New research from UNSW sheds light on why some people have adverse reactions to certain doses of ADHD medication, while others have good results.
The work, which has just been published in the January edition of The Australian and New Zealand Journal of Psychiatry, could eventually help to determine what type of treatment a patient should receive.
The research, which was carried out on adults, shows there are two forms of a gene (the COMT gene), which has a bearing on how the medication works in the central nervous system.
The COMT gene affects dopamine metabolism in the brain's prefrontal cortex, which is concerned with attention and memory. One version of the gene results in lower dopamine levels than the other, potentially allowing more accurate predication of medication response.
"It has been very hard to predict who will respond to treatment," said the author of the paper, Professor Florence Levy, from the School of Psychiatry at the University of New South Wales (UNSW), the Prince of Wales Hospital and Sydney Children's Hospital.
"While there have been some children that respond to very small doses of stimulant treatment, others require higher doses," said Professor Levy, who helped start the Stimulant Committee of the NSW Health Department, which monitors stimulant use in NSW.
"Those that need only small doses, but are given a larger dosage, may experience detrimental effects," said Professor Levy, who is one of the world's leading researchers in ADHD. "They may have obsessional-type symptoms, be very highly focused and unable to change their attention from one thing to another."
Stimulant medication has also been linked to a decrease in appetite and small effects on growth velocity in some children.
"There is now a new branch of psychiatry and genetics growing, called pharmaco-genomics, which is the genetics of predicting which medications will suit individuals - and that's what this is," said Professor Levy.
While the research may be useful, Professor Levy is quick to point out that there will never be a simple diagnostic test.
"Pharmaco-genomics may help, but it is more complicated than that," she said. "There are environmental effects and there may be a number of genes which influence behaviour."
Contact details: Susi Hamilton, UNSW media unit, 9385 1583 or 0422 934 024.