The biosocial developmental model of Borderline Personality Disorder (BPD) proposes that early vulnerability, indicated by behavioral and emotional dysregulation, is potentiated across development by environmental risk factors, culminating in BPD. However, empirical research pertaining to this hypothesis is lacking. The aim of this prospective cohort study was to determine whether dysregulated behavior in childhood is predictive of BPD symptoms in early adolescence; and whether this association is potentiated by negative parent or peer interactions.

The prospective sample consisted of 5711 children in the UK (ALSPAC). Dysregulated behaviour and emotions during the first 7 years of life were assessed and peer victimisation and parenting between 8 and 10 years of age. BPD was assessed at 11–12 years with the UK Childhood Interview for DSM-IV Borderline Personality Disorder (UK-CI-BPD); based on the borderline module of the Diagnostic Interview for DSM-IV Personality Disorders. Five or more BPD probable/definite symptoms were present in 7.3% of the population.

Stable dysregulated behavior, experience of harsh parenting and peer victimization during childhood predicted BPD symptoms at 11 years. However, the association between dysregulated behavior and BPD was entirely dependent on whether the child had experienced peer victimization but not on harsh parenting. Children who were highly dysregulated in their behavior, and victimized, experienced the highest levels of BPD symptoms.

Consistent with the biosocial developmental theory, trait dysregulation is potentiated across development by exposure to environmental risk: Peer victimization. Interventions targeting early dysregulated behavior or peer victimisation may reduce the development of BPD symptoms.