A 25-year-old woman has a history of self-harm, intense unstable relationships, chronic emptiness, identity disturbance, and frantic efforts to avoid abandonment. She frequently uses splitting (seeing her therapist as 'perfect' then suddenly 'the worst ever'). What defence mechanism characterises borderline personality disorder, and what is the psychodynamic explanation for its use?

• A Reaction formation; transforms unacceptable impulses into their opposite
• B Intellectualisation; isolates the emotional component of distressing experience
• C Splitting; failure to integrate positive and negative attributes of self/other (part-object relations) due to developmental arrest in rapprochement phase of separation-individuation ✓
• D Projective identification; projects intolerable affects into others and then re-introjects them

Explanation

Splitting is the cardinal defence mechanism of borderline personality disorder. Kernberg's object relations theory attributes splitting to a developmental failure to integrate 'all-good' and 'all-bad' internal representations of self and object, due to arrest in Mahler's rapprochement phase. Because ambivalence (holding good and bad qualities simultaneously) cannot be tolerated, objects (people) are perceived as entirely good or entirely bad, shifting abruptly. This underlies the stormy relationships, idealisation-devaluation cycles, and identity diffusion. Projective identification — projecting an intolerable part-self into another while maintaining an emotional connection — is a related but distinct primitive defence also prominent in BPD.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.