Brief individual psychological intervention for people with probable personality disorder::a multicentre, randomised controlled superiority trial in England.

<b>Background</b> Long-term psychological treatments are recommended for people with personality disorder. Brief interventions are increasingly delivered but of uncertain benefit. We aimed to investigate the effectiveness of a brief individual psychological intervention for people with probable personality disorder over a 12-month period. <br/><br/><b>Methods</b> The Structured Psychological Support (SPS) study was a multi-centre, researcher-masked, randomised controlled superiority trial, conducted in seven mental health Trusts in England. Participants were 18 years or older and had probable personality disorder identified by meeting a threshold of four or more on the Standardised Assessment of Personality Abbreviated Scale. We excluded those who: did not consent; had a co-existing psychosis; or were already receiving psychological treatment. We assessed whether participants met criteria for borderline personality disorder using the Structured Clinical Interview for Axis II Personality Disorders and whether they had co-existing Complex Post Traumatic Stress Disorder using the International Trauma Questionnaire. <br/>We randomised participants to up to 10 sessions of SPS or enhanced treatment as usual (allocation ratio 1∙15: 1), using an independent remote system. Researchers assessing outcomes were masked to group allocation. SPS comprises of up to 10 individual sessions of personalised psychological support, which includes psychoeducation and psychological skills derived from evidence-based treatments (Dialectical Behaviour Therapy and Mentalization Based Treatment). Sessions were usually delivered on a fortnightly basis by staff with previous experience of working with people with personality disorder who had completed three, three-hour training sessions and received fortnightly supervision from experienced supervisors. The primary outcome was social functioning at 12 months measured using the Work and Social Adjustment Scale. Data were analysed using multilevel mixed effects general linear regression on an intention-to-treat basis. We undertook a parallel health economic evaluation, which included a cost-effectiveness and cost-utility analyses. People with lived experience were involved in the design of the research and in the writing process. The trial was prospectively registered (ISRCTN13918289) and is now complete<br/><br/><b>Outcomes</b> Between 7th February 2023 and 31st January 2024, 569 people were screened. Of these, 336 were allocated to the active arm (180) or control arm (156) of the trial. Most participants were female (n = 257, 75, %), 75 (22%) were men and 10 (3%) were transgendered or non-binary. Mean age was 34.8 (Standard Deviation = 13∙2), and 281 (77%) were white. The attrition rate was 15% at 12 months. There was no difference between groups on the primary outcome (Coefficient = 0∙12, 95% CI = -2∙1, 2∙4, p = 0∙91). The probability that SPS is cost effective was between 34-39%. There were 36 serious adverse events affecting 17 participants in the active and 16 in the control arm of the trial. None were judged to be related to study procedures.<br/><br/><b>Interpretation</b> We found no difference in social functioning over one-year among people offered brief psychological intervention and no evidence of cost-effectiveness. These data highlight the importance of improving access to longer-term evidence-based psychological treatment programmes for people with personality disorder.<br/>