Of possible interest to clinicians is that pulvinar reduction in the youths with ADHD in this study was largely driven by those who were not receiving treatment with psychostimulants at the time of the scan. The youths with ADHD who were medicated had thalamic surface morphology more closely resembling that of typically developing youths and thalamic volumes that tended to be larger than those of their unmedicated counterparts. This finding adds to other demonstrations that psychostimulant treatment in ADHD is associated with more normative brain dimensions—including white matter (1) and key regions implicated in the pathogenesis of the disorder, such as the dorsolateral prefrontal cortex (8), the anterior cingulate cortex, and the cerebellar vermis (9). However, as the authors stress, these associations should not be overinterpreted. First, in this study, among the subgroup of 17 medicated patients for whom treatment duration could be determined, greater duration of treatment was associated with smaller volumes in regions of the right pulvinar that did not show the main effect of diagnosis—a finding running somewhat counter to the finding of pulvinar enlargement associated with psychostimulant treatment at the time of the scan. More generally, causality cannot be inferred from observational studies, and a definitive demonstration of any trophic effects of psychostimulants awaits a neuroimaging study conducted within the context of a randomized trial.