Anne Fleur Kortekaas-Rijlaarsdam

31 MPH AND ACADEMIC PERFORMANCE: META-ANALYSIS 2 Math and reading tasks were always speeded tasks requiring participants to complete as many items in a limited amount of time. Math tasks always consisted of simple math problems (addition, subtraction, multiplication and division) generally presented in ascending order of difficulty over a fixed period of time. Reading tasks consisted of a short passage text followed by multiple choice questions. Reading paragraphs were adapted to the student’s reading level. Meta-analyses were performed for math accuracy, math productivity, reading accuracy and reading number attempted. The latter was chosen as an outcome because reading productivity could not be calculated as the total number of reading items differed per study and was not reported in combination with reading number attempted. Reading number attempted is an informative measure as the included studies used identical tasks and time limits. Spelling was measured by spelling lists assigned by teachers or taken from local school district lists. Only two out of three studies from our search reported spelling accuracy (Douglas, Barr, O’Neill, & Britton, 1986; Pelham, Bender, & Caddell, 1985), the third study only reported standardized means related to baseline scores (Bental & Tirosh, 2008). As only two studies met inclusion criteria and minimum number of studies to perform a meta- analysis is three (Borenstein, Hedges, Higgins, & Rothstein, 2009) we limited our analysis to a narrative description and qualitative synthesis. Mediators ADHD symptom improvements were included as mediators if means and standard deviations were available. Because the number of studies reporting on parent-rated symptom improvements or on-task behavior were limited (n=2 and n=8, respectively) and at least ten studies are recommended for reliable meta-regression (Borenstein et al., 2009), we only included teacher-rated symptom improvements in our mediator analysis and performed meta-regression for math accuracy (n=17) and math productivity (n=11). Teacher-rated symptom improvements were measured with standardized questionnaires, which were either derivatives from the Conners Rating Scale (Loney & Milich, 1982), the Strength and Weakness of ADHD-symptoms and Normal Behavior (SWAN) rating scale (Hay, Bennett, Levy, Sergeant, & Swanson, 2007; James Swanson et al., 1994) or the Swanson, Kotkin, Agler, M-Flynn, and Pelham (SKAMP) rating scale. SKAMP ratings show high correlations ( r = .50 - .84) with Conners ratings scales (Wigal, Gupta, Guinta, & Swanson, 1998). Supplementary material Table E2.2 gives an overview of all questionnaires used in the studies included in this meta-analysis. Reliability and validity of all questionnaires used has been established (Conners, 1997; Wigal et al., 1998). Scores were standardized (mean difference between conditions divided by SD of the placebo condition) for inclusion in the meta-regression. Mediators were investigated using meta- regression, using difference scores (MPH minus placebo).