Timothy McDonald reported this story on Monday, January 21, 2013 08:12:00

TONY EASTLEY: There are plenty of parents concerned about the negative effects of ADHD (attention deficit hyperactivity disorder) drugs on their children.



Now research published in the Medical Journal of Australia has found that teenage boys who spent three years on stimulant medication for ADHD were thinner, shorter and progressed more slowly through puberty. The effect was more pronounced among those who were on higher dosages.



The study's lead author is Dr Alison Poulton from the University of Sydney. She's been speaking with AM's Timothy McDonald.



ALISON POULTON: If a child stays on medication for three years they are about three centimetres shorter than they would be otherwise. So the obvious question is, well, if it's having this effect on growth, is it just slowing growth or is it slowing physical development?



So the next thing, one of the things that you can look at is what's the effect on puberty so that's what this study was about.



TIMOTHY MCDONALD: What did the study find?



ALISON POULTON: The boys aged 12 to 14 were leaner and the boys aged 14 to 16 were not only slimmer but also slightly less tall.



And when we asked them about their puberty the boys aged 12 to 14 were at an equivalent stage of the normal non-ADHD boys, suggesting that boys with ADHD on stimulant medication enter puberty at the same age as other boys. But the boys aged 14 to 16 were a bit behind in their pubertal stage, suggesting that they progress more slowly through puberty.



And when we looked at the growth rate, how fast they were growing in height, we found that the bigger the dose, the slower their growth rate. So that suggests that this is an effect of medication.



TIMOTHY MCDONALD: Does it also argue that perhaps doctors who are prescribing ADHD medication should be careful about what dosage they give?



ALISON POULTON: That's important anyway. But the fear is that if you've got a significant problem that you're treating, so if a child is having a lot of trouble functioning at school or with their friends and the decision is made to treat, it is important to give a dose that's high enough to give that child the maximum benefit. But of course you don't want to give more medication than they need because of course the higher the dose, the more the effect.



So it's really important to keep in mind what's the benefits for that child and balance that against the disadvantages.



But I suppose on the positive side, once you stop medication the appetite increases, they eat more and they have catch-up growth.



TIMOTHY MCDONALD: So this is a problem that ultimately resolves itself?



ALISON POULTON: Well, that's what we believe. I mean this cohort of children that we are studying, they haven't yet reached their adult height and I don't have data of my own on this. But other studies have suggested that men who are treated for ADHD in childhood end up a comparable height to their brothers and fathers.



The best evidence we have is that it doesn't have an effect on adult height but it probably takes them a bit longer to reach there.



TONY EASTLEY: Dr Alison Poulton from the University of Sydney; Timothy McDonald our reporter there.