic region has been implicated in the developmental disorder autism--suggesting, the investigators say, that the two conditions may share some genetic roots. [Fred A. Baughman Jr., MD:
The US and UK research team reports the findings in the October issue of the American Journal of Human Genetics [Fred A. Baughman Jr., MD:
. The study implicates a specific region of chromosome 16 in contributing to ADHD susceptibility--a region that past research has tied to autism risk. The finding, based on 203 families in which at least two siblings had ADHD, suggests that an as yet-unidentified gene within this chromosome region is a major ADHD risk factor. "We've narrowed the search for one of the many genes believed to be involved in ADHD," the study's lead author, Dr. Susan L. Smalley of the University of California, Los Angeles , told Reuters Health. She and her colleagues estimate that variations in a gene in this chromosome 16 region could account for about 30% of the genetic risk behind ADHD [Fred A. Baughman Jr., MD:
Experts believe that, overall, genetics account for 70% to 80% of the underlying cause of the disorder, Smalley noted. She and her colleagues focused on a specific region of chromosome 16 after a preliminary "genome scan" suggested its involvement in ADHD--and after earlier research implicated it in autism. Autism is a developmental disorder estimated to affect 1 in 500 children. To varying degrees, it impairs a child's ability to communicate, form relationships and respond normally to his or her environment. Some children with autism also show self-injurious or aggressive behavior. ADHD is far more common, and children with the disorder have greater-than-normal difficulty focusing their attention and controlling their behavior. Although autism and ADHD are "quite distinct," Smalley and her colleagues note, certain general characteristics, such as inattention and hyperactivity, mark both disorders. [Fred A. Baughman Jr., MD:
It is possible, according to Smalley, that variations in a gene in the implicated chromosome 16 region contribute to "common deficits" found in both ADHD and autism. [Fred A. Baughman Jr., MD:
However, she added, it is also possible that the two disorders involve separate genes that just happen to dwell near each other. Smalley's team is now trying to zero in on the chromosome 16 gene linked to ADHD, while continuing to comb other chromosomes for such "risk genes." According to Smalley, researchers hope that identifying the genes involved in ADHD will allow doctors to more accurately diagnose the disorder--a diagnosis that today, she noted, "is based solely on behavior." Genetic diagnosis of ADHD could also reveal that the disorder has different fundamental forms, all of which might respond differently to treatment. And, Smalley said, genetic testing could allow doctors to "pick up kids at risk before symptoms," when they could potentially be helped by preventive, non-drug therapies. SOURCE: American Journal of Human Genetics 2002;71. [Fred A. Baughman Jr., MD:
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