Every mistake is a treasure: Lessons learned from the TRIANGLE trial for anorexia nervosa.

Using the TRIANGLE trial as an illustrative case study, we highlight the value of lived experience and codesign for developing and testing interventions for AN. We offer several lessons learned over the course of the trial, pertaining to trial enrollment, retention and engagement, measurement of outcomes, and research adaptations for real-world settings, and hope that these recommendations facilitate future treatment research for AN.