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Study Shows Dopamine Dysfunction Isn’t the Main Cause of ADHD

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A new study that was recently published in the journal Brain shows that healthy subjects who received methylphenidate (the substance marketed as Ritalin) experienced the same increase in dopamine levels as the patients exhibiting symptoms of ADHD. According to the results of the study, both groups of subjects experienced the same improvements on their ability to concentrate and levels of attention.

The current study is led by a research team from the University of Cambridge, in collaboration with the MRC Center for Behavioral and Clinical Neuroscience Institute (BCNI). It is a double-blind study that puts all precedent suggestions about the link between ADHD and dopamine to question. Until now, one of the main causes of ADHD has been though to be an abnormality in the transmission of dopamine in the brain. However, the current study suggests that the actual cause could be found in the structural differences that are found within the grey matter of the brain. The research team believes that their results could lead to a significant improvement towards understanding and treating ADHD.

Dopamine is a crucial neurotransmitter that is involved in concentration, working memory, and attention. The way it takes part in these processes is by combining itself with specialized receptors found on the nervous cells of the brain. Methylphenidate increases the levels of dopamine in the brain, thus increasing the flow of information between the nervous cells.

Through the use of a PET (positron emission tomography) scan technique combined with fMRI (functional magnetic resonance imaging), researchers measured the effect of methylphenidate on the dopamine receptors. Both groups were given either a dose of methylphenidate, or placebo. Afterwards, the subjects were asked to perform several tasks that tested their ability to concentrate and their ability to keep their attention over a given period of time.

The group of subjects suffering from ADHD showed a significant impairment in their attention performance. Moreover, researchers discovered that methylphenidate also increased the attention performance of some of the subjects in the control group. However, the effects of methylphenidate on the levels of dopamine in the brain’s striatum, were almost the same for both groups.

According to the leader of the study, professor Barbara Sahakian, the results of the study show that the levels of concentration of anyone can be improved through the use of methylphenidate, whether or not the individuals suffer from ADHD. The novel information demonstrates that concentration can be improved by raising the levels of dopamine in the brain, specifically in the caudate nucleus of the striatum area.

The co-author of the study, professor Trevor Robbins, who is also the director of the BCNI, reports that these findings put a question mark on the precedent results of studies that suggested that the dopamine abnormalities are the main cause of ADHD. Furthermore, Robbins added that even if methylphenidate has a beneficial effect on attention performance, it is not linked to the impaired dopamine system that is found in ADHD patients.