Neuroadaptation and resultant habit-forming in anorexia nervosa patients is mediated by the dorsal frontostriatal circuits through repeated behavioral practice of food restriction. Initially, food is intentionally restricted as a means of attaining the positive reinforcement associated with planned weight loss. However, as the illness progresses, caloric restriction becomes automatic and requires little to no effort. Habit reversal therapy can  be utilized to reduce the strength of eating disorder habitual behaviors. 

Neuroadaptation in Severe and Enduring Anorexia Nervosa

Many patients with severe and enduring anorexia nervosa eventually develop an aversion to food, worsening resistance to treat. Patients may feel afraid of or disgusted by food due to developmental experiences such as bullying, but food aversion can also be worsened iatrogenically through traumatic or punitive feeding experiences that damage therapeutic relationships, such as restrained nasogastric feeding. Individuals with anorexia nervosa often have reduced capability for extinction of fear learning but increased fear generalization and reinstatement, especially among patients with comorbid depression. While exposure therapy is the standard for improving fear learning extinction, it can be problematic for anorexia nervosa patients as refeeding often entails weight gain, fluid shifts, and metabolic instability that may further reinforce the disorder's cognitions. Furthermore, the chronic stress of anorexia nervosa can reduce neurogenesis and therefore also reduce the efficacy of exposure treatments. Other treatments and supplementary measures for fear extinction are being explored, such as positive mood induction, cycloserine to consolidate learning, virtual reality therapy, cognitive remediation approaches that foster big-picture thinking, cognitive skills training for social avoidance, go/no-go inhibition training (especially for binge-purge subtypes), and food-related attention bias modification training.

Food Aversion in Severe and Enduring Anorexia Nervosa

Behavioral consequences of severe and enduring anorexia nervosa can further perpetuate the illness by creating additional barriers to recovery:

- Neuroadaptation/habit-forming
- Food aversion

Kalamazoo College

A model explaining the intra- and inter-personal maintenance factors for the continued duration of anorexia nervosa, not bound by Western sociocultural limitations. Intrapersonal factors combine to predispose individuals to anorexia nervosa and contribute to its maintenance, eliciting strong reactions from close others which then create interpersonal factors that further perpetuate the illness:

- Perfectionism/cognitive rigidity
- Experiential avoidance
- Pro-anorectic beliefs
- Expressed emotions

Cognitive-Interpersonal Maintenance Model of Anorexia Nervosa

Treasure, J., Willmott, D., Ambwani, S., Cardi, V., Clark Bryan, D., Rowlands, K., & Schmidt, U. (2020). Cognitive interpersonal model for anorexia nervosa revisited: The perpetuating factors that contribute to the development of the severe and enduring illness. Journal of Clinical Medicine, 9(3), 630. https://doi.org/10.3390/jcm9030630

Cognitive Interpersonal Model for Anorexia Nervosa Revisited: The Perpetuating Factors That Contribute to the Development of the Severe and Enduring Illness

Perfectionism or cognitive rigidity may serve as both a risk factor and a maintenance factor for anorexia nervosa. This includes obsessive-compulsive traits, all-or-nothing/black-or-white thinking, excessive attention to detail, and fear of making mistakes. In children, these traits lead individuals to be more influenced by societal rules and appearance norms, and thus more likely to develop obsessive-compulsive dieting behaviors once they have begun following a trigger event. Perfectionism and OCPD traits are associated with adverse outcomes for patients. Obsessive-compulsive spectrum disorders are present in 50% of ED patients, while other ED patients often have obsessive-compulsive or anxious traits. Obsessive thoughts and compulsive behaviors are often worsened as a result of starvation, leading to increasingly strict dieting rules.

Perfectionism/Cognitive Rigidity in Anorexia Nervosa

Anorexia nervosa patients are often temperamentally avoidant, displaying a sensitivity to negative stimuli, which 25% of anorexic individuals meeting criteria for avoidant personality disorder, including issues with intimacy, emotional expression, and identity. Intimacy and close relationships are often avoided in anorexia nervosa patients prior to onset of the disorder but avoidance is typically worsened following onset, making avoidant traits both a risk factor and maintenance factor for AN.
Experiential avoidance includes refusal to maintain contact with certain experiences/events and taking of measures to reduce their frequency/form/prerequisites. In anorexia nervosa patients, this may include repressing negative emotions and personal needs to cope with resultant stress. Patients are often shy, have few friends, avoid intimate relationships, and display psychosexual inhibition. They are also more likely to struggle to detect emotional signals from themselves and others, retrieve emotional autobiographical memories, and struggle with defensive emotions such as shame, guilty, and jealousy. Starvation worsens and is used as a mechanism for avoidance of emotions, relationships, etc.. Avoidant traits (low novelty seeking, high interpersonal distrust, anxiety disorders, avoidant-dependent personality disorder, OCPDs) are associated with poor outcomes and are common among anorexia nervosa patients, and thus treatments that focus on emotional processing rather than food and weight alone may show more success. 

