Anne Fleur Kortekaas-Rijlaarsdam

143 SUMMARY AND DISCUSSION 7 all children (children with ADHD as well as TD children) profited equally from rewarded feedback. This runs with the grain of the increasing popularity of inclusive education. Overall, the results from this thesis suggest that stimulant medication needs to be used judiciously, specifically the most commonly prescribed stimulant MPH, in normalizing school performance in children with ADHD. Although MPH shows potential to influence certain academic skills (math and reading), effects are small in comparison to behavioral improvements with MPH and qualitative improvements are small and restricted to math. Together, these results infer that, when improvement of academic abilities is one of the main treatment goals, MPH does not have the potential to normalize school performance in children with ADHD. Treating physicians, parents and teachers should therefore make informed decisions on optimal treatment and also consider other treatments (e.g. interventions aiming at improving parent- and teacher functioning, see Daley et al., 2014). Future research should therefore also focus on the potential of nonpharmacological treatments to normalize academic performance in children with ADHD. Strengths and Limitations The current thesis has several strengths: Findings from a thorough aggregation of more than three decades of research on MPH-effects on academic performance were extended with a double-blind placebo-controlled crossover study measured MPH- effects in a realistic school setting, using reliable and validated (standardized) academic tasks. Further, we extensively studied a wide range of behavioral, cognitive and motivational factors that were likely to influence MPH-effects on academic performance. When available, we used multiple respondent formats for an outcome (e.g. self-, parent- and teacher reports) to increase validity and reliability. An important issue to address here is the value of short term randomized controlled studies, such as the ones described in this thesis, to investigate the direct effects of MPH on academic performance. This type of study is the only methodologically valid type of study to investigate medication-efficacy as it allowed trials to be double-blind and placebo-controlled. This is important as placebo-effects are generally large in this type of study and patients cannot be blinded when treatment is compared to no treatment (Krogsbøll et al., 2009). Although the results from our meta-analysis (Chapter 2) revealed no effects of study duration on MPH-effectivity, duration of these studies varied considerably between one and 21 days (per treatment condition) with most studies spanning seven days. Longer term placebo-controlled trials (with