High Dopamine Levels Alone Do Not Cause ADHD
> 12/1/2006 10:02:54 AM

In a near reversal of prevailing opinion and years of clinical practice, researchers at the Brookhaven National Labratory determined that high levels of dopamine receptors in the brain are not solely responsible for attention deficit problems and that, in fact, some patients diagnosed with related disorders displayed lower levels of activity in the same receptors. Most importantly, the extensive study's adult subjects had more pronounced problems with attention than those in the control group regardless of recorded dopamine levels. These findings suggest that earlier efforts to focus on those specific brain chemistry defects were incomplete and that immediate extensions of the new research are in order.

The number of American children and young adults diagnosed with and medicated for ADHD is rapidly rising, but its causes and definitions are still frustratingly imprecise. Though drugs like Ritalin have been prescribed for children since the early 60's, The National Institute of Mental Health only named ADHD as a legitimate psychological condition in 1998, after related clinical visits increased nearly threefold in the previous seven years. By all measures, genetics appear to play a key role in determining which children will ultimately display symptoms of the disorder. Children with other inborn neurological conditions are much more likely to be diagnosed with ADHD, and those with siblings or parents who have attention problems show a considerably greater instance of ADHD. Common opinion has long held that difficulties with pregnancy or early exposure to controlled substances and environmental toxins contribute to the likelihood of ADHD diagnoses, but extensive research has not confirmed these theories.

Dopamine transporters are proteins that attach to and absorb excess quantities of the chemical, and an overabundance of these can theoretically serve to lower the amount of the chemical distributed throughout the brain, resulting in decreased attention and motivation. The measured levels of dopamine in the subjects of previous research varied widely, and these studies often failed to control for existing medications, drug abuse, or neurological disorders, so Brookhaven researchers made sure to include only subjects who were not affected by these variables. While they regularly recorded lower levels of the transporters in ADHD subjects, inattention scores for affected subjects were still five times higher when their dopamine levels matched those of the control group. So the protein shortages common in adults with ADHD are more likely to be influenced by the condition than to cause it. This finding strongly contradicts previously held beliefs about the cause and effect relationship between dopamine and ADHD.

More than three million children in the United States alone currently receive treatment for ADHD. While some unquestionably benefit from medications like Ritalin or Adderall, well-funded and opposing camps have developed to address  public concerns about the potential for overpresciption and recreational use of these drugs. This study, using brain imaging techniques funded by the Office of Biological and Environmental Research within the U.S. Department of Energy’s Office of Science and by the Intramural Research Program of the National Institutes of Health, indicates that current treatment methods are inaccurate and possibly counterproductive. Luckily, more than one organization has a seeded interest in continuing research which could lead to more effective medicines and related therapies in the near future.

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