Genetic mutation may be key to ADHD (Attention Deficit Hyperactivity Disorder)

While it seems popular these days to blame ADHD on food additives, parenting and "toxins" the evidence against these causes has mounted year after year. Little if any evidence for them can be found in respected scientific journals or research. Most research has pointed to ADHD (Attention Deficit Hyperactivity Disorder) being a genetic disorder, something inherited. New research further supports this, pointing to a single-letter change in the DNA code which "may spell ADHD."

ADHD -- attention deficit hyperactivity disorder (sometimes called ADD) can be found in 5% of school-aged children to learn. Kids with ADHD may be impulsive, can't sit still, they can't focus their attention and have trouble learning and remembering. (Different combinations of these symptoms leads to "inattentive type," "hyperactive type," and "combined type." Korean researchers report that children with ADHD tend to have a particular DNA misspelling -- a single-nucleotide polymorphism or SNP -- that affects an important brain function gene called GIT1. This has long been suspected, and this research backs up the theory.

Mice genetically engineered to carry this SNP "misspelling" are hyperactive and have poor learning and memory skills. But when given stimulant ADHD drugs, these mice exhibit normal behaviour. "Our study reveals a previously unidentified role of GIT1 in ADHD and establishes a new mouse model for ADHD," conclude Hyejung Won of the Korea Advanced Institute of Science and Technology and colleagues in the journal Nature Medicine.

More recently Won and his colleagues compared the genomes of 192 Korean children with ADHD to 196 age-matched children without ADHD. It was very rare for any child to inherit copies of gene mutation from both parents. Having just one copy of the mutation meant a 2.66-fold higher risk of ADHD.

Mice needed two copies of the mutant SNP to get ADHD, not just the single copy linked to ADHD in children. But these mice had nearly all the symptoms of human ADHD -- and just like children, their symptoms improved when they got stimulant ADHD drugs.

Just like some children with ADHD, mice with the ADHD genetic mutation tended to get over their ADHD when they grew up. At a mouse age of 7 months, equivalent to human age of 20 to 30 years, ADHD symptoms spontaneously went away. (Well, we think, the "hyperactivity went away, but we don't know if these mice had difficulty with concentration, planning, procrastination and so on found in adult human!) It seems that brain cells maintain a careful balance between being in a state of excitation and one of inhibition. By affecting the function of the GIT1 gene, the ADHD-linked mutation makes brain cells more excitable. This is just the function we see addressed by ADHD medications.

What did we learn? Well, that there isn't any "bad parenting" or "bad teaching" to blame for the cause of ADHD. But there is something, several things, we can do. These interventions range from medication to cognitive behaviour therapy to environmental changes to make dealing with ADHD symptoms easier. For more information on this topic I suggest checking out Dr. Russell Barkley's books, Controlling Your ADHD and Controlling Your Adult ADHD. both provide excellent sources of information to understand the cause of ADHD and interventions that are science based. Avoid interventions that promise too much, avoid those that promise a lot too easy. Stick with interventions supported by real science.

This blog is not meant to provide therapy, interventions or diagnostic services. As always, I suggest avoiding looking for answers on-line, and especially avoiding on-line diagnostic "tests" or simple check lists of ADHD symptoms. ADHD needs to be diagnosed by a professional, and as always, that diagnosis includes ruling out other possible causes for your symptoms.

For more information, assessment and treatment please feel free to contact me at:

Dr. Jim Roche