Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 3 66 hoc analysis testing whether medication-effectivity differed between high and low ability groups (using median-split). Procedure The current study has been carried out in accordance with the Declaration of Helsinki and was approved by the local ethics committee. Parents and children above the age of 11 provided written informed consent prior to enrollment in the study. For children with ADHD, after the screening procedure confirming the ADHD diagnosis and establishing sufficient intelligence (IQ>70), testing took place on the last day of each treatment week and started 60 to 90 minutes after medication intake. Testing was done individually in a quiet room within the primary school of the child. Total testing time was 120 minutes (including breaks). Academic measures were collected by the researchers using fully standardized instructions. All procedures and scoring were double-checked. All researchers were blinded to medication condition. Testing occurred during plasma peak levels of methylphenidate (Banaschewski et al., 2006). On testing days, teachers and parents were asked complete online behavioral questionnaires covering behavior on the previous seven days. After a short explanation of the procedure, testing started with the SAT, followed by mathematical word problems, OMR and PI-dictation. The TD group was assessed only once. Testing procedures were identical in the ADHD and TD group, with the exception that the academic performance tasks of TD group were preceded by a short version of the WISC-III to estimate TD children’s IQ as TD children were first seen on the day of the assessment. Participants with ADHD received a small gift. R E SU LT S Effects of Methylphenidate on Behavior and Academic Accuracy and Productivity In the TD group data for mathematical word problems were missing for three subjects. In the ADHD group, data for mathematical word problems were missing for two subjects and for one subject data for the OMR and PI-dictation were missing. Data were normally distributed for all variables except for accuracy scores for the SAT. To account for this, two outliers (in both methylphenidate and placebo condition) were rescaled to the nearest observation in the distribution plus one unit. Results from the independent samples t-tests comparing participants from different sequence groups (methylphenidate first versus placebo first) showed no indications of carryover effects (all p >.05). Table 2 displays the results for the behavioral and academic performance measures of the ADHD group during methylphenidate and placebo and for the TD