Anne Fleur Kortekaas-Rijlaarsdam

83 MPH EFFECTS ON MATH PERFORMANCE: INFLUENCE OF COGNITION, MOTIVATION AND PERCEIVED COMPETENCE 4 has an eight hour duration of action with a 30% component of immediate release and a 70% component of extended-release 4-5 hours after dosing (Banaschewski et al., 2006). Although we accepted applications of stimulant naïve children, children were only included after successful titration by their treating physician and after a period of stable treatment (at least 3 weeks; mean duration of treatment was 30.7 months, SD = 19.1). Titration was performed in a classical manner (increasing dose gradually until maximal symptom improvement is reached with tolerable side effects), in conformity with standard clinical practice (e.g. see NICE guidelines: “Attention deficit hyperactivity disorder: diagnosis and management,” 2016). Before enrollment in the study, medication washout was achieved using a period of at least 48 hours prior to the start of the first treatment week and between the two treatment weeks. Children were tested on the last day of each treatment week at their own primary school. Medication was prescribed by the treating physician. Doses were identical to those clinically titrated and currently prescribed. When a child was treated with immediate release MPH the long-acting equivalents was calculated taking into account differences in plasma concentrations and duration of action between the different brands of long-acting MPH, as described in Banaschewski et al. (2006). Daily doses varied between 10 and 40 mg, with 27% of the children receiving 10 mg, 44% receiving 20 mg, 24% receiving 30 mg and 5% receiving 40 mg. Both active MPH and placebo capsules were inserted in other capsules to ensure visual equality. Our academic pharmacist, who was not in contact with any participants, was responsible for randomization using predefined randomization blocks to determine medication or placebo sequence. Researchers, children, parents and teachers were blinded to the intervention. Due to the low drop-out risk randomization occurred without replacement. Materials Table 4.2 provides an overview of all cognitive and motivational variables. Cognition Verbal working memory was measured with Digit Span backwards of the WISC-III, which has good reliability and validity (Wechsler, 2005). Participants repeated sequences, with increasing span, in reversed order. The task was terminated when a child made two errors on trials of the same sequence length, or when participants reached the maximum span of seven. The dependent variable was the total number of correct responses multiplied by the highest sublevel passed (Kessels, Zandvoort van, Postma, Kapelle, & Haan de, 2010). In the visuospatial working memory task participant reproduced (Nutley et al., 2009), in backward order, sequences of yellow circles with increasing difficulty (one circle