Abstract

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 & 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 (Klonksy, 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 a 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.

Emotional Impact of Dysregulated Eating Behaviors

Emotion regulation models of dysregulated eating behaviors suggest that binge eating and vomiting occur following increasing levels of negative emotion, and that the behavior results in a decrease in negative emotion (Selby et al., 2008). These functions are supported by numerous cross-sectional studies on binge eating and vomiting (Agras & Telch, 1998; Lynch et al., 2000) as well as longitudinal ecological momentary assessment studies (Anestis et al., 2010; Smyth et al., 2007). Binge eating and vomiting behaviors may help reduce experience of negative emotion by narrowing attention away from upsetting thoughts and focusing on the concrete physical stimuli associated with the binge eating (Selby et al., 2008).

Consistent with this conceptualization, Smyth et al. (2007) found that negative emotion increased and positive emotion decreased in the hours prior to a binge or purge in individuals with bulimia nervosa. Conversely, they also found that following the binge, levels of negative emotion decreased and positive emotion increased in these individuals. Thus, these findings point out that the potential for emotion regulating effect of binge eating and vomiting are still at issue, and that the emotion regulation functions of dysregulated eating behaviors may be acute and frequently followed by additional emotion dysregulation. Nonetheless, more empirical exploration of emotional states surrounding dysregulated eating behaviors is needed.

Binge Eating versus Vomiting

In general, trajectories of emotion prior to and after binge eating and vomiting have been studied with relatively the same expectations, increasing negative emotion before and decreased negative emotion afterward (Smyth et al., 2007). Yet, few studies have actually looked at potential differences in the quality of emotion surrounding these behaviors separately. Binge eating and vomiting are highly related behaviors, yet they are also fundamentally distinct and as such they may arise in response to different emotional experiences or exhibit differential effects on emotion post-behavior. So the emotional context of both binge eating and vomiting individual warrants further investigation.

Current Study

Various aspects of mood and behavior have been examined in eating disordered and personality disorder samples using ecological momentary assessment (EMA; Stone & Shiffman, 1994). EMA is a relatively new and innovative way to collect data that partially circumvents the limitations inherent to self-report measures, as it reduces retrospective recall bias while also allowing for assessment in a natural setting. A number of studies implementing EMA in the areas of eating disorders and BPD have been published in the past decade (Greeno et al., 2000; Le Grange et al., 2001; Russell et al., 2007; Trull et al., 2008; Wegner et al., 2002; Wonderlich et al., 2007). Although various aspects of emotion in samples of women with BN or BPD have been examined via EMA techniques, no studies to date have used EMA to investigate the emotion-behavior relationship for those with comorbid BN and BPD. The present study contrasts emotional responding surrounding binge eating and vomiting, in a sample of women with BN and no BPD diagnosis (BN) compared to women with BN and diagnostic levels of BPD (BN+BPD). We predicted that greater levels of emotional variability would be seen in the BN + BPD group than in the BN only group. This prediction was based on a broad array of reasons to experience emotion variability in the combined BPD + BN group (due to difficulty regulating emotions and impulsive behaviors, coupled with interpersonal concerns), but also because of potential underlying biological and cognitive dispositions to emotion variability in both disorders that may have an additive effect. Thus, for the present study, we hypothesized that those with BN+BPD, in comparison to those with BN alone, would have (1) greater daily variability in levels of negative emotion and positive emotion, (2) this effect would be even larger on days when bulimic events occurred, (3) increased trajectories of negative emotion and positive emotion preceding binge/vomit behaviors, and (4) increased trajectories of negative emotion and positive emotion following binge/vomit behaviors.

Methods

Participants were 133 adult females who were recruited from the community and who met criteria for BN (assessment procedure described below). Women were either referred for the study by their physicians, eating disorder treatment providers, or self-referred via community flyers. All completed a telephone screen to confirm eligibility prior to in-person assessment (i.e., inclusion criteria: female, age > 18, meets DSM-IV criteria for BN, no changes in mental health treatment in past 6 weeks). Participants were excluded from the study if they were: 1) male¹, 2) currently psychotic, 3) unable to read English at an 8^th-grade reading level, 4) positive for a history of gastric bypass surgery, or 5) had initiated psychotherapy or medication within the last six weeks. No participants were excluded based on type of purging method engaged in.

Baseline Assessment

EMA Signal and Event-Contingent Assessment Protocol

Procedures

The current research was approved by the Institutional Review Boards at the University of North Dakota and MeritCare Medical Center. During the baseline assessment, participants provided written informed consent and completed a baseline assessment to ensure eligibility. Next participants were trained in the use of a digital monitoring device (PalmPilot™ Vx). Participants then followed the assessment protocol for two days of practice, during which time they were asked to record just as they would during actual data collection.

