Longitudinal Associations between Plasma Oxytocin Levels and Borderline Personality Disorder Symptoms in Adolescents

Background Borderline personality disorder (BPD) is a complex disorder associated with severe interpersonal instability and common relationship problems. Oxytocin has emerged as a candidate neuropeptide, with cross-sectional studies showing reduced levels in individuals with BPD. Longitudinal data – particularly in adolescents – remain scarce, leaving unresolved whether changes in oxytocin reflect treatment effects, developmental processes, or reciprocal influences with symptom trajectories. The present study examines the longitudinal associations of oxytocin and the number of fulfilled criteria for BPD diagnosis in adolescents. Methods We examined plasma oxytocin in adolescents who attended a specialized early intervention clinic for BPD. Individuals were assessed at baseline ( n = 239) and at one-year follow-up (n = 84). We tested for cross-lagged associations of plasma oxytocin and the number of fulfilled criteria for BPD diagnosis using structural equation modelling (SEM). Age, sex, estradiol levels, and scores of the Symptom Checklist were included as covariates. Results SEM showed a significant negative cross-lagged effect of oxytocin levels at baseline on BPD criteria at one-year follow-up, but no significant effect of BPD criteria on subsequent oxytocin levels. Conclusions The exploratory findings suggest that oxytocin may represent a potential biological correlate of future BPD symptom trajectories. A better understanding of the neurobiological processes underlying BPD may inform future treatment development. However, given the exploratory nature and methodological limitations of the present study, any clinical implication including the potential exploration of oxytocin-based lifestyle interventions remain preliminary and require replication before they can be translated into practice.