Professor Orly Rubinsten and colleagues found that methylphenidate affects the arithmetic performance of children in different ways, but its effects are not only on children with ADHD. When they received methylphenidate, the active ingredient in Ritalin, children had higher correct responding on problems requiring them to follow a series of steps than when they didn’t receive the drug; in contrast, there were no differences between drug and no-drug conditions on simpler tasks. The effects occurred for children with dyscalculia, less math problems, or no math problems.
Methylphenidate has Differential Effects on Numerical Abilities in ADHD Children with and without Co-Morbid Mathematical Difficulties
Authors: Orly Rubinsten, Anne-Claude Bedard, Rosemary Tannock
Objective. To investigate effects of methylphenidate (MPH) on numerical performance in children with Attention- Deficit/Hyperactivity Disorder (ADHD) with and without concurrent math difficulties. Method. Data were analyzed from three groups of children with ADHD, who varied in arithmetic abilities. Groups were matched for IQ and reading abilities and classification was based on ICD-10 criteria, using scores on a standardized arithmetic achievement test. Thus, we identified one group with severe difficulties in arithmetic (ADHD+Developmental Dyscalculia; DD), second group with more general and less severe difficulties in arithmetic (ADHD+Mathematical Disabilities; MD), and a third group with good arithmetic abilities (ADHD). All children completed a 10-minute arithmetic task involving subtraction problems, during an acute, randomized, placebo-controlled cross-over trial with three dose levels of methylphenidate (10mg, 15mg, 20mg). Results. (1) Both ADHD+MD and ADHD+DD were impaired in using strategies that implicate working memory (i.e., borrowing). However, only the ADHD+DD were impaired in using implicit knowledge of quantities (i.e., doing simple subtractions). (2) MPH improved all children’s performance of arithmetic procedures (borrowing) that involves working memory, but had no effect on basic numerical skills that involves understanding of quantities. Conclusions. We show clear dissociation of MPH functions: it improves working memory functions but does not improve specific cognitive functions such as quantity manipulation. Moreover, MPH shows decreased efficacy for arithmetic performance in ADHD+DD, highlighting the need for additional intervention in this subgroup.
Keywords: Methylphenidate, developmental dyscalculia, ADHD
Affiliation: Neurosciences and Mental Health Research Program, Research Institute, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario, Canada.
The study appeared in The Open Psychology Journal and the entire article is available for free via the Open Journal initiative.