Secondary evaluations of MTA 36-month outcomes: propensity score and growth mixture model analyses.
OBJECTIVE: To evaluate two hypotheses: that self-selection bias contributed to lack of medication advantage at the 36-month assessment of the Multimodal Treatment Study of Children With ADHD (MTA) and that overall improvement over time obscured treatment effects in subgroups with different outcome trajectories. METHOD: Propensity score analyses, using baseline characteristics and severity of attention-deficit/hyperactivity disorder symptoms at follow-up, established five subgroups (quintiles) based on tendency to take medication at the 36-month assessment. Growth mixture model (GMM) analyses were performed to identify subgroups (classes) with different patterns of outcome over time. RESULTS: All five propensity subgroups showed initial advantage of medication that disappeared by the 36-month assessment. GMM analyses identified heterogeneity of trajectories over time and three classes: class 1 (34% of the MTA sample) with initial small improvement followed by gradual improvement that produced significant medication effects; class 2 (52%) with initial large improvement maintained for 3 years and overrepresentation of cases treated with the MTA Medication Algorithm; and class 3 (14%) with initial large improvement followed by deterioration. CONCLUSIONS: We failed to confirm the self-selection hypothesis. We found suggestive evidence of residual but not current benefits of assigned medication in class 2 and small current benefits of actual treatment with medication in class 1.
Swanson, JM; Hinshaw, SP; Arnold, LE; Gibbons, RD; Marcus, S; Hur, K; Jensen, PS; Vitiello, B; Abikoff, HB; Greenhill, LL; Hechtman, L; Pelham, WE; Wells, KC; Conners, CK; March, JS; Elliott, GR; Epstein, JN; Hoagwood, K; Hoza, B; Molina, BSG; Newcorn, JH; Severe, JB; Wigal, T
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