How Borderline Personality Begins
Difficulties during the the seaparation stage of development pose a risk.
Updated May 4, 2026 | Reviewed by Hara Estroff Marano
This is part one of a two-part article. For part two on the borderline level of organization, click here .
People with borderline personality can cause significant chaos and pain to those around them. They can feel like chameleons, changing their colors against a variety of backgrounds. Their wild vacillations between adoration and disdain, between neediness and rage, can be confusing and overwhelming. But they are usually suffering terribly from feelings of emptiness and a pervasively unstable sense of self. How did these individuals develop such unstable relational patterns and difficulties with self identity?
Those whose personality is organized at a borderline level are preoccupied with dyadic relationships (child-mother) (Kernberg, 1975). Developmentally, such people run into significant challenges during the rapprochement period of the separation-individuation phase. During this subphase, at 16–24 months, children begin to experience themselves as separate from their mother ("mother" is shorthand for “primary attachment figure"), as they begin to more independently explore the environment (Mahler, Pine, Bergman, 1975).
The explorations, which a few months earlier were filled with omnipotent fantasies of safety and continued symbiosis with the perfect, protective mother, are now full of anxiety as the omnipotent fantasy wanes, along with a growing understanding that the child is not an extension of the mother and is therefore small and truly vulnerable to the dangers of the-world-away-from-mom (Mahler et al., 1975). There is a consequent ambivalence about both exploration and return: The child wants to explore the environment and expects a welcome reunion and also is easily frustrated by both the anxieties of exploration and the loss of autonomy that reunion with mom entails (Mahler et al., 1975). The child will periodically and anxiously return to mom during the exploration, seeking reassurance, safety, and joint attention in an effort to allay the child’s anxiety about the dangers of the world. In the next breath they are frustrated and upset to be too closely in mom’s orbit.
This phase of development is full of pitfalls for both mothers and children. For mothers who have their own dynamic needs to maintain symbiosis with their children, the efforts of the child to separate may be met with overattentive, suffocating enmeshment or anger and rejection at the “abandonment” of the mother by the child. Both reactions will greatly limit the child’s ability to separate successfully from the mother.
Many of these children are temperamentally highly sensitive and easily overstimulated. This constitutional sensitivity can lead to trouble separating despite a healthy response from the mother. Often it’s the combination of a child’s temperament and a mother’s own dynamic reaction to separation that leads to difficulties at the rapprochement phase (Mahler et al., 1975; Coonerty, 1986). When the child is unable to tolerate the anxiety of exploration or the mother unable to tolerate the child’s independence, the child cannot learn the critical developmental lesson that “the world is interesting but sometimes scary, and that’s okay because mom is waiting in the background to welcome me home when I’m ready for reassurance.”
A frequent failure at the rapprochement subphase happens when a child is free to explore (the mother doesn’t insist on symbiosis), but mom is not reliably available for the return. Such mothers are not sufficiently attuned or aware that the child needs to be able to come back to a physically and emotionally available mother when exploration becomes too stimulating or anxiety-provoking. The lack of a safe return leaves a child uneasy to begin the exploration in the first place.
In both situations, the child learns that abandonment (because of an unreliably available, clinging, or punishing mother) is too often the consequence of leaving the mother’s side. The child instead internalizes a fear of both physical independence and an independent sense of self. This leads to rage at the separation that now feels so dangerous (Mahler et al., 1975; Adler Buie, 1979).
The difficulties developing separateness from the mother lead to someone who is extremely uncertain about their sense of self. Because rapprochement is not successfully achieved, the child cannot internalize a complex, ambivalent version of her mother who can be both “good” (available, non-intrusive, attuned) and “bad” (sometimes unavailable, intrusive, or poorly attuned). The two ways of experiencing the mother are instead split into a “good mother” and “bad mother”. So the child does not develop what Mahler referred to as “object constancy”, an internalized view of the other who is the same across different conditions and emotional states (Mahler et al., 1975).
