The effects of changes in medication use between 14 and 24 months follow-up on effectiveness (symptom ratings) and growth (height and weight measures) were analyzed, comparing 4 groups of patients, in the Multimodal Treatment Study of ADHD (MTA) reported by the MTA Cooperative Group. The patient groups were as follows: 1) treated with medication alone (Med Mgt), 2) combined medication/behavior modification (Comb), 3) behavior modification alone (Beh), and 4) community comparison (CC). Changes in medication use between 14 and 24 month follow-up formed 4 subgroups: Med/Med, Med/NoMed, NoMed/Med, and NoMed/NoMed. The Comb and Med/Mgt groups that showed the greatest improvement at the end of the 14 month treatment phase had deteriorated at 24 month follow-up whereas the Beh and CC groups showing a lesser response at 14 months had not deteriorated by 24 months follow-up. No significant differences in the 14- to 24-month growth rates were recorded among the 4 randomly assigned groups, whereas significant growth suppression had occurred in the Comb and Med/Mgt groups after 14 months of the treatment phase. Changes in medication use in the 14-24 month follow-up phase were associated with changes in ADHD and ODD symptom ratings: the subgroup stopping medication (MED/NoMed) showed the largest deterioration, the subgroups with continuous medication (Med/Med) or no medication (NoMed/NoMed) showed modest deterioration, and the subgroup starting medication (NoMed/Med) showed improvement in ADHD symptoms. The group with consistent medication use (Med/Med) showed reduced growth rate compared to the group on no medication (NoMed/NoMed) which showed accelerated growth compared to population norms. 
COMMENT. Consistent use of stimulant medication is associated with maintained effectiveness but continued mild growth suppression. A smaller growth suppression effect is observed in patients receiving interrupted treatment. The hypothesis that an initial growth suppression effect will dissipate and growth rebound will occur even when medication is continued through summer vacations, as postulated by Satterfield et al (1979), is not supported by the MTA study. Ultimate adult height (age 16 years in girls and 18 years in boys) is determined by rate of growth as well as length of growth phase. Children in the MTA follow-up phase were between 9 and 11 years of age, before the expected phase of accelerated growth. The authors propose that consistent treatment may reduce the rate but lengthen the duration of growth, so that adult height would be delayed but not reduced. Until more long-term studies are completed, recommendations for stimulant treatment of ADHD should when practical include drug holidays and lowest effective doses.