Mrs. Jones makes an appointment to see you in your office because her son, 9-year-old Geoff, is diagnosed with ADHD. She’s considering giving him stimulant medication, along with tutoring at school, to improve his falling academic performance. But she’s hesitating because an article on the Internet said that “ritalin stunts your growth” and she wants your advice.

Most clinicians are familiar with appetite suppression weight loss in patients they treat with stimulants. What Mrs. Jones really wants to know are the long-term effects on the growth of her son — here the waters get a little murky. Will Geoff achieve his predicted adult height? Unfortunately, there aren’t too many well-designed studies providing us with decent longitudinal data. A good trial would look at a group of children with ADHD and compare their growth before and after treatment with stimulant medication, ideally over many years until maturity.

Temporary measures

A recent paper has done an analysis of studies looking at the question of growth deficits in kids treated with stimulants.¹ The authors point out that they could not do a true metanalysis because of disparity between the studies and they offer us instead a qualitative review. They conclude that deficits in growth occur with all stimulants. This effect is most marked in younger children and in the tallest and heaviest. Furthermore, the longer a child is on medication the greater the effect on height. The good news is that these effects appear to diminish with time.

The lack of a well-designed study that can answer the question of whether or not kids reach their predicted adult height and weight on meds has led some researchers to look into the problem. Kramer et al² studied 97 young adults at ages 21-23 who had been treated with stimulants for ADHD between ages 4 and 12 for an average of 36 months. Their adult height and weight did not differ significantly from those of their fathers, untreated brothers, unmedicated children with behavioural problems, or randomly selected classmates without ADHD. Although reassuring, there are several weaknesses in this study, including the fact that the authors did not actually measure the subjects in adulthood but relied on self-reporting.

Suppressed appetite is key

What is the mechanism of growth deficits in treated ADHD children? An obvious one is suppressed appetite leading to decreased caloric intake. Another suggested mechanism is the dopaminergic effect of stimulant medications; dopamine inhibits growth hormone secretion. Stimulants have also been shown to interfere with cartilage growth.³

Clearly more research is required to help us understand the effects of stimulants on growth, but in the meantime, what strategies can we adopt to mitigate these effects? First, we need to inform Mrs. Jones that these medications do indeed have an effect on growth. Weight loss is a common observation but this is usually due to appetite suppression and can be overcome with nutritional strategies: make certain the medication is given after breakfast; provide the child with a nutritious after-school snack, and so on. Secondly, another strategy supported by the literature is a drug holiday during the summer months. It has been shown in several trials that rebound growth occurs during this time.⁴ Clinical judgement is important here because taking an adolescent off medication, for example, may increase the risk of substance abuse or a serious car accident if the teenager is driving.

Finally, it’s incumbent upon the physician to carefully monitor the growth (height and weight) of the patients they are treating with these drugs, remembering first and foremost that physicians should do no harm. We must balance the proven benefits of stimulant medication in treating ADHD against the possible adverse effects on growth. The trade-off may be between academic/social success and the loss of 1-2 cm of height. Where significant effects on growth occur, it may become necessary to discontinue stimulants and consider other treament strategies.