Identifying moderating factors during the preschool period in the development of borderline personality disorder: a prospective longitudinal analysis

Background: Despite a growing literature detailing early childhood risk factors for borderline personality disorder (BPD), few studies have examined moderating factors that might mitigate or exacerbate the effects of those risk factors. The current study examined whether three preschool-age characteristics—impulsivity, emotional lability, and initiative-taking—moderated the relationship between known preschool-age risk factors and adolescent BPD symptoms. Methods: We performed multilevel modeling analyses in a sample (n = 151) from the Preschool Depression Study, a prospective longitudinal study with assessments from preschool through adolescence. Preschool risk factors included adverse childhood experiences, internalizing symptoms, and externalizing symptoms measured with parent clinical interviews. Preschool moderating factors were assessed via parent report and observational coding of temperament and behavior. The Borderline Personality Features Scale for Children measured BPD symptoms in adolescence. Results: We found that observed initiative-taking moderated the relationship between preschool internalizing symptoms and adolescent BPD symptoms (b = 0.57, p =.011) and moderated the relationship between preschool externalizing symptoms and adolescent BPD symptoms (b = 1.42, p =.013). Greater initiative-taking was associated with lower BPD risk for children with high internalizing or externalizing symptoms. Conversely, for children with low internalizing or externalizing symptoms, greater initiative-taking was associated with increased BPD risk. Conclusions: We identify a potential moderating factor in BPD development, offer novel targets for screening and intervention, and provide a framework for using early childhood observational assessments in BPD research. Our findings suggest the need for future research on early moderating factors in BPD development, which could inform early childhood interventions targeting those factors to mitigate the effects of potentially less malleable risk factors.