Stress-related fluctuations in personality functioning in daily life: Pilot data from an ambulatory monitoring study in outpatients diagnosed with borderline personality disorder

This pilot study aimed to test a comprehensive experience sampling method (ESM) protocol for investigating the relationship between stress and personality functioning (PF) in the daily lives of outpatients diagnosed with borderline personality disorder (BPD). Participants (N = 22) responded to a 32-item ESM questionnaire 10 times a day for 1 week while wearing two stress detection devices. Results showed that the protocol was feasible. There was a high level of compliance (i.e. average of 85%), and no serious adverse events. The main indices, that is, Stress and PF, demonstrated acceptable to excellent internal consistency and provisional evidence for their validity. We found that 64% of the variability in PF was due to within-subject differences. Mixed modelling showed that the momentary changes in stress (p < .001) and body position (i.e. active vs passive; p < .001) explained an estimated 46% of this within-subject variance. We found no significant within-subject effects when we used parameters of autonomic nervous system (ANS)–activity as predictors. Data loss during recording and artefact detection of electrophysiological data were substantial but not related to momentary changes in PF. The preliminary findings suggest that PF is a volatile aspect of personality pathology and that there is a strong, concurrent relationship between stress and PF in daily life. This pilot study constitutes the first demonstration of PF fluctuations within a clinical sample and initiates an examination of their association with ANS activity.