Commentary: Important design features to consider in observational research on the long-term outcomes of ADHD - reflections on Sibley et al. (2017) and Swanson et al. (2017).

In this issue of the Journal, Sibley et al. (2017) presented some important insights into how different assessment approaches influence the apparent persistence of ADHD into adulthood, while Swanson et al. (2017) presented interesting results regarding the long-term benefits (adult symptom reduction) and costs (adult height suppression) associated with the treatment of ADHD with stimulant medication. This commentary highlights that (a) future studies that attempt to explore the occurrence and predictors of persisting and remitting developmental trajectories of ADHD, as well as late-onset ADHD, need to be based on thorough assessment of ADHD in adulthood using a combination of self-ratings and other informants (parents), and that (b) observational studies of the long-term benefits and risk associated with ADHD medications will play an important role in future research and clinical guidelines.