Objective: To conduct a post hoc investigation of the utility of a single c
omposite measure of treatment outcome for the NIMH Collaborative Multisite
Multimodal Treatment Study of Children With Attention-Deficit/Hyperactivity
Disorder (MTA) at 14 months postbaseline. Background: Examination of multi
ple measures one at a time in the main MTA intent-to-treat outcome analyses
failed to detect a statistically significant advantage of combined treatme
nt (Comb) over medication management (MedMgt). A measure that increases pow
er and precision using a single outcome score may be a useful alternative t
o multiple outcome measures. Method: Factor analysis of baseline scores yie
lded two "source factors" (parent and teacher) and one "instrument factor"
(parent-child interactions). A composite score was created from the average
of standardized parent and teacher measures. Results: The composite was in
ternally consistent (alpha = .83), reliable (test-retest over 3 months = 0.
86), and correlated 0.61 with clinician global judgments. In an intent-to-t
reat analysis, Comb was statistically significantly better than all other t
reatments, with effect sizes ranging from small (0.28) versus MedMgt, to mo
derately large (0.70) versus a community comparison group. Conclusions: A c
omposite of ADHD variables may be an important tool in future treatment tri
als with ADHD and may avoid some of the statistical limitations of multiple
measures.