Mentalizing on the edge: borderline traits and their association with real-time self-reflection - an ecological momentary assessment study

BACKGROUND: Mentalization plays a key role in borderline personality disorder (BPD), yet its moment-to-moment fluctuations remain understudied. This study is the first to use established self-report items within an Ecological Momentary Assessment (EMA) to explore the links between aspects of mentalizing in daily life and BPD traits in a community sample. METHODS: The non-clinical sample consisted of 86 participants (86% female) aged between 18 and 51 years (M = 22.93, SD = 5.36). As part of a baseline survey in the laboratory, the participants completed self-report questionnaires to assess borderline accentuation and mentalizing in the form of subjective certainty regarding their own and others' mental states (self-certainty and other-certainty). In addition, in a subsequent one-week EMA, they reported momentary self-certainty and other-certainty at six randomized times during the day. RESULTS: Using multiple regression (enter method), self-certainty proved to be a negative predictor of borderline accentuation, with intraindividual variations correlating positively with borderline personality style. Contrary to expectations, however, neither the level of other-certainty in the EMA nor the corresponding intraindividual fluctuations were related to borderline accentuation. CONCLUSION: Future studies should consider the high intraindividual variability of self- and other-certainty in order to obtain ecologically valid insights into mentalizing processes in the context of BPD. Promoting self-certainty may be a valuable target in BPD treatment. However, other-certainty might not be as important.