Post-traumatic stress disorder and the outcome of dialectical behaviour therapy for borderline personality disorder.

BACKGROUND: Individuals with borderline personality disorder (BPD) and comorbid post-traumatic stress disorder (PTSD) have a worse prognosis than individuals with BPD alone. A common view is that the emotional instability and impulsivity of BPD should be treated before attempting to address trauma. However, PTSD symptoms may interfere with patients' ability to benefit from such 'stabilizing' treatments.
METHODS: The effect of BPD-PTSD comorbidity on self-harm and BPD symptom outcomes was evaluated in 89 patients receiving dialectical behaviour therapy, using multilevel modelling.
RESULTS: Patients with comorbid BPD-PTSD showed a trend towards elevated BPD symptoms throughout the treatment year (β = 2.12, 95% CI = -0.21-4.44, p = 0.07). There was a three-way interaction between PTSD comorbidity, treatment completion and time, whereby PTSD comorbidity was associated with less reduction in self-harm frequency over time, but only in those completing the full 12 months of treatment (incident risk ratio = 1.16, 95% CI = 1.04-1.30, p < 0.01).
CONCLUSION: Patients with comorbid PTSD had a poorer outcome from dialectical behaviour therapy than those with BPD alone, possibly because of the negative impact of unaddressed trauma. The results provide further grounds for recently developed treatments targeting BPD traits and PTSD symptoms simultaneously.