Results of the LABILE trial showed no difference between people with BPD who were prescribed lamotrigine and those on placebo. However, most study participants experienced sustained improvement in their mental health during the trial. We conducted a thematic analysis of qualitative data from interviews with 47 LABILE study participants to identify factors that may have contributed to this improvement. We identified three main themes: initial reasons and expectations regarding trial participation, patients' experiences of the trial and areas of change. Reasons for participating in the trial included a search for consistent and stable professional care as well as altruistic motives. Improvements in symptoms over the course of the trial were explained by several factors including consistency provided by the research team, salience of the social context and the availability of alternative support networks. While participants appreciated the autonomy provided by the voluntary nature of the trial, they felt that improvements stemmed from the 'structure' brought about by their actively engaging in the study. This study highlights the importance of clear and transparent communication when treating people with BPD. Mental health professionals should ensure that services for people with BPD are consistent and structured. © 2019 John Wiley & Sons, Ltd.
© 2019 John Wiley & Sons, Ltd.