Dynamics Among Borderline Personality and Anxiety Features in Psychotherapy Outpatients: An Exploration of Nomothetic and Idiographic Patterns

Borderline personality disorder (BPD) involves instability in self-concept, emotions, and behavior. However, the dynamic, longitudinal relations among BPD symptoms and between these symptoms and other problematic emotional experiences are poorly understood. It is also unclear whether these dynamics are the same across persons (including across diagnostic boundaries), specific to individuals with BPD, or idiographic. The current study uses ecological momentary assessment and group iterative multiple model estimation, a novel, data-driven approach to identifying dynamic patterns in time-series data at group, subgroup, and individual levels, to investigate the dynamic connections among select features of BPD (anger, impulsivity, and identity disturbance) and anxiety-related experiences. Forty-two psychiatric outpatients diagnosed with BPD (n = 27) or with an anxiety disorder, but not BPD (n = 15), rated their anger, identity disturbance, impulsivity, anxiety, stress, and calmness states 6 times per day for 21 days, providing a total of 4,699 surveys. Only 1 dynamic link between symptoms was identified that applied at the group level, and group iterative multiple model estimation did not reveal stable subgroups of individuals with distinct symptom dynamics. Instead, these dynamics differed from individual to individual. These results suggest that connections among these BPD and anxiety symptoms do not depend on diagnosis and are somewhat idiographic. Case examples are used to illustrate the clinical utility of within-person symptom models as a supplement to traditional diagnostic information.