Following the practice period, data were examined by study staff to confirm that they were input correctly (these practice data were not used in the subsequent analyses). Next, a 14-day data collection period began. During this time, participants were instructed to carry the device with them at all times, as they were prompted by random signal-continent recordings and event-continent recordings throughout the day (Wheeler & Reis, 1991). For each type of recording, participants were asked to complete ratings of their mood and behaviors. Signal-contingent recording prompted participants to complete mood ratings six times throughout the day when the portable digital device signaled them. The device signaled participants at a random following a stratified anchor blocks, and participants were to record data within 30-45 minutes of being signaled. In addition, event-contingent recording was employed as participants were asked to enter data whenever they engaged in eating disordered behaviors (e.g., binge eating, laxative use, etc.) or self-destructive behaviors (e.g., self-injury, drug abuse, etc.).

Upon completion of data collection, participants returned the device and their data were reviewed by study staff with the participant present to ensure that any potential confusion with recordings could be addressed and clarified by the participant. Participants received $100 for each week that they recorded data on the portable digital device and those participants who responded to 85% of the signal-contingent prompts within 45 minutes were given an additional $50 bonus.

Set 1: Daily Emotional Variability
                Level 1: (PEij or NEij) = β0j + β1j(Bulimic Event Day)ij
                Level 2 (individual): β0j = γ00 + γ01(Group)j + u0j
                                      β1j = γ10 + γ11 (Group)j
                Reduced Equation: (daily PEij or NEij) = γ00 + γ10(Bulimic Event Day)ij +
                                   γ01(Group)j + γ11(Group*Bulimic Event Day)j + u0j


Set 2: Momentary Emotional Trajectory Models Pre- or Post-, Binge eating or Vomiting
        Level 1: (PEij or NEij) = β0j + β1j(Time)ij + β2j(Time2)ij
        Level 2 (individual): β0j + γ00 + γ01(Group)j + u0j
                              β1j = γ10 + γ11(Group)j
                              β2j = γ20 + γ21(Group)j
                              β3j = γ30 + γ31(Group)j
        Reduced Equation: (daily PEij or NEij) = γ00 + γ10(Time)ij + γ20(Time2)ij +γ01(Group)j +
                          γ11(Group*Time)j + γ21(Group*Time2)j + u0j

Results

Discussion

BN and BPD are disorders that are frequently comorbid and they share many similarities in emotion dysregulation and impulsive behavior. The purpose of this study was to establish differences in overall emotional variability and emotional responses before and after binge eating and vomiting between those with BN and comorbid BPD. Using data from an EMA study, we compared women with BN and no BPD diagnosis (BN-BPD) to those with BN and comorbid BPD (BN+BPD) on variability of negative and positive emotion, and on emotional trajectories before and after binge episodes and vomiting episodes. Contrary to our expectations, those with BPD did not exhibit overall increased emotional variability relative to those without. For both groups, negative emotional variability was also elevated on eating disorder event days, suggesting that emotional variability may have contributed to binge eating and/or vomiting. There was, however, a significant interaction where those with BPD experienced greater negative emotional variability on bulimic event days than those without BPD, supporting our second hypothesis. On the other hand, those without BPD (BN-BPD) actually exhibited significantly higher levels of positive emotion variability in general, with no differences in eating disorder event days or group interaction.

Concerning our third and fourth hypotheses, negative emotion prior to a binge was elevated for the BN+BPD group relative to the BN-BPD group, however, there were no significant group differences in increases of positive emotion as a function of time leading up to binge episodes. Following the binge episode, both groups demonstrated elevations in negative emotion as a function of time, but there were no significant group differences in magnitude of negative emotion or group interaction with time predicting higher increases in negative emotion. Regarding negative emotion surrounding vomiting, both groups demonstrated increasing negative emotion before, and decreasing negative emotion after, however there were no significant group differences or group by time interactions. In terms of positive emotion, before and after binge episodes those with BN only demonstrated steeper trajectories with positive emotion decreasing more prior to a binge and showing a larger increase after a binge than those with BPD. On the other hand, there were no differences in trajectory of positive emotion prior to a vomit episode, although both groups demonstrated decreasing positive emotion. After binge episodes there was a significantly steeper trajectory of positive emotion for those with BN only, as indicated by a significant group by time interaction.

