اختلالات حساسیت وابسته به انگیزش و تحریک درونی در زنان بهبودیافته از بولیمیا

Self-report studies suggest that patients with bulimia nervosa (BN) evidence difficulties with interoceptive awareness. Indeed, interoceptive deficits may persist after recovery of BN and may be a biological trait that predisposes symptom development in BN. However, no studies to date have directly assessed interoceptive sensitivity, or accuracy in detecting and perceiving internal body cues, in patients with or recovered from BN. Nine women who had recovered from BN and 10 healthy control women completed the Heart Beat Perception Task (HBPT) in which individuals were required to estimate the number of heartbeats between intervals of time. Accuracy scores were compared between groups. Significant differences were found between the groups on the HBPT ((F1,19) = 7.78, p = .013, Cohen's d = 1.16) when controlling for age. These results suggest that deficits in interoceptive sensitivity are present in individuals recovered from BN. Thus interoceptive deficits may be one factor that bridges the gap between brain dysfunction and symptom presentation in BN.

Bulimia nervosa (BN) is a serious psychiatric disorder that causes significant and costly medical problems. The financial costs associated with treating BN are high (Stuhldreher et al., 2012). BN also has one of the highest mortality rates of all psychiatric disorders, estimated to occur in 3.9% of cases (Crow, Frisch, et al., 2009 and Crow, Peterson, et al., 2009). Despite the fact that 1.5% of the population develops BN during his or her lifetime, mechanisms underlying symptom presentation in BN are poorly understood (Hudson, Hiripi, Pope, & Kessler, 2007). Evidence for the effectiveness of treatment for BN is accumulating (Brown & Keel, 2012), however, it remains important to improve the understanding of the psychophysiology of BN. New research, for example, suggests that BN has biological and genetic components (Hinney, Scherag, & Hebebrand, 2010), however, little research has been conducted to better understand the role that biological processes play in the development and maintenance of symptoms in BN. More research in this area is clearly required in order to develop better treatments and prevention strategies. Key symptoms that characterize BN are eating a large amount of food in a short period of time, the experience of a loss of control and the use of compensatory behaviors such as vomiting (American Psychiatric Association, 1994). Bruch was the first to suggest that such symptoms result from “disturbances in accuracy of perception or cognitive interpretation of stimuli arising from the body” (Bruch, 1962, p. 189). In the eating disorder field, these disturbances have been described as problems in interoceptive awareness (Garfinkel, Moldofsky, Garner, Stancer, & Coscina, 1978). Recently, interoceptive sensitivity has been studied and refers to “the ability to perceive consciously signals arising from the body” (Pollatos, Fustos, & Critchley, 2012, p. 1680). Disturbances in detecting and/or interpreting stimuli from the body, particularly hunger and satiety cues, could directly contribute to the development and maintenance of symptoms such as restrictive eating, binging and purging in BN. Difficulties in detecting and interpreting stimuli from the body could lead to misinterpretation of hunger and satiety cues. Binging and purging symptoms may reflect a difficulty in internally regulating misinterpreted hunger and satiety cues. Research on the neurobiological basis of interoception suggests that interoceptive processing occurs in several stages and follows a posterior to anterior physical progression in the insula cortex. Physiological cues involved in maintaining internal homeostasis are thought to be detected without conscious awareness in the posterior portion of the insula. Further, it has been suggested that interoceptive awareness occurs as these signals are processed into the anterior insula as an individual reflects upon his or her physical state (Craig, 2009). Numerous studies exploring various biological aspects of BN suggest that possible interoceptive deficits are involved in the development and maintenance of BN. For example, several studies have demonstrated that the threshold for detecting body cues in BN is higher than in controls; therefore, those with BN appear to require more intense stimuli in order to detect a baseline level of stimulation. These studies suggest that interoceptive deficits may be present and have examined pain processing, hunger, satiety, sensitivity to gastric distention, and taste detection in BN (De