A growing concern

In children with Attention Deficit Hyper Activity Disorder (ADHD), the balance between effort and reward is less favourable than for their unaffected classmates. This means that ordinary rewards, such as gold stars and good marks, aren’t enough to keep them on track. Tasks have to be easy, short, or sufficiently rewarding to get them engaged.

By Aviva Lowy

Originally published in Radius.

Sally Poulton

Sally Poulton

“Stimulant medications have been very effective in treating ADHD, which is why so many children are on them. Methylphenidate, best known under the proprietary name of Ritalin, and dexamphetamine, are the most commonly prescribed psychotropic drugs in childhood and adolescence,” says Sally Poulton, Senior Lecturer at Sydney Medical School at Nepean. She’s been treating children with ADHD for the past 16 years.

Stimulant medications affect behaviour by improving the ability to focus on tasks and to complete tasks, and by increasing motivation. But they also suppress appetite, which in turn affects growth.

“We are always concerned about weight loss in the growing child. Energy is important for growing more bone, more blood, more muscle. Height is also affected, with about one centimetre of growth being lost each year for the first three years of medication, so that after three years, these children are about one inch shorter than you’d otherwise expect them to be.”

However, the body’s drive to eat and grow in adolescence is overwhelming. The generally held belief is that, even if there is a temporary reduction in their growth rate, these children ultimately catch up and reach the height they would have achieved if they had not taken medication. With the enormous variability in puberty, though, it is hard to detect any lasting effect.

“While we don’t really want weight loss in children, if we keep drug dose so low that it doesn’t affect weight, there will be no therapeutic effect either. The two are very closely aligned.”

Poulton sees this relationship with cognition and appetite as having potential use in other settings,
particularly in achieving weight loss in obese adults. And indeed, dexamphetamine was excessively used - and abused – by dieters in the 50s and 60s, before falling into disrepute. In that incarnation, the drug was used as an appetite suppressant.

“That approach is OK, but as you lose weight, the body adapts and you have to turn the ‘thermostat’ to a lower level by continually increasing the dose. Another approach to weight loss says that you need to address lifestyle. You have to be active, you have to be motivated to keep to a diet and you need impulse control to avoid eating inappropriately.”

Stimulant medication could be used in the treatment of obesity to increase motivation in establishing a healthy lifestyle. Any suppression of appetite then becomes an added bonus, not the main focus of the drug regime. The dose could be adjusted according to behavioural outcomes rather than continually being raised to increase the weight loss.

Ironically, stimulant medications have been so successful in the treatment of children with ADHD that there has been a public backlash, with claims in the media that these drugs are being over-prescribed.

While there is surprisingly good agreement between one doctor and another in assessing a child as having ADHD, it’s extremely difficult to determine the prevalence of the condition in the community. There is some consensus that as many as 5-11% of children have ADHD. With less than 2% on medication for it, perhaps it is actually undertreated,” says Poulton.