title: Mediators of methylphenidate effects on math performance in children with attention-deficit hyperactivity disorder.
abstract: OBJECTIVE
  Stimulant medications, such as methylphenidate (MPH), improve the academic performance of children with attention-deficit hyperactivity disorder (ADHD). However, the mechanism by which MPH exerts an effect on academic performance is unclear. We examined MPH effects on math performance and investigated possible mediation of MPH effects by changes in time on-task, inhibitory control, selective attention, and reaction time variability.
  
  
  METHODS
  Children with ADHD aged 7 to 11 years (N = 93) completed a timed math worksheet (with problems tailored to each individual's level of proficiency) and 2 neuropsychological tasks (Go/No-Go and Child Attention Network Test) at baseline, then participated in a 4-week, randomized, controlled, titration trial of MPH. Children were then randomly assigned to their optimal MPH dose or placebo for 1 week (administered double-blind) and repeated the math and neuropsychological tasks (posttest). Baseline and posttest videorecordings of children performing the math task were coded to assess time on-task.
  
  
  RESULTS
  Children taking MPH completed 23 more math problems at posttest compared to baseline, whereas the placebo group completed 24 fewer problems on posttest versus baseline, but the effects on math accuracy (percent correct) did not differ. Path analyses revealed that only change in time on-task was a significant mediator of MPH's improvements in math productivity.
  
  
  CONCLUSIONS
  MPH-derived math productivity improvements may be explained in part by increased time spent on-task, rather than improvements in neurocognitive parameters, such as inhibitory control, selective attention, or reaction time variability.
authors: *Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH; †Department of Psychology, University of Cincinnati, Cincinnati, OH; ‡Department of Psychology, Virginia Commonwealth University, Richmond, VA.
authors: Tanya E
authors: TE
authors: Froehlich
authors: Tanya N
authors: TN
authors: Antonini
authors: William B
authors: WB
authors: Brinkman
authors: Joshua M
authors: JM
authors: Langberg
authors: John O
authors: JO
authors: Simon
authors: Ryan
authors: R
authors: Adams
authors: Bridget
authors: B
authors: Fredstrom
authors: Megan E
authors: ME
authors: Narad
authors: Kathleen M
authors: KM
authors: Kingery
authors: Mekibib
authors: M
authors: Altaye
authors: Heather
authors: H
authors: Matheson
authors: Leanne
authors: L
authors: Tamm
authors: Jeffery N
authors: JN
authors: Epstein
mesh_terms: D001289:Attention Deficit Disorder with Hyperactivity / Q000188:drug therapy* / Q000503:physiopathology; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D002648:Child; D004311:Double-Blind Method; D004521:Educational Measurement; D006801:Humans; D007266:Inhibition, Psychological; D008297:Male; D008433:Mathematics / Q000193:education*; D008774:Methylphenidate / Q000008:administration & dosage / Q000494:pharmacology*; D009483:Neuropsychological Tests; D010919:Placebos; D011930:Reaction Time / Q000187:drug effects; D013647:Task Performance and Analysis; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D000697:Central Nervous System Stimulants; D010919:Placebos; D008774:Methylphenidate