Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 7 144 treatment periods of at least 2 months) may be more predictive of future academic performance as they allow for the inclusion of measures that are more predictive of academic achievement (e.g. grades). In addition, whether such longer term trials also allow for larger changes in actual performance (also on standardized achievement test) is questionable: On the one hand, improvements in for instance attention, feelings of competence and effort may add together over time and result in better academic performance. On the other hand, as argued above, there is no evidence that the effects of MPH on behavior and cognition are larger in longer term trials. One way or another, such longer term placebo-controlled trials are scarce because of ethical constraints and have low medication adherence and high dropout rates. Therefore, it is likely that relatively short term trials will be standard practice in this line of research, making it difficult to translate these findings to academic achievement and occupational outcomes. Thus, when drawing conclusions about the (absence) of effects of MPH on academic performance we need to carefully balance evidence from methodologically strong RCTs on direct effects with more ecologically valid studies of long term academic outcomes. When doing this, we can conclude that aggregations of effects of MPH on longer-term outcomes of academic performance (including grades, grade retention, type of education, continuation to college) also question the clinical significance of MPH-effects given their relatively small size (Langberg & Becker, 2012; Loe & Feldman, 2007). A related issue here is the use of standardized achievement tests to measure the effects of MPH on academic performance. This type of task is by far the most commonly used in this field as it allows for direct assessment of the effects of MPH, the utilization of norm-groups when required and the use of different (parallel) versions of a task to minimize learning effects in case of repeated assessment. However, standardized tests show much lower correlations with longer term educational measures (school dropout and college performance) than for instance grade point averages (Allensworth & Easton, 2007; Zwick & Green, 2007). This is an important issue as it has been shown that the effects of ADHD symptoms are most apparent on standardized tests, compared to other outcome measures such as grades, grade repetition or type of schooling (Frazier et al., 2007). This suggests that MPH-efficacy may also differ between educational outcome measures, in line with the long term findings of Arnold et al. (2015). Future research on the effects of MPH on academic performance should distinguish between quantifying the impact of MPH on core academic productivity/accuracy (which is only possible using standardized achievement tasks) and using more ecologically valid educational outcome measures.