The statistical specificity of emotion dynamics in borderline personality disorder

Persons with borderline personality disorder (BPD) experience heightened emotional instability. Different components underlie instability, and the relation between instability and well-being could be confounded by average emotionality and within-person standard deviation across emotional states, reflecting variability. Therefore, the goal was to examine which pattern of emotion dynamics parsimoniously captures the emotional trajectories of persons with BPD. Forty persons with BPD, 38 clinical controls in a major depressive episode, and 40 healthy controls rated the intensity of their emotions 10 times a day for 1 week. After correction for differences in average emotionality, persons with BPD showed heightened emotional instability compared to both control groups. When additionally correcting for emotional variability, the authors found that instability indices did not differ between groups anymore. This shows that persons with BPD differ from control groups in the magnitude of emotional deviations from the emotional baseline, and not necessarily in the degree of abruptness of these deviations.