ADHD cause unlikely to be dopamine dysfunction
A new study in the journal Brain by University of Cambridge researchers suggests that the main cause of attention deficit hyperactivity disorder (ADHD) is to be found in structural differences in the brain's grey matter, not due to a dopamine dysfunction as some believed.
Dopamine is a naturally produced chemical in the brain that is important for concentration or sustained attention, working memory and motivation. It helps carry signals between brain cells by attaching to dopamine cell receptors-special entry-points in cell membranes that can only be opened by that particular molecule. Ritalin-a drug helpful for ADHD-works by raising levels of dopamine, causing more to bind to the cells and thus increase the communication between them.
Using sophisticated neuroimaging techniques, these researchers found that both the ADHD patients and the controls who were given Ritalin showed similar increases of dopamine in their brain. They also showed equivalent levels of improvement in the attention and concentration tasks. Both groups also had similar levels of dopamine receptors in an area of the brain called the striatum, and Ritalin increased dopamine in this area to the same degree. There was only one major difference: participants with ADHD as a group had significantly less grey matter in the brain, and performed much worse in the attention tests than the healthy controls.
Although these landmark results are vital towards understanding ADHD, Dr. Levinson considers it important to integrate these results with those showing significant white matter (communicating brain tracts) reductions in ADHD as well as cerebellar-vestibular neurological signs. It is also important to explain why ADHD overlaps with,or is comorbid, with a group of other disorders assumed to have diverse brain origins, eg. dyslexia or LD, anxiety and mood disorders, etc. According to Levinson, "We must consider the possibility that ADHD and all comorbid disorders stem from a common primary origin. And perhaps the differences found within the grey and white brain matter may be either secondary or important predisposing manifestations."
About Harold Levinson, M.D.
Formerly Clinical Associate Professor of Psychiatry at New York University Medical Center, Dr. Harold Levinson is currently Director of the Levinson Medical Center for Learning Disabilities in Great Neck, New York. He is a well known neuropsychiatrist, clinical researcher and author. His "highly original" research into the cerebellar-vestibular (inner-ear) origins and treatment of dyslexia and related learning, attention-deficit/hyperactivity and anxiety or phobic disorders has evolved over the past four decades. Levinson's concepts encompass the collective insights derived from the examinations, follow-up and successful treatment of over 35,000 children, adults and even seniors and have led to new methods of screening, diagnosis, treatment and prevention. His expanded theories appear capable of encompassing and/or explaining all reported symptoms as well as most other concepts and experimental data, thus resulting in a truly holistic perspective.
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