Objective: Intent-to-treat analyses of the Multimodal Treatment Study of ADHD (MTA) revealed group differences on attention-deficit/hyperactivity disorder symptoms ratings, with better outcome in groups of participants who were assigned the medication algorithm-medication alone (MedMgt) and combined (Comb)--than in those who were not-behavior modification (Beh) alone and community comparison (CC). However, the effect size was reduced by 50% from the end of treatment to the first follow-up. The convergence of outcomes suggests differential changes by treatment group beween 14 and 24 months, which this report explores, both for benefits of treatment and for side effects on growth.
Methods: We documented reported medication use at 14- and 24-month assessments and formed 4 naturalistic subgroups (Med/Med, Med/NoMed, NoMed/Med, and NoMed/NoMed). Then we performed exploratory mediator analyses to evaluate effects of changes in medication use on 14- to 24-month change scores of effectiveness (symptom ratings) and growth (height and weight measures).
Results: The randomly assigned groups with the greatest improvement at the end of the treatment phase (Comb and MedMgt) deteriorated during the follow-up phase, but the other 2 groups (Beh and CC) did not. There were no significant differences in the 14- to 24-month growth rates among the randomly assigned groups, in contrast to significant growth suppression in the Comb and MedMgt at the end of the treatment phase. Changes in medication use mediated the 14- to 24-month change in attention-deficit/hyperactivity disorder symptom ratings: the subgroup that reported stopping medication (Med/NoMed) showed the largest deterioration, the subgroup that consistently reported (Med/Med) or never reported (NoMed/NoMed) medication use showed modest deterioration, and the subgroup that reported starting medication (NoMed/Med) showed improvement. Changes in medication use also mediated growth effects: the subgroup that consistently reported medication use (Med/Med) showed reduced height gain compared with the subgroup that never reported medication use (NoMed/NoMed), which actually grew faster than predicted by population norms.
Conclusion: In the MTA follow-up, exploratory naturalistic analyses suggest that consistent use of stimulant medication was associated with maintenance of effectiveness but continued mild growth suppression.