Before Borderline Personality Disorder: A Narrative Review of Etiology and Developmental Integration

Background: Borderline personality disorder (BPD) is a prevalent and highly impairing condition whose origins cannot be explained by a single causal pathway. Contemporary research and theory inform a developmental view in which genetic, neurobiological, epigenetic, environmental, and psychological factors may interact recursively across time.Summary: This narrative review synthesizes evidence and theoretical perspectives on the origins of BPD across biological, epigenetic, environmental, social, psychological, and psychodynamic domains. Genetic and neurobiological findings point to polygenic vulnerability, heterogeneous fronto-limbic alterations, altered stress-response systems, and possible inflammatory and oxidative mechanisms. Epigenetic research examines possible biological embedding of adversity in stress-regulation, neuroplasticity, and neurotransmission pathways. Environmental evidence highlights associations with childhood adversity, invalidating caregiving, parental psychopathology, peer victimization, socioeconomic disadvantage, and cultural context. Psychological and psychodynamic models propose how temperament, maladaptive schemas, attachment disruption, emotion dysregulation, impaired mentalization, and fragmented self-other representations contribute to borderline pathology. Evidence is stronger for associations than for the causal sequences connecting these domains, and BPD specificity remains incompletely established. The review brings these accounts into a developmental synthesis, examining their convergence and differences and tracing proposed reciprocal relationships among biological vulnerability, caregiving and broader environments, psychological capacities, and subjective experience from infancy through adolescence.Key Messages: BPD can be understood within a framework of multiple interacting developmental pathways rather than a single cause. Equifinality, multifinality, and differential susceptibility provide perspectives on why different individuals may arrive at similar borderline presentations through distinct routes, while similar risk factors may lead to divergent outcomes. The synthesis translates these relationships into testable propositions about developmental sequences, reciprocal influences, protective processes, and what distinguishes borderline trajectories from other outcomes. It also informs individualized clinical formulation by connecting developmental vulnerabilities with current difficulties and available supports.