Efficacy of Adderall and methylphenidate in attention deficit hyperactivity disorder: A reanalysis using drug-placebo and drug-drug response curve methodology

Because methylphenidate (MPH) is currently the most widely prescribed medication for attention deficit hyperactivity disorder (ADHD), several studies have used this as the touchstone for evaluating the efficacy of a newer stimulant, Adderall. In a parallel-groups study of MPH (n = 20), Adderall (n = 20), and placebo (n = 18), Pliszka et al. (2000) reported that both medications were superior to placebo in improving parent, teacher, and clinician ratings of ADHD and associated behaviors. Compared with MPH, Adderall led to significantly more improvements in teacher and clinician ratings. The present study extends these results by addressing the issue of clinical significance using drug-placebo and drug-drug response curve analyses of the same data. The goal of this method is to answer the following questions about drug-placebo or drug-drug differences: Is the effect clinically meaningful? What does the effect tell us about individual responses? Is the effect due to symptom improvement, the prevention of worsening, or both? Our results show that the efficacy of Adderall to improve functioning is seen throughout the full range of improvement scores. In contrast, MPH showed a substantial effect for "mildly" and "much improved" but not for "very much improved." Our analyses also show that both Adderall and MPH prevent worsening of symptoms. They further suggest that, compared with the Conners Teacher Rating Scale, the Clinical Global Impressions scale may be more sensitive to improvements at the "well end" of the spectrum of functioning.