Moderating Factors for the Effectiveness of Brief Psychological Intervention for People With Probable Personality Disorder: Secondary Analysis of Data From the SPS Trial.

Brief interventions have been proposed as a means of increasing access to psychological treatment for people with personality disorder. However, evidence of their effectiveness is limited to date. A recent large-scale trial of Structured Psychological Support (SPS) for people with probable personality disorder showed little evidence of patient benefit. However, questions remain about whether shorter term psychological interventions may be suitable for some patients. We therefore conducted a secondary analysis of trial data to examine whether baseline level of personality dysfunction, duration of prior contact with mental health services and practitioner treatment sequence were associated with differential outcomes from SPS. Data from 336 participants recruited across seven NHS sites in England were analysed using multiple linear regression. We added interaction terms to examine moderation of treatment effects on social functioning and emotional dysregulation at 6 months. There was no clear evidence that practitioner treatment sequence influenced outcomes. There was also no strong statistical evidence that baseline personality dysfunction moderated treatment response, although exploratory analyses found weak evidence that SPS may be advantageous for emotional dysregulation among participants with lower levels of personality dysfunction. In addition, there was weak evidence that SPS was associated with improved social functioning among participants with shorter histories of contact with mental health services. Further research is needed to examine whether shorter term psychological interventions have a role for people with mild personality disorder or as part of early intervention pathways for people at an earlier stage of their contact with mental health services.