Trajectories, comorbidity, and risk factors for adolescent disordered eating and borderline personality disorder features.

PURPOSE: Borderline personality disorder (BPD) and eating disorders are highly comorbid, but the shared course of symptoms and associated risks remain poorly understood. The aim of this study was to examine joint symptom trajectories, temporal precedence, risk factors, and population attributable fractions (PAFs) in a community sample of adolescents, using a developmental psychopathology and psychosocial framework. METHODS: Across five years (age 14-18 years), adolescents (n = 544, 56% girls) reported on BPD features and disordered eating behavior. Sociodemographic, interpersonal, and clinical risks were assessed in childhood (age 10-13 years). We used a person-centered approach to examine latent class growth analyses, joint trajectory models, and calculated PAFs. RESULTS: Three-class solutions were found for both disordered eating and BPD features (low, moderate, high), creating nine joint trajectories. High levels of disordered eating were a stronger indicator of high levels of BPD features than was the reverse. Girls and LGBTQ+ youth were most likely to be in a high symptom trajectory. Bullying perpetration and clinical hyperactivity were unique risks for BPD features. Bullying victimization contributed the largest PAF to disordered eating and BPD features. CONCLUSION: We identified several novel and clinically relevant findings related to temporality, risks, screening, and the treatment of adolescent eating problems and BPD.