Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 7 132 SUMMARY AND K E Y F I ND I NGS O F T H I S T H E S I S The main aimof this thesis was to investigate the effects of MPH on academic performance and learning. To this end, we formulated three study-aims which were answered in different parts of this thesis: Firstly, we quantified the effects of MPH on academic performance assessed in terms of both productivity and accuracy while distinguishing between the core academic subjects (math, reading and spelling). The results of the meta- analysis of 34 studies from 1980 to 2017 were described in Chapter 2. Further, the evidence from our randomized double-blind placebo-controlled crossover trial further contributed to this aim and was described in Chapter 3. Secondly, we aimed to unravel the mechanism behind MPH-effects on academic performance, thereby distinguishing between measures of academic effort (productivity) and qualitative improvements in academic performance (accuracy). For this purpose, we studied the influence of an elaborate set of carefully selected moderators and mediators on relation between MPH treatment and academic performance in children with ADHD. Moderator- and mediator analyses of pooled effects were described in the meta-analysis in Chapter 2. Moderator and mediator effects in our own crossover RCT were described in Chapters 3 and 4. The third aim was to quantify the effects of MPH on feedback learning (Chapter 5) and the interaction between MPH and reward on math performance in children with ADHD (Chapter 6). The following paragraphs give a short summary of the collected evidence relating to these three aims. This is followed by a critical discussion of the results. Table 7.1 provides an overview of the thesis aims and corresponding key findings. F I RS T A I M MPH Effects on Productivity and Accuracy in Math, Reading and Spelling Chapter 2 described a systematic review and meta-analysis summarizing results from over three decades of research on the effects of MPH on academic performance in primary school children with ADHD. PubMed, EMBASE, ERIC and PsycINFO were searched for articles reporting MPH effects on academic productivity and accuracy. Thirty-four studies met entry criteria, representing a combined total of 1777 children with ADHD. Another 425 children with ADHD from seven studies were included in a qualitative synthesis. There were small to medium sized positive effects of MPH on math accuracy (3.0% increase), math productivity (7.8% increase) and reading speed (SMD .47). Results from our qualitative synthesis corroborated these findings. The number of studies reporting on MPH effects on spelling accuracy was insufficient for meta-analysis and the qualitative synthesis of studies reporting on this topic was inconclusive as it was based on too few studies.