Avoidance in Anorexia Nervosa

Pro-anorectic beliefs are perceived positive values of functions of anorexia nervosa or its symptoms. These beliefs often make patients reluctant to seek treatment or contribute to denial of the illness. In the early pre-contemplation stage of the disorder, patients perceive more positives than negatives to anorexia nervosa, but in the later action stage, the opposite is true. Some positives described by patients are that their disorder brings them feelings of safety, allows them to indirectly communicate distress, helps them to stifle negative emotions, and makes them feel special. While reducing pro-anorectic beliefs is associated with good outcomes, there is little data to support the relationship between pro-anorectic beliefs and outcomes, and its role as a maintenance factor is thus unclear.

Pro-Anorectic Beliefs in Anorexia Nervosa

Interpersonal factors like the intense emotional responses of close others may be a causal maintaining factor of anorexia nervosa, especially for patients with high levels of contact with their relatives. Expressed emotions (EE) measure criticism, hostility, and emotional over-involvement toward psychiatric patients from relatives, and high EE predicts relapse across numerous psychiatric illness. In cases of conflict with family members, anorexia nervosa patients may feel empowered by thwarting caregivers' attempts to intervene. This feeling of victory over logic and parental authority may reinforce beliefs and behaviors of anorexia nervosa by creating feelings of self-esteem derived from food restriction. On the other hand, excessive reassurance and support by caregivers may also reinforce the disorder by demonstrating that it elicits sympathy, care, and kindness, and may contribute to resentment toward the patient by other family members. High EE is thus correlated with distress among family members as they are unsure how to help and may have difficulty meeting other responsibilities outside of supporting the patient. For patients, having high EE relatives is associated with poorer outcomes, but these outcomes can be modified with family-based interventions. Some traits associated with anorexia nervosa are inherited, such as obsessive-compulsive traits and social impairment which can lead caregivers and family members to be excessively controlling or withdrawn toward the patient, contributing to inflexibility and miscommunication that can worsen the disorder. Instead, caregivers should focus on educating themselves about the nuances of anorexia nervosa's impacts on social cognition and communication, learning skills to support behavioral changes, and modeling a calm, compassionate, and collaborative environment. 

Expressed Emotions in Anorexia Nervosa

Certain factors predispose individuals to greater risk of anorexia nervosa:

- Negative self-evaluation
- Internalizing strategies
- Reduced social processing skills
- Increased sensitivity to social hierarchy,/negative judgements
- Desire to belong or be accepted based on social norms
- Internalized idealization of thinness

Predisposing Factors to Anorexia Nervosa

Anorexia nervosa creates a vicious cycle as many of the traits that contribute to the development and maintenance of the disorder are further worsened by malnutrition and starvation as the illness progresses. The starved brain is less plastic and is thus more resistant to treatment and less responsive to therapy. Furthermore, malnutrition further impairs set shifting, global integration, central coherence, and social cognition and communication. This leads anorexic individuals to become even more isolated and avoidant, and worsens obsessive-compulsive traits that perpetuate dieting behaviors. 

Secondary Consequences of Malnutrition in Anorexia Nervosa

Behavioral Consequences of Severe and Enduring Anorexia Nervosa

Chronic stress is at once a predisposing factor to, a result of, and a perpetuating factor of anorexia nervosa. It can result from genetic susceptibilities, developmental trauma, emotional abuse, or starvation. The chronic stress profile of treatment-resistant depression mimics that of anorexia nervosa, causing hyperactivity of the hypothalamic pituitary adrenal (HPA) axis, immune system activation, microbiome anomalies, reduction of neurogenesis and brain volume, and reduced hippocampal volume, which is also associated with increased cortisol levels, anxiety, and depression. This stress response impairs resilience and may cause reduced mesolimbic dopamine function, anhedonia, and decreased motivation, causing or worsening depression. 50% of anorexia nervosa patients report at least one mood disorder episode in their lifetime, and depression often persists regardless of fluctuations in eating disorder symptomatology. Depression is common about anorexic patients but they often present with fewer somatic symptoms (low energy, reduced neural activation) and more severe cognitive symptoms (negative self-image). Patients with a history of depression prior to onset of anorexia nervosa have been found to have reduced recovery rates, and those struggling with mood comorbidities likewise show worsened long-term outcomes. Anxiety traits, such as obsessive-compulsive personality traits, OCD, and anxiety disorders, are also common in childhood prior to onset of anorexia nervosa. Polygenic risk correlations with anorexia nervosa are strongest with OCD, followed by half-sized correlations with neuroticism, depression, and anxiety. Patients with severe and enduring forms of anorexia nervosa may thus benefit from treatments originally targeted towards treatment-resistant depression and OCD.

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