In Reply We thank Allison and colleagues for their letter, comprising 5 key points. First, the authors suggest that the outcomes from the Monitoring Outcomes of Borderline Personality Disorder in Youth (MOBY)1 study do not represent true treatment effects based on 1 comparison study. Our interpretation is based on 4 pieces of evidence: Headspace data on routine care for young people in Australia,2 the natural history of the outcome variables, the rapid rate of change on symptom measures, and the consistency of our findings. We never sought to represent Headspace data as a clinical trial comparator. These are the best available data and are highly relevant despite limitations, such as the quality of diagnoses. These data were collected over a similar epoch (2013-2017); have a similar participant mean age (19.7 years), sex distribution (81% female), and geographical distribution (45% collected in the Australian state where MOBY was conducted); and had a similar mix of clinician disciplines. While the follow-up period for Headspace was the last occasion of service, for some participants this took place after 30 treatment sessions.