Effects of methylphenidate on cognitive functions in children and adolescents with attention-deficit/hyperactivity disorder: evidence from a systematic review and a meta-analysis.
BACKGROUND
Attention-deficit/hyperactivity disorder (ADHD) is associated with a broad range of neuropsychological impairments. The relationship between these neuropsychological deficits and the defining symptoms of ADHD seems more complex than originally thought. Methylphenidate (MPH) is an effective treatment for ADHD symptoms, but its impact on cognition is less clearly understood.


METHODS
With a common systematic search strategy and a rigorous coding and data extraction strategy across domains, we searched electronic databases to identify published placebo controlled trials that compared MPH and placebo on executive and nonexecutive memory, reaction time, reaction time variability and response inhibition in children and adolescents (5-18 years) with a formal diagnosis of ADHD.


RESULTS
Sixty studies were included in the review, of which 36 contained sufficient data for meta-analysis. Methylphenidate was superior to placebo in all five meta-analyses: executive memory, standardized mean difference (SMD) .26, 95% confidence interval (CI): -.39 to -.13; non-executive memory, SMD .60, 95% CI: -.79 to -.41; reaction time, SMD .24, 95% CI: -.33 to -.15; reaction time variability, SMD .62, 95% CI: -.90 to -.34; response inhibition, SMD .41, 95% CI: -.55 to -.27.


CONCLUSIONS
These data support the potentially important effects of MPH on various aspects of cognition known to be associated with ADHD. Consideration should be given to adding cognitive outcomes to the assessment of treatment outcome in ADHD, considering the complexity of the relationship between ADHD symptoms and cognition.
Division of Neuroscience, Medical Research Institute, University of Dundee, Ninewells Hospital. Electronic address: d.r.coghill@dundee.ac.uk.
David R
DR
Coghill
Division of Neuroscience, Medical Research Institute, University of Dundee, Ninewells Hospital; National Health Service Tayside, Child and Adolescent Mental Health Service, Dundee, United Kingdom.
Sarah
S
Seth
Department of Child and Adolescent Psychiatry, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal.
Sara
S
Pedroso
UMEE (Unità Multidisciplinare per l'età evolutiva) ASUR , Jesi.
Tatiana
T
Usala
Division of Neuroscience, Medical Research Institute, University of Dundee, Ninewells Hospital.
John
J
Currie
Department of Pediatric Science, University of Messina, Policlinico Universitario G. Martino, Messina, Italy.
Antonella
A
Gagliano
D000367:Age Factors; D001289:Attention Deficit Disorder with Hyperactivity / Q000150:complications; D000697:Central Nervous System Stimulants / Q000627:therapeutic use*; D003072:Cognition Disorders / Q000188:drug therapy* / Q000209:etiology; D008774:Methylphenidate / Q000627:therapeutic use*; D009483:Neuropsychological Tests
D000697:Central Nervous System Stimulants; D008774:Methylphenidate
ADHD; cognition; inhibition; memory; meta-analysis; methylphenidate; neuropsychology; systematic review