Overall, these findings provided some support for our hypothesized additive effect between BPD and BN, and were consistent with the above findings of high emotional variability on bulimic event days in this group. The comorbid condition of BPD and BN may result in an additive higher set point of overall negative emotion, but with both groups experiencing similar variability of negative emotion. However, those with BPD may experience elevated negative emotional variability on days with binge and vomit episodes. Regarding positive emotion variability, we found that contrary to expectations those with BPD experienced less positive variability than those without, when we expected more. These findings on positive emotion indicate that the presence of a BPD diagnoses may actually dampen trajectory of positive emotion in BN, rather than amplify it, and are consistent with other findings that those with BPD may not display increase reactivity of positive emotion (Selby et al., 2009). This finding also leaves to question whether there are problems with variability of positive emotion in BN, and whether potential dysregulation of positive emotion may further contribute to symptoms in the BN group that lacks BPD comorbidity. Perhaps an important function of dysregulated eating behaviors in BN may be increasing positive emotion, in combination with reducing negative emotion, rather than in comorbid BN and BPD where such behaviors may be primarily to escape negative emotion.

Given the enhanced understanding of emotional variability and emotions surrounding eating disordered behaviors in comorbid BPD and BN, there may be an opportunity to enhance current treatments for BN and BPD. For example, dialectical behavior therapy (Linehan, 1993) is a therapy traditionally used to treat BPD, but recent studies have found that it also has promising potential for the treatment of BN (Safer, Telch, & Agras, 2001). Based on the findings of the current study, DBT may also be a promising intervention to tail to those with comorbid BN and BPD, and important focuses of treatment may focus less on suicidal, self-injurious, or substance use behaviors and instead on eating behaviors such as binging and purging. Modifications might also include examining the potential triggers that elicit negative and positive emotion, to further elucidate if triggers tend to be more interpersonal/situational or weight/shape related. In addition, the specific modules of DBT might be enhanced to focus on eating specific problems, such as focusing on distress tolerance when experiencing concerns about body image. Finally, developing better emotion regulation skills and recognizing that days with worse negative emotion are associated with elevated eating disordered behaviors may help patients with both disorders develop better understanding of how their emotions may influence their behaviors.

There are some limitations to note with the current study. First, because this study did not have a BPD only comparison group, it is difficult to determine if the findings of those with BN and BPD in this sample are due to the comorbidity, or if these effects were primarily driven by BPD. Given BPD is a diagnosis driven by emotional variability, it the presence of this diagnosis alone may have accounted for the effects. This is unlikely, however, given that no main group effect was observed on negative emotional variability. Furthermore, since we controlled for presence of another Axis I disorder besides BN, it is unlikely that comorbidity in general accounted for this effect. Second, BPD diagnosis was made using a cut-off score on the DIB-R. A structured clinical interview for diagnosis of BPD would have been the preferred method for establishing diagnostic validity, although the method used in this study was fairly conservative and consistent across measures of BPD symptoms. However, we used a more conservative measure of BPD symptoms, which ameliorates this concern to some extent. Furthermore, we used BPD diagnosis in analyses for this study to help delineate differences in emotional patterns for comorbid BN and BPD, when use of a dimensional measure of BPD symptoms may have yielded somewhat different results. Another potential concern is that women who were pregnant were not excluded from participating in this study, and we did not maintain records as to whether participants were pregnant or not, so we are unable to empirically examine the impact of pregnancy on our findings. Although it is possible that some participants may have been pregnant, we expect that this would have been only a small minority of participants and would be unlikely to have influenced the result in a major way. However, pregnancy in those with BN could certainly influence the experience of binge episodes and emotional experiences. Finally, data monitoring may have introduced some level of reactivity in the participants, and thereby influenced their ratings or even overall emotional awareness.

Despite these limitations, this study is one of the first to provide an in-depth examination of pathological emotional processes in comorbid BN and BPD. Future studies should examine the potential emotion regulation effects of purging behaviors besides vomiting, and examine if those with comorbid BPD and BN exhibit similar emotional trajectories before and after these behaviors as well, and findings should be replicated in males with BN and BPD. Future studies should also examine scenarios where more than one behavior occurs in the same time frame (i.e. a binge episode along with a self-injury episode) to determine if there are differences in emotional responding relative to when a single behavior occurs. Although the overall pattern of findings in this study was unlikely influenced by simultaneous behaviors occurring along with binge and vomiting episodes, examining the emotional responding surrounding instances of multiple behaviors is an important direction for future research. Such research may enhance our understanding of the emotion regulation function of such behaviors occurring in close proximity to each other. Furthermore, those with BPD and BN should be compared to a group of those with BPD only. Doing so may provide further evidence of an additive effect or it may provide evidence that, as in positive emotion, BPD may simply mask the negative emotional responding of those with BN.

Footnotes

Contributor Information

Edward A. Selby, Rutgers University.

Peter Doyle, The University of Chicago.

References