Capturing the experience of borderline personality disorder symptoms in the daily lives of women with eating disorders

Borderline personality disorder (BPD) is highly comorbid with eating disorders (EDs), and comorbid ED-BPD is associated with a worse clinical presentation and treatment outcomes. Understanding how BPD symptoms manifest in the daily lives of those with EDs and predict momentary ED symptoms has important treatment implications. This study: (a) compared the nine BPD symptoms, assessed across 14 days, in individuals with comorbid ED-BPD, only an ED, and no ED; and (b) examined average and momentary relationships between BPD symptoms and specific ED symptoms (i.e., binge eating, purging, restriction, and maladaptive exercise) in women with EDs. Individuals with comorbid ED-BPD ( = 60), only an ED ( = 114), and controls ( = 47) completed 14 days of ecological momentary assessment. All BPD symptoms except affective instability were more common in individuals with comorbid ED-BPD than those with only an ED. Affective instability and paranoia/dissociation had the largest effect sizes, indicating the greatest differences across groups. Individuals with more frequent abandonment avoidance, anger, identity disturbance, paranoia/dissociation, and self-harm over the 14 days engaged in more frequent binge eating, while those with greater emptiness engaged in more frequent restriction and maladaptive exercise. Momentary affective instability predicted an increased likelihood of binge eating, while momentary interpersonal difficulties predicted a decreased likelihood of binge eating, at the next prompt. This study highlights the importance of considering BPD symptoms in the treatment of individuals with EDs to improve their clinical outcomes and quality of life. (PsycInfo Database Record (c) 2024 APA, all rights reserved).