Sleep and affect in individuals with borderline personality disorder features: A daily diary study.

Given that people with borderline personality disorder (BPD) features are vulnerable to emotion dysregulation, they might be particularly sensitive to the emotional impacts of poor sleep quality and low sleep quantity. In the present study, we evaluated whether BPD features moderate the relationship between daily sleep, measured objectively (total sleep time [TST]) and subjectively (perceived sleep quality), and self-reports of positive and negative affect (NA). A sample of 83 cohabitating couples (n = 166) were recruited for a 3-week daily diary study. Participants completed a BPD symptom measure at baseline, a perceived sleep quality assessment each morning, and a daily emotion assessment each evening. TST was assessed daily using a FitBit activity monitor. Mixed-model regression analyses revealed a significant interaction between subjective sleep quality and overall BPD features in predicting daily levels of NA, even after statistical control of depression. Participants with higher BPD features exhibited greater NA on days when they reported worse sleep quality, as compared to participants with lower BPD features. Secondary analyses showed that this interaction seemed to be particularly impactful for anger, but not anxiety or sadness. In contrast, there was no significant interaction effect between BPD features and objectively assessed TST in predicting daily emotion. These results suggest that the emotional impact of poor subjective sleep quality might be more pronounced for those with BPD features. (PsycInfo Database Record (c) 2026 APA, all rights reserved).