[Comment] From mirror to mind: body dissatisfaction and mental health

One of the enduring challenges in mental health research is disentangling environmental from genetic influences. Drawing on longitudinal data from the UK-based Twins Early Development Study, in The Lancet Psychiatry, Ilaria Costantini and colleagues1 convincingly address this challenge and make a major contribution to understanding how adolescent body dissatisfaction might shape trajectories of mental health and bodyweight. Their combination of phenotypic, twin-difference, and twin-modelling analyses provides a methodologically rigorous approach to this complex question.