Chemical Imbalance Is Probably Not Behind ADHD

Scientists question dopamine’s involvement

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PsychCentral reports of a study performed by Cambridge University that challenges the popular idea that dopamine is the culprit behind ADHD. Dopamine serves as a key neurotransmitter (carries signals between brain cells) that helps regulate cognitive function including the ability to pay attention.

The researchers suggest that ADHD is more likely due to structural brain differences, including reduced brain size. To determine this, the scientists gave Ritalin to some participants while others got a placebo. They were then required to test their ability to pay attention over a period of time.

“While the results show that Ritalin has a ‘therapeutic’ effect to improve performance, it does not appear to be related to fundamental underlying impairments in the dopamine system in ADHD,” said co-author Trevor Robbins, Ph.D., director of the MRC Centre for Behavioural and Clinical Neuroscience Institute.

PsychCentral reports that, “The researchers discovered that both the ADHD patients and the controls who were given Ritalin showed similar increases of dopamine in their brain, as well as similar levels of improvement in attention and concentration.”

These results are similar to previous studies which report that the ability to increase attention is attained by almost anyone taking Ritalin. This might account for its vast increase in illicit use among high-school and college students. It also implies that it is used as a shot-gun approach to ADHD therapy rather than a specific drug targeting brain function. The most important finding is that the study suggests there may not be a dysfunction in dopamine regulation in ADHD patients.

Unfortunately, Ritalin is often used to diagnose ADHD. A 20 minute evaluation by a family doctor results in a prescription with an, “If this helps, then it’s ADHD,” approach. We now know that Ritalin likely will have the same effect for most of the people taking it; it will improve their ability to pay attention. Therefore, it is not an effective method to diagnose ADHD.

“These new findings demonstrate that poor performers, including healthy volunteers, were helped by the treatment, and this improvement was related to increases in dopamine in the brain,” said Barbara Sahakian, Ph.D, study lead author.