To the Editor Philipsen and colleagues1 reported data from the Comparison of Methylphenidate and Psychotherapy in Adult ADHD Study, the longest-running methylphenidate trial in adults with attention-deficit/hyperactivity disorder (ADHD) to date. They concluded that: “Psychological interventions resulted in better outcomes during a 1-year period when combined with methylphenidate as compared with placebo.”1 The difference between methylphenidate and placebo was statistically significant for the outcome of observer-rated Conners Adult ADHD Rating Scale index after 52 weeks; however, it was very small, only −2.2 points (95% CI, −3.5 to −1.0) on a scale from 0 to 36 points. One study design feature could have caused such a difference.