Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 2 28 differential effects of stimulants on specific academic subjects. Secondly, Prasad and colleagues reported on the number of items correct, a measure that might be confounded by the number of items attempted (task productivity), rather than percentage correct. Therefore, improvements in items completed correctly, may merely reflect increased productivity. It is thus important to distinguish between improvements in accuracy and productivity, especially because long-term studies suggest that improvements in test scores with medication are often not accompanied by improvements in longer-term academic outcomes, such as grades and grade repetition (Arnold et al., 2015; Langberg & Becker, 2012). Ultimately, prior reviews have not resolved the key question of whether there are improvements in core academic skills or just improvements in academic productivity. Here we conducted a meta-analysis to address this issue. Our meta-analysis improved upon previous work in several aspects. First, in contrast to the previous reviews, we quantified both accuracy and productivity while distinguishing between the core academic subjects (math, reading and spelling). Secondly, we added six years of literature to the prior meta-analysis (Prasad et al., 2013), which more than doubled the number of studies included. Thirdly, these more recent studies allowed for exploration of the moderating effects of demographic and disorder related variables (age, gender, ADHD subtype and severity, and commonly reported comorbidity with oppositional defiant disorder, conduct disorder and learning disorders) and study characteristics (medication release system, dosage, titration method, time of measurement [i.e., hours after intake] and trial duration) on medication efficacy. Fourthly, we followed up on recent studies suggesting that academic improvements due to stimulant medication were partly mediated by behavioral improvements (Froehlich et al., 2014; Kortekaas- Rijlaarsdam et al., 2017b). Therefore, the current meta-analysis included symptom improvements and on-task behavior (% time on task) as potential mediators in the analyses. ME T HODS This systematic review conformed to PRISMA (Moher, Liberati, Tetzlaff, & Altman, 2009). Study Selection We included studies published in the English language in peer-reviewed journals that: (1) evaluated the effects of stimulant medication on academic functioning; (2) included mostly (at least 80% of the sample) primary school children (male and female) with a