Assessing medication effects in the MTA study using neuropsychological outcomes.
BACKGROUND
While studies have increasingly investigated deficits in reaction time (RT) and RT variability in children with attention deficit/hyperactivity disorder (ADHD), few studies have examined the effects of stimulant medication on these important neuropsychological outcome measures.


METHODS
316 children who participated in the Multimodal Treatment Study of Children with ADHD (MTA) completed the Conners' Continuous Performance Test (CPT) at the 24-month assessment point. Outcome measures included standard CPT outcomes (e.g., errors of commission, mean hit reaction time (RT)) and RT indicators derived from an Ex-Gaussian distributional model (i.e., mu, sigma, and tau).


RESULTS
Analyses revealed significant effects of medication across all neuropsychological outcome measures. Results on the Ex-Gaussian outcome measures revealed that stimulant medication slows RT and reduces RT variability.


CONCLUSIONS
This demonstrates the importance of including analytic strategies that can accurately model the actual distributional pattern, including the positive skew. Further, the results of the study relate to several theoretical models of ADHD.
Epstein
Jeffery N
JN
Department of Psychiatry & Behavioral Sciences, Duke University Medical Center, Durham, NC 27710, USA. epste002@mc.duke.edu
Conners
C Keith
CK
Hervey
Aaron S
AS
Tonev
Simon T
ST
Arnold
L Eugene
LE
Abikoff
Howard B
HB
Elliott
Glen
G
Greenhill
Laurence L
LL
Hechtman
Lily
L
Hoagwood
Kimberly
K
Hinshaw
Stephen P
SP
Hoza
Betsy
B
Jensen
Peter S
PS
March
John S
JS
Newcorn
Jeffrey H
JH
Pelham
William E
WE
Severe
Joanne B
JB
Swanson
James M
JM
Wells
Karen
K
Vitiello
Benedetto
B
Wigal
Timothy
T