Effectiveness and cost-effectiveness of dialectical behaviour therapy for self-harming patients with personality disorder: a pragmatic randomised controlled trial.

BACKGROUND

A primary goal of dialectical behaviour therapy (DBT) is to reduce self-harm, but findings from empirical studies are inconclusive. The aim of this study was to assess the effectiveness and cost-effectiveness of DBT in reducing self-harm in patients with personality disorder.

METHODS

Participants with a personality disorder and at least 5 days of self-harm in the previous year were randomised to receive 12 months of either DBT or treatment as usual (TAU). The primary outcome was the frequency of days with self-harm; secondary outcomes included borderline personality disorder symptoms, general psychiatric symptoms, subjective quality of life, and costs of care.

RESULTS

Forty patients each were randomised to DBT and TAU. In an intention-to-treat analysis, there was a statistically significant treatment by time interaction for self-harm (incidence rate ratio 0.91, 95% CI 0.89-0.92, p < 0.001). For every 2 months spent in DBT, the risk of self-harm decreased by 9% relative to TAU. There was no evidence of differences on any secondary outcomes. The economic analysis revealed a total cost of a mean of 5,685 GBP (6,786 EUR) in DBT compared to a mean of 3,754 GBP (4,481 EUR) in TAU, but the difference was not significant (95% CI -603 to 4,599 GBP). Forty-eight per cent of patients completed DBT. They had a greater reduction in self-harm compared to dropouts (incidence rate ratio 0.78, 95% CI 0.76-0.80, p < 0.001).

CONCLUSIONS

DBT can be effective in reducing self-harm in patients with personality disorder, possibly incurring higher total treatment costs. The effect is stronger in those who complete treatment. Future research should explore how to improve treatment adherence.