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.