Study raises questions about diagnosis, medical treatme...(other ADHD populations worldwide. .....),Health

• Two genes, labeled DBH and DRD2, involved in the regulation of dopamine a neurotransmitter involved in attention, motivation and emotion have also been associated with ADHD in the population of northern Finland. Although the researchers involved say they likely account for very little of the genetic variation underlying ADHD, the findings further support the involvement of the dopamine pathway in the etiology of the disorder.

"This set of articles brings to light the necessity of engaging in new ways of thinking about ADHD," said Smalley, who is also a member of the Center for Neurobehavioral Genetics at UCLA. "Certainly it is a valid disorder in terms of its diagnosis; there are relatively similar prevalences around the world. But the predisposition to ADHD is a normal distribution in attention and activity level, much like diabetes and glucose tolerance, or dyslexia and reading disability.

"The continuous nature of liability to ADHD requires that we examine more carefully what environmental pressures may be leading to impairment, instead of broadening our diagnostic classifications even further," she said.

The study started in 1986, when researchers from Imperial College, London, and Finland's University of Oulu began studying 9,432 children in northern Finland. They tracked the children from the early fetal period to adolescence (age 16 to 18). UCLA researchers then joined in the effort to examine the adolescents for ADHD behaviors, using a standard screening survey and diagnostic criteria. Among the 6,622 respondents to the survey, a subset of 457 likely cases and controls were evaluated for ADHD and other psychiatric disorders. The estimated prevalence of ADHD among these adolescents was 8.5 percent, with a male-female ratio of 5.7 to 1.

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