Acute neuropsychological effects of methylphenidate in stimulant drug-naïve boys with ADHD II--broader executive and non-executive domains.
BACKGROUND
Accumulating evidence supports methylphenidate-induced enhancement of neuropsychological functioning in attention deficit hyperactivity disorder (ADHD). The present study was designed to investigate the acute effects of the psychostimulant drug, methylphenidate (MPH), on neuropsychological performance in stimulant naïve boys with ADHD.


METHODS
Seventy-three drug-naïve boys (age 7-15) with ADHD (combined type) completed neuropsychological tasks from the CANTAB battery under randomised, placebo controlled, double-blind conditions following an acute challenge with either placebo (n = 24), .3 (n = 25) or .6 (n = 24) mg/kg oral MPH.


RESULTS
MPH did not impair performance on any task. MPH (.6 mg/kg) lengthened response latencies on a task of Spatial Recognition, shortened response times on a Reaction Time task and restored performance on a Delayed Matching to Sample visual, non-working memory task. Contrary to predictions, MPH did not enhance performance on tasks with a prominent executive component, including Go/NoGo, Spatial Working Memory, Stockings of Cambridge and Attentional Set shifting tasks.


CONCLUSIONS
Acute administration of MPH to drug-naïve boys with ADHD did not impair neuropsychological performance. Acute MPH enhanced performance on some aspects of non-executive functioning. MPH-induced slowing of responding on a relatively complex Spatial Recognition memory task and quickened responding on a reaction time task requiring less cognitive resources suggests that MPH may act by improving self-regulatory ability. MPH may not exert its effects on neuropsychological functioning by enhancing executive processes.
Rhodes
Sinéad M
SM
Section of Psychiatry and Behavioural Sciences, Division of Pathology and Neuroscience, University of Dundee, Ninewells Medical School, Dundee, UK.
Coghill
David R
DR
Matthews
Keith
K
D000293:Adolescent; D001288:Attention / Q000187:drug effects; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis / Q000188:drug therapy* / Q000523:psychology; D000697:Central Nervous System Stimulants / Q000627:therapeutic use*; D002648:Child; D004311:Double-Blind Method; D006801:Humans; D007389:Internal-External Control; D008297:Male; D011939:Mental Recall / Q000187:drug effects; D008774:Methylphenidate / Q000627:therapeutic use*; D009483:Neuropsychological Tests; D009949:Orientation / Q000187:drug effects; D010364:Pattern Recognition, Visual / Q000187:drug effects; D011340:Problem Solving / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects
D000697:Central Nervous System Stimulants; D008774:Methylphenidate