Zwaan et al., 1996, Geliebter and Hashim, 2001, Kissileff et al., 1996, Lautenbacher et al., 1991, Papezova et al., 2005, Rodin et al., 1990, Stein et al., 2003, Sunday and Halmi, 1990 and Zimmerli et al., 2006). Findings are consistent with neuroimaging studies in BN that have indicated decreased activation in both the posterior and anterior insula in those currently with BN (Bohon & Stice, 2011) and increased activation in the anterior insula in women recovered from BN (Oberndorfer et al., 2013). Therefore, interoceptive processing deficits may be related to abnormal functioning in interoceptive neural networks. Prior to this study, disturbances in interoception have been assessed in BN by a self-report measure (the Interoceptive Awareness scale on the Eating Disorder Inventory); results suggest that those with BN have lower scores than controls when measured by this subscale (Fassino et al., 2004, Lilenfeld et al., 2006, Pryor et al., 1996 and Taylor et al., 1996). However, to date, no studies have used an objective physiological measure to assess the biological aspects of interoception in BN, which is important for reliability and validity. And, although there are proposed physiological processes that are related to disturbed interoception in BN, no studies to date have directly assessed interoceptive sensitivity in BN. The gold standard task for assessing interoception deficits, and specifically interoceptive sensitivity, is the Heart Beat Perception Task (HBPT). The HBPT assesses one's accuracy in detecting and perceiving his or her heartbeats (Schandry, 1981). Individuals with anxiety disorders, particularly panic disorder, have shown increased accuracy in heartbeat detection whereas individuals with anorexia nervosa have demonstrated decreased accuracy in heartbeat detection (Domschke, Stevens, Pfleiderer, Gerlach, 2010; Pollatos et al., 2005). In healthy adults, studies have shown that accurate performance on the HBPT task activated both posterior and anterior regions of the insula (Pollatos et al., 2007, Pollatos et al., 2008 and Wiens, 2005). Additionally, HBPT scores have been shown to correlate with right insula volume in healthy adults (Critchley, 2005). The HBPT can be considered to measure one's ability to detect internal interoceptive stimuli without confounding by competing external stimuli such as in pain, gastric, and taste processing. In addition, the HBPT is simple to administer, and an EKG is the only piece of equipment needed to complete the task. This task can, therefore, be administered in clinical settings and in non-medical facility laboratories. In this study, women recovered from BN (BN-R) were studied in order to control the confounding effects of binge–purge symptoms. Physiological effects of active binging and purging include longer QTc intervals as measured on an EKG, changes in blood sugar levels, EEG abnormalities, abdominal and urinary disturbances, dental problems and inflammation of the esophagus (Peebles, Hardy, Wilson, & Lock, 2010). Physiological effects of active restricting, binging and purging, particularly EKG abnormalities, may confound one's ability to detect and perceive his or her heart beat. In order to understand the biological traits that may lead to the development of BN, we chose to study interoceptive sensitivity using the HBPT in BN-R. Interoceptive sensitivity in BN is important to study since directly measuring the interoceptive sensitivity of non-food related body cues in BN could help elucidate whether disturbances in interoception are due to intentional repression of food related body cues or organic global interoceptive deficits. Such disturbances in detecting and/or interpreting stimuli from the body, particularly hunger and satiety cues, could directly contribute to the development and maintenance of symptoms such as restrictive eating, binging and purging in BN. Therefore, interoception is important to study. We hypothesized that BN-R would display deficits on the HBPT task relative to healthy control participants, therefore, suggesting that interoceptive sensitivity deficits are present after symptom resolution in BN.

Overall, this study is significant since it provides valuable information about interoceptive sensitivity in individuals recovered from BN. Results suggest that individuals recovered from BN have significant deficits in interoceptive sensitivity as determined by low accuracy scores on the HBPT compared to healthy controls. Deficits in interoceptive sensitivity may explain binging symptoms seen in BN. As a result, this study justifies conducting additional research on interoceptive processing in BN.