Since the two versions of the mother cannot co-exist, neither can a healthy self-representation, which in its most nascent stages is an internalization of the dyadic experience of child-with-mother (safe, nurtured) and mother-with-child (loved, enjoyed). So the child cannot experience herself as “good” (lovable and worthy) and “bad” (angry, needy, abandoned) simultaneously and instead must keep those self-representations separate—what Kernberg referred to as “identity diffusion” (Kernberg, 1975). Without a stable self-image across conditions and emotional states, the individual is left with feelings of emptiness, or hollowness.
Where a centered, consistent sense of personhood should be, there is instead a “candle in the wind”. There is a sense of panic about being alone because there is no stable soothing self (a product of an internalized mother who loves and enjoys the child). Instead of a stable core, there are wildly vacillating versions of the self: some grandiose and omnipotent like the infant who has not yet confronted the limits of separateness, some pathetic, unlovable, and abandoned like the internalized experience of the child with the rejecting, unavailable, or punishing mother (Adler Buie, 1979).
Importantly, issues at the rapprochement stage alone might not be sufficient to lead to a borderline organization. Given their high rates of occurrence, overt trauma , neglect, and abuse must be considered in any etiological explanation of borderline organization. A meta-analysis of 97 studies found that in case-control studies, individuals with BPD are nearly 14 times more likely to report childhood adversity than non-clinical controls, with emotional abuse and neglect showing the strongest associations (Porter et al., 2020).
Many theorists hypothesize that experiences of trauma and abuse also disrupt the internalization of an integrated “good and bad” mother, because of the common dissociative response to trauma and abuse; it disrupts and distorts integration of a coherent narrative of self-with-other (Luyten, Campbell, Fonagy, 2020), which reinforces the good/bad split of failed rapprochement. Neglect operates somewhat more insidiously, by creating the absence of an internalized loving, available mother.
Rapprochement failure and trauma are also bidirectional; mothers who are themselves victims of abuse are often too terrified or dissociated to provide the calm emotional availability and attunement necessary for resolution of the rapprochement phase, and abusive, neglectful mothers will not be able to successfully shepherd their child through this important but complex period. It is also clinically observed that for some children, successful rapprochement is followed by a trauma severe enough to fracture the internalized self-image, leading to borderline organization despite initial resolution of the rapprochement period.
Please see the following related posts:
Adler G, Buie DH. Aloneness and borderline psychopathology: the possible relevance of child development issues. International Journal of Psycho-Analysis. 1979;60(1):83-96.
Bora E. A meta-analysis of theory of mind and ‘mentalization’ in borderline personality disorder: a true neuro-social-cognitive or meta-social-cognitive impairment? Psychological Medicine. 2021;51(15):2541-2551.
Coonerty S. An exploration of separation-individuation themes in the borderline personality disorder. Journal of Personality Assessment. 1986;50(3):501-511.
Kernberg OF. Borderline Conditions and Pathological Narcissism. New York: Jason Aronson; 1975.
Kernberg OF. Severe Personality Disorders: Psychotherapeutic Strategies. New Haven: Yale University Press; 1984.
Mahler MS, Pine F, Bergman A. The Psychological Birth of the Human Infant: Symbiosis and Individuation. New York: Basic Books; 1975.
Porter C, Palmier-Claus J, Branitsky A, et al. Childhood adversity and borderline personality disorder: a meta-analysis. Acta Psychiatrica Scandinavica. 2020;141(1):6-20.
Stern BL, Caligor E, Hörz-Sagstetter S, Clarkin JF. An object-relations based model for the assessment of borderline psychopathology. Psychiatric Clinics of North America. 2018;41(4):595-611.
Winnicott DW. The use of an object and relating through identifications. International Journal of Psycho-Analysis. 1969;50:711-716.
Luyten P, Campbell C, Fonagy P. Borderline personality disorder, complex trauma, and problems with self and identity: a social-communicative approach. Journal of Personality. 2020;88(1):88-105.
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Irene Hurford, MD, is a psychiatrist and psychoanalyst with over 20 years of experience treating psychosis with both medications and psychotherapy.
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