Background
Bulimia nervosa (BN) and borderline personality disorder (BPD) are disorders that involve emotion dysregulation, for negative emotion in particular, as well as impulsive behaviors beyond binge eating and vomiting. Given these similarities in psychopathology, it is not surprising that those with BN also present with BPD in approximately one third of cases. Improved understanding of similarities and differences in the experience of negative and positive emotion could aid in the development of treatments specifically tailored to the needs of these disorders.
Methods
In this study, we examined Ecological Momentary Assessment (EMA) data from 133 women diagnosed with BN, 25 of whom also exhibited diagnostic levels of BPD. Emotions and behaviors were assessed daily, with multiple random and event-contingent signals to complete questionnaires on portable digital devices, for a period of two weeks.
Results
Results indicated that the BPD group experienced higher negative emotional variability on bulimic event days. Both groups also demonstrated increasing negative emotion and decreasing positive emotion pre- binge eating and vomiting, with levels of negative emotion decreasing and positive emotion increasing after, for both behaviors.
Conclusions
In terms of group differences, additive effects were found for the BN comorbid with BPD group, who demonstrated greater negative emotional variability, on bulimic event days, and also had higher overall levels of negative emotion pre- and post-binge eating. Those with BN only, however, displayed increasing trajectories of positive emotion before and after binge eating and after vomiting, indicating a potential emotional dampening effect of BPD.
Bulimia nervosa (BN) is a disorder involving frequent binge eating episodes, compensatory behaviors such as vomiting and laxative use to avoid weight gain, as well as self-concept dominated by shape and weight (APA, 1994). The health consequences of this disorder can be severe and include cardiovascular problems, electrolyte disturbances, and gastrointestinal disorders (Bulik et al., 2002). Furthermore, people with BN have high rates of personality disorders (Godt, 2008). Of those co-occurring personality disorder diagnoses, borderline personality disorder (BPD) is the most common, with comorbidity rates of around 30% (Cassin and von Ranson, 2005; Wonderlich and Mitchell, 1992). BPD is a chronic and severe disorder characterized by chaotic interpersonal relationships, emotional reactivity, anger control problems, identity diffusion, various forms of dysregulated behaviors, chronic feelings of emptiness, and self-injurious and suicidal behavior (APA, 1994). Given the severe and dysregulated nature of both disorders, more research is needed to understand how BN co-occurring with BPD may be different than BN alone.
1. Emotion dysregulation in bulimia nervosa and borderline personality disorder
Over the last decade research has identified that emotion dysregulation plays a major role in the propagation and maintenance of both BN and BPD symptomatology. Emotion dysregulation refers to the inability to control and modulate one's affective state to such a degree that emotions are experienced as out of control (Shedler and Westen, 2004). Interestingly, many people with BN exhibit emotional dysregulation and impulsive behaviors (beyond binge eating and vomiting), even without a simultaneous BPD diagnosis (Crosby et al., 2009; Myers et al., 2006). Emotional variability is one form of emotion dysregulation, where an individual will experience his or her emotions as fluctuating frequently, rather than being centered around a consistent average within-person level, and may be applied to both positive and negative emotion. For example, someone with high variability in emotion may experience elevated negative emotion in the morning, be euthymic in the afternoon, and then be upset again at night. Importantly, some studies have found a strong link between BPD and emotional variability (Koenigsberg et al., 2002; Henry et al., 2001).
Often understudied, in both BN and BPD, is the dysregulation or variability of positive emotion; different responses in positive emotion may be an important factor in distinguishing these disorders. For example, studies of BN have found increases in positive emotion following binge eating and vomiting (Smyth et al., 2007) and self-injury (Muehlenkamp et al., 2009). On the other hand, some studies have failed to find evidence of positive emotional variability in BPD (Klonsky, 2008; Selby et al., 2009). One potential reason for these different findings may be related to vomiting, which in those with BN may result in momentary elevations in positive emotion due to a sense of having “undone” the negative effects of binge episodes, a feeling of control, or maintaining progress toward a weight goal. This same experience of positive emotion post-binge eating and vomiting may not be as functionally reinforcing in individuals without high-level body weight and shape concerns.
Regardless of what may be causing emotional variability in these disorders, and differences in variability of positive and negative emotion, establishing qualitative and quantitative differences between those with BN and BPD, relative to those with BN alone, may provide a richer understanding of the different roots of behavioral dysfunction. One important implication of this comorbidity is the potential for an additive effect between the two disorders, where there are more frequent and intense experiences of negative or positive emotion due to the combination of problems regulating emotions and behavior, frequent concerns with interpersonal relationships, and weight/shape related stressors seen in individuals with both diagnoses. Furthermore, when both disorders are present, the underlying biological and cognitive vulnerabilities toward dysregulated emotion may work in an additive effect.
