No evidence-based therapy for borderline personality disorder (BPD) exhibits a clear superiority. However, BPD is highly heterogeneous, and different patients may specifically benefit from the interventions of a particular treatment.

From a randomized trial comparing a year of dialectical behavior therapy (DBT) to general psychiatric management (GPM) for BPD, long-term (2-year-post) outcome data and patient baseline variables (n = 156) were used to examine individual and combined patient-level moderators of differential treatment response. A two-step bootstrapped and partially cross-validated moderator identification process was employed for 20 baseline variables. For identified moderators, 10-fold bootstrapped cross-validated models estimated response to each therapy, and long-term outcomes were compared for patients randomized to their model-predicted optimal v. non-optimal treatment.

Significant moderators surviving the two-step process included psychiatric symptom severity, BPD impulsivity symptoms (both GPM > DBT), dependent personality traits, childhood emotional abuse, and social adjustment (all DBT > GPM). Patients randomized to their model-predicted optimal treatment had significantly better long-term outcomes (d = 0.36, p = 0.028), especially if the model had a relatively stronger (top 60%) prediction for that patient (d = 0.61, p = 0.004). Among patients with a stronger prediction, this advantage held even when applying a conservative statistical check (d = 0.46, p = 0.043).

Patient characteristics influence the degree to which they respond to two treatments for BPD. Combining information from multiple moderators may help inform providers and patients as to which treatment is the most likely to lead to long-term symptom relief. Further research on personalized medicine in BPD is needed.

Borderline personality disorder (BPD) is characterized by a heterogeneous clinical phenotype that emerges from interactions among genetic, biological, neurodevelopmental, and psychosocial factors. In the present family study, we evaluated the familial aggregation of key clinical, personality, and neurodevelopmental phenotypes in probands with BPD (n = 103), first-degree biological relatives (n = 74; 43% without a history of psychiatric disorder), and non-psychiatric controls (n = 99).

Participants were assessed on DSM-IV psychiatric diagnoses, symptom dimensions of emotion dysregulation and impulsivity, ‘big five’ personality traits, and neurodevelopmental characteristics, as part of a larger family study on neurocognitive, biological, and genetic markers in BPD.

The most common psychiatric diagnoses in probands and relatives were major depression, substance use disorders, post-traumatic stress disorder, anxiety disorders, and avoidant personality disorder. There was evidence of familial aggregation for specific dimensions of impulsivity and emotion dysregulation, and the big five traits neuroticism and conscientiousness. Both probands and relatives reported an elevated neurodevelopmental history of attentional and behavioral difficulties.

These results support the validity of negative affectivity- and impulse-spectrum phenotypes associated with BPD and its familial risk. Further research is needed to investigate the aggregation of neurocognitive, neural and genetic factors in families with BPD and their associations with core phenotypes underlying the disorder.