Anne Fleur Kortekaas-Rijlaarsdam

71 MPH EFFECTS ON MATH PERFORMANCE: INFLUENCE OF BEHAVIOR 3 not alter the effects of methylphenidate on math productivity or accuracy, we also performed the analyses with age as a moderator. Age did not moderate the effects of methylphenidate on any of the math outcomes (all p -values > .05). D I SCUSS I ON Academic underperformance is a major problem in ADHD (Daley & Birchwood, 2010; DuPaul, 2007; Polderman et al., 2010). With this placebo-controlled crossover study we investigated the effects of long-acting methylphenidate on academic accuracy and productivity in a realistic school setting, using reliable and validated academic tasks. Besides immediate effects of medication on academic performance, the influence of learning ability, ADHD symptom severity and symptom improvement on the effectivity of medication in improving school performance were studied. Efficacy of the methylphenidate intervention compared to placebo was confirmed by robust parent- and teacher-rated behavioral improvements with medium to large effect sizes, in line with previous studies (MTA-group, 1999b; Van der Oord et al., 2008). For academic accuracy and productivity, effects of methylphenidate were small to medium- sized and were limited to those academic subjects for which children with ADHD underperformed in comparison to typically developing children: speeded arithmetic (SAT) and mathematical word problems. For mathematical productivity on the SAT, methylphenidate treatment resulted in a two percent increase in productivity but performance did not normalize to the level of typically developing children, in line with previous studies reporting increased math productivity on comparable tasks (Froehlich et al., 2014; Prasad et al., 2013). Furthermore, with methylphenidate, a nine percent increase in mathematical word problem accuracy was observed, and performance of children with ADHD was comparable to performance of TD children. Improvements in mathematical accuracy are less commonly shown in previous studies, but not unseen (Douglas et al., 1986; Froehlich et al., 2014; Pelham Jr. et al., 1987; Tannock et al., 1989) particularly with higher dosages (Baweja et al., 2015; Prasad et al., 2013). In our study, dosage did not influence the effects of medication on any of our academic measures (data available on request). We found no effects of methylphenidate on reading or spelling. Previous studies on the effects of methylphenidate on reading and spelling are scarce with one study reporting positive effects and two studies reporting non-significant effects on reading accuracy, (Carlson et al., 1992; Elia et al., 1993; Pelham Jr. et al., 1987) and no studies reporting improvements in spelling productivity or accuracy with methylphenidate (Bental &