Effectiveness and safety of the adjunctive use of an internet-based self-management intervention for borderline personality disorder in addition to care as usual: Results from a randomised controlled trial

Importance Borderline personality disorder (BPD) is a severe mental disorder that is often inadequately treated. Objective To determine if adding a self-management intervention to care as usual (CAU) is effective and safe. Design Randomised, controlled, rater-blind trial. Duration of treatment and assessments: 12 months. Setting Secondary care, recruited mainly via the internet. Participants Patients with BPD and BPD Severity Index (BPDSI) of at least 15. Interventions CAU by treating psychiatrist and/or psychotherapist alone or adjunctive use of an internet-based self-management intervention that is based on schema therapy (priovi). Main outcome measure Outcomes were assessed by trained raters. The primary outcome was change in BPDSI. The safety outcome was the number of serious adverse events (SAEs). The primary outcome time point was 12 months after randomisation. Results Of 383 participants assessed for eligibility, 204 were included (91.7% female, mean age: 32.4 years; 74% were in psychotherapy and 26% were in psychiatric treatment). The slope of BPDSI change did not differ significantly between groups from baseline to 12 months (F 3,248 = 1.857, p=0.14). At 12 months, the within-group effect sizes were d=1.38 (95% CI 1.07 to 1.68) for the intervention group and d=1.02 (95% CI 0.73 to 1.31) for the control group. The between-group effect size was d=0.27 (95% CI 0.00 to 0.55) in the intention-to-treat sample and d=0.39 (95% CI 0.09 to 0.68) for those who used the intervention for at least 3 hours (per-protocol sample). We found no significant differences in SAEs. Conclusions We have not found a significant effect in favour of the intervention. This might be due to the unexpectedly large effect in the group receiving CAU by a psychiatrist and/or psychotherapist alone. Trial registration NCT03418142.