Comorbidity of borderline with antisocial and narcissistic personality disorders: a multimethod study

The construct of borderline personality disorder (BPD) remains contentious, with some arguing that it embraces too much pathology to be of any real value as a clinical diagnosis. Examining BPD's comorbidity is key to understanding its heterogeneous vs. homogeneous nature.

This study aimed to uncover differences in patterns of symptoms and their severity between 3 groups of patients a with a DSM-5 diagnosis of BPD: (i) those with a single borderline diagnosis; (ii) those with a dual diagnosis of BPD and antisocial personality disorder (ASPD); those with a dual diagnosis of BPD and narcissistic personality disorder (NPD). Groups were compared in terms of: (i) borderline symptom severity; (ii) self-report measures of emotional dysregulation, suicidality, and identity disturbance; (iii) DSM-defined borderline symptom profiles. Network analysis assessed whether a stable and reproducible structure of symptoms could be seen across all three groups and whether groups differed in symptom prevalence.

Results of network analyses showed that the three groups shared the same symptom structure but differed systematically in which symptoms were most strongly endorsed: identity/interpersonal dysfunction in BPD, affective/behavioural dysregulation in BPD+ASPD, and a mixed/intermediate profile in BPD + NPD. BPD+ASPD showed the greatest severity of borderline symptoms, greatest emotional dysregulation, and highest impulsiveness and anger. The BPD group showed the highest identity disturbance and suicidality, BPD + NPD the lowest. In their symptom profiles, BPD were more likely to meet criteria for fear of abandonment, unstable relationships, identity disturbance and suicidality, while BPD+ASPD were more likely to meet criteria for impulsivity, affective instability, and anger control difficulty. The three groups differed on measures of identity and interpersonal relationships, supporting the idea that PD reflects disturbances of relationality.

Results highlight that BPD can manifest in different ways that depend on its comorbidity. These differences require treatment to be tailored to the individual patient, with a focus on identity/interpersonal dysfunction when BPD presents alone, and on affective/behavioural dysregulation when BPD co-occurs with ASPD.