Growth on Stimulant Medication
© 2005 Prime Health Consultants, Inc.
Stimulant medication for the treatment of attention deficit hyperactivity disorder (ADHD) has long been suspected to have an adverse effect on linear growth. The first studies concerning this were published in the 1970s and since that time, there have been numerous other studies, which rather than clarifying this relationship, seem to have added to the controversy. Poulton reviewed 29 cohort studies published through September 2004 of children treated with methylphenidate or dexamphetamine. Twenty-two of the studies involved children, 6 involved adolescents or adults close to their adult height, and 1 study included both children and adults. Of the 29 studies, 9 gave results consistent with reduction in height growth while on stimulants and 12 had negative findings. There was a slight difference in the median medication dose (31.4 mg vs 23.9 mg) in those studies which showed significant growth attenuation. Various methods were used to describe height, but the most frequently used method was height deficit, meaning that the child was a certain amount shorter than he would have been had he continued to grow at a previous rate. Some studies used height z-scores.
The most sensitive studies were the longitudinal studies analyzing periodic observations taken before and after the initial period of treatment. Half of these studies (8 of 16) showed an attenuation of growth on the stimulants by at least 1 method, most reliably a change in height z-scores. The most scientifically rigorous study was one in which children with ADHD were randomly assigned to different treatment groups. This study showed a height deficit of 0.9 cm/yr in the first 14 months and 1.04 cm/yr from 14–24 months in children who received pharmacological treatment. Eight of the longitudinal studies used normative data as the controls, three of which showed an attenuation of height.
The studies of late adolescent and adult heights were mostly cross-sectional, and none showed any significant difference between those treated and the controls. The author stated that many of the studies were of poor quality. However, those of better quality demonstrated a significant association between treatment and attenuated height growth. The conclusion was that despite the large number of studies, most of those failed to detect any adverse affect on growth due to stimulant medication. Many did not stand up to any rigorous analysis. They further stated that it is reasonable to anticipate a reduction in height velocity when children are placed on stimulant medication, but that further studies should be performed in order to better understand the significance of this reduction.
First Editor’s Comment: This paper is a welcome analysis of a large number of studies involving stimulant medications and the measurement of height in children with ADHD. Pediatric endocrinologists are often faced with the question of whether or not stimulant medication will adversely affect growth, and it is very difficult to reference opinions with well-conducted longitudinal trials. Thus, one is left with the conclusion that the results are uncertain. Poulton has shown that at least in those studies that were more rigorously performed, there did seem to be a significant height deficit in these children. However, he also points out that children often do not remain on stimulant medications for the duration of their linear growth. Thus, an overall effect on final height is difficult to discern. This review will hopefully encourage investigators to perform the kinds of studies needed to answer this question conclusively. Such studies need to be randomized, control trials with varying doses of stimulant medications. With so many children currently receiving these medications, such a trial seems feasible.
William L. Clarke, MD
Second Editor’s Comment: The efficacy of ADHD treatment and the growth of patients was also studied by the MTA Cooperative Group at the National Institutes of Mental Health1 and reviewed in GGH.2 It was clearly documented that there were behavioral benefits in treating ADHD patients, but there was decreased growth (–1.9 cm in height suppression in 24 months). As well, there were weight changes (– 2.5 kg in the first 14 months and –1.22 kg in the following 20 months of treatment). These changes were more prominent in patients who adhered to the medication regimen. However, there were many who stopped taking the medication and thus, the effects were less marked. Suboptimal nutrition may play a role in the reduced growth and weight gain due to the effects of these medications. Thus, when these medications cannot be interrupted, physicians should attempt to overcome the decreased dietary intake and correct any nutrient deficits.
Fima Lifshitz, MD
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