Interoceptive Mechanisms of Body Image Disturbance in Anorexia Nervosa

Anorexia nervosa (AN) accounts for more than 10,000 deaths per year in the United States alone, marking it as a psychiatric disorder with one of the highest standardized mortality rates. Current AN treatments have only moderate efficacy and result in relapse rates as high as 50% within one year of hospitalization. A poor understanding of the pathophysiology of AN, particularly the core diagnostic feature of body image disturbance (BID), has hindered treatment development. Abnormal interoceptive processing (i.e., internal body signal) has been proposed to contribute to BID and a mechanistic delineation of the association between interoception and BID could lead to novel interventions for AN. This proposal uses a behavioral experimental therapeutics approach to determine how modulating interoceptive processing affects BID in AN.

Body image, defined as the multifaceted experience of one's physical appearance, is comprised of cognitive, affective, and perceptual components. BID is a key diagnostic feature of AN that is associated with poor outcomes, including relapse following hospital discharge. It is slow to improve in women with AN, and has been consistently identified as a factor contributing to the persistence of AN symptoms and relapse following treatment.

Perceptual BID is a complex and poorly understood facet proposed to involve the integration of body-related visual signals with representations of interoceptive signals. Studies indicate women with AN overestimate their body size. Standard of care treatments for AN, such as Cognitive Behavioral Therapy, focus on modifying the cognitive/affective components of BID but rarely address the perceptual component, making it an under-investigated therapeutic target.

Diminished sensitivity to interoceptive body signals in AN may lead to an overreliance on exteroceptive (i.e., visual) body-related signals, which in turn, is likely to facilitate self-objectification (seeing one's body as an object). The outcome of this process is an inaccurate representation of physical body characteristics (i.e., perceiving one's body as larger than its true size) despite continuing to focus on it excessively. To explore whether the modulation of interoceptive signaling could improve perceptual BID in AN, we recently utilized a non-pharmacologic intervention called floatation-REST (Reduced Environmental Stimulation Therapy). During floatation-REST, input from visual, auditory, olfactory, gustatory, thermal, tactile, vestibular and proprioceptive channels are minimized, and interoceptive input is enhanced. Across two clinical trials in AN we have found that floatation-REST acutely reduces perceptual BID, indexed by the body dissatisfaction score on the Photographic Figure Rating Scale (PFRS), after one session and reliably after multiple sessions.

Acceptance and commitment therapy (ACT) for eating disorders and body image has been examined previously and evidence supports the reduction of cognitive/affective BID symptoms. The proposed study will combine floatation-REST with interoceptively focused acceptance- and mindfulness-based components (interoceptively focused therapy [IFT]). The primary purpose of the proposed study is to examine the acute synergistic effects of IFT and float on BID. Further, the proposed study will be the first to systematically examine associations between BID and interoception using multiple levels of analysis (i.e., self-report and behavioral assays and neuroimaging) and combine them with perturbations of interoceptive and cognitive processing to examine the impact of interoception on perceptual BID. All participants will receive a one-hour introduction session prior to being randomized on a 1:1 basis to receive three 45-minute floatation-REST sessions (to attenuate exteroceptive input and enhance interoceptive input) paired with IFT or three 45-minute self-guided exteroceptive practice sessions (active comparator to enhance cognitive/affective BID, EFT group). During the IFT/EFT sessions the skills presented have been matched as closely as possible with the exception of the focus. For example, both groups engage in contact with the present moment exercises. In the IFT group, the focus is internal body sensations; whereas in the EFT group, the focus in the experience outside the individual (e.g., their environment sights, sounds, etc). While ACT is typically conducted in longer intervals (10+ weeks of 1 hour sessions), there is growing evidence to support the potential of briefer ACT interventions.

Both groups will complete behavioral and self-report assays of interoception, perceptual and cognitive/affective BID, and state/trait illness measures pre- and post-experimental session; pre and post intervention measures including self-report, behavioral, and neurobiological assays (specifically functional magnetic resonance imaging); and longitudinal follow-ups. The ability to reliably improve BID marks a step forward in the search for more effective BID treatments for AN. Given that it is expected that acceptance and mindfulness-based components will impact affective components of body image, it is expected that there will be an additive effect on the primary outcome (perceptual BID).

Inclusion criteria

• Primary diagnosis of anorexia nervosa
• Photographic Figure Rating Scale (PFRS) body dissatisfaction score greater than or equal to 1
• Eating Disorder Examination Questionnaire (EDE-Q6) Shape Concern Subscale score greater than or equal to 3
• Weight restored to body mass index (BMI) greater than or equal to 17.5
• No current evidence of orthostatic hypotension or if there is no evidence of additional fall risk as determined by their provider
• Clinical status transition from acute to residential status
• No new psychiatric medications in the week prior to randomization
• Female sex assigned at birth
• Ages 13 to 50 years
• Independently ambulatory
• Ability to lay flat comfortably
• English proficiency
• Willingness and ability to participate in study procedures
• Provision of informed consent (parent consent and minor assent if less than 18 years of age).

Exclusion criteria

• Active suicidal ideation with plan and intent
• Active cutting or skin lacerating behaviors
• Pregnancy as defined by urine screening
• Acute intoxication as indicated by urine drug screen or breathalyzer
• Orthostatic hypotension as determined by medical provider, evidenced in chart (defined as a drop of ≥ 20 mmHg in systolic blood pressure (BP) or a drop of ≥ 10 mm Hg in diastolic blood pressure (BP) when measured shortly after transitioning from lying down to standing). If evidence of orthostasis is present in chart consultation with provider to determine if status creates additional fall risk. If participant is determined to be at increased fall risk (e.g., dizziness upon standing) they will be excluded.
• Seizure reported within the previous 12 months
• Co-morbid diagnoses of Diagnostic and Statistical Manual of Mental Disorders, 5th ed. (DSM-5) bipolar disorder, schizophrenia, or other psychosis spectrum disorder
• Systolic blood pressure > 160 mmHg
• Diastolic blood pressure >100 mmHg
• Resting heart rate <50 beats per minute.