A reward-centred model of anorexia nervosa: A focussed narrative review of the neurological and psychophysiological literature

Reduced contextual influence on decision conflict during delay discounting persists after weight-restoration in anorexia nervosa

Prior research has investigated whether the capacity of individuals with anorexia nervosa (AN) to forgo food rewards in their pursuit of thinness may manifest as more delayed gratification in delay discounting tasks, but results have been mixed. In a previous study examining mouse-cursor movement trajectories during a delay discounting task, underweight patients with AN made similar decisions relative to healthy controls, but displayed more stable levels of decision-making conflict. Here, we employed the exact same methods to test whether these changes persist after long-term weight restoration. We recorded mouse-cursor trajectories during a delay discounting task in 45 female adolescents and young women weight-restored from AN (wrAN) and 90 female healthy controls (HC). We examined group differences in deviations from a direct choice path as a measure of decision-making conflict strength and moderation effects of associated predictors (e.g., choice difficulty). No group differences were detected in either delay discounting parameters or mouse cursor trajectories, and the effect of the aforementioned predictors on deviations was reduced in wrAN relative to HC. Persisting reduced variability of conflict strength across decisions might reflect a cognitive-behavioral trait marker of AN. This may enable individuals with AN to pursue long-term (body-weight) goals, because particularly conflicting choices may not be experienced as such.

Restrained Eating Features and Brain Morphology: A Pediatric Population-Based Study

OBJECTIVE

Anorexia nervosa, a restrictive eating disorder that is most commonly seen in females, is associated with alterations in gray matter (GM) and white matter (WM) structures. However, little is known about how restrained eating (RE) and the body mass index-standard deviation score (BMI-SDS) are related to brain morphology and whether sex differences exist in the general pediatric population.

METHOD

Participants were 9-year-old girls and boys (n = 2729) from the population-based Generation R Study. BMI-SDS was calculated by adjusting BMI for sex and age, using Dutch growth curves. RE is measured with the Dutch Eating Behavior Questionnaire. All children underwent structural magnetic resonance imaging, and brain volumes were calculated using FreeSurfer.

RESULTS

BMI-SDS in girls was positively associated with total intracranial volume and several regional brain volumes. In addition, BMI-SDS showed an inverted U-shaped association with total GM and WM. In girls, RE had a positive linear association with total intracranial, WM, and several regional brain volumes, corrected for BMI-SDS. Additionally, there was an inverted U-shaped association with the amygdala and insula volume. In boys, we found merely positive linear associations between BMI-SDS and brain volumes, and no associations between RE and brain volumes.

DISCUSSION

Associations between BMI and brain volumes exist in typically developing children, but there are significant sex differences in the magnitude and shape of the associations. RE is associated with some differences in brain volumes in girls only. Longitudinal studies are needed to assess these associations over a longer period of time.

Eating disorder symptoms and emotional arousal modulate food biases during reward learning in females

Food seeking and avoidance engage primary reward systems to drive behavior. It is nevertheless unclear whether innate or learned food biases interact with general reward processing to interfere with goal-directed choice. To this end, we recruited a large non-clinical sample of females with high eating-disorder symptoms ('HED') and a matched sample of females with low eating-disorder symptoms ('LED') to complete a reward-learning task where the calorie content of food stimuli was incidental to the goal of maximizing monetary reward. We find and replicate a low-calorie food bias in HED and a high-calorie food bias in LED, reflecting the strength of pre-experimental food-reward associations. An emotional arousal manipulation shifts this group-dependent bias across individual differences, with interoceptive awareness predicting this change. Reinforcement-learning models further identify distinct cognitive components supporting these group-specific food biases. Our results highlight the influence of reinforcement-based mechanisms and emotional arousal in eliciting potentially maladaptive food-reward associations.

Exaggerated frontoparietal control over cognitive effort-based decision-making in young women with anorexia nervosa

Effortful tasks are generally experienced as costly, but the value of work varies greatly across individuals and populations. While most mental health conditions are characterized by amotivation and effort avoidance, individuals with anorexia nervosa (AN) persistently engage in effortful behaviors that most people find unrewarding (food restriction, excessive exercise). Current models of AN differentially attribute such extreme weight-control behavior to altered reward responding and exaggerated cognitive control. In a novel test of these theoretical accounts, we employed an established cognitive effort discounting paradigm in combination with fMRI in young acutely underweight female patients with AN (n = 48) and age-matched healthy controls (HC; n = 48). Contrary to the hypothesis that individuals with AN would experience cognitive effort (operationalized as N-back task performance) as less costly than HC participants, groups did not differ in the subjective value (SV) of discounted rewards or in SV-related activation of brain regions involved in reward valuation. Rather, all group differences in both behavior (superior N-back performance in AN and associated effort ratings) and fMRI activation (increased SV-related frontoparietal activation during decision-making in AN even for easier choices) were more indicative of increased control. These findings suggest that while effort discounting may be relatively intact in AN, effort investment is high both when performing demanding tasks and during effort-based decision-making; highlighting cognitive overcontrol as an important therapeutic target. Future research should establish whether exaggerated control during effort-based decision-making persists after weight-recovery and explore learning the value of effort in AN with tasks involving disorder-relevant effort demands and rewards.

Food choice and neural reward systems in adolescents with anorexia nervosa and atypical anorexia nervosa

BACKGROUND

Adolescence is a critical developmental period for the study of anorexia nervosa (AN), an illness characterized by extreme restriction of food intake. The maturation of the reward system during adolescence combined with recent neurobiological models of AN led to the hypothesis that early on in illness, restrictive food choices would be associated with activity in nucleus accumbens reward regions, rather than caudate regions identified among adults with AN.

METHODS

Healthy adolescents (HC, n = 41) and adolescents with AN or atypical AN (atypAN, n = 76) completed a Food Choice Task during fMRI scanning. Selection of high-fat foods and choice-related activation in nucleus accumbens and anterior caudate regions-of-interest (ROIs) were compared between individuals with AN/atypAN and HC. Associations were examined between choice-related activation and choice preferences among the AN group. Exploratory analyses examined associations between choice-related activation and psychological assessments among the patient group.

RESULTS

Adolescents with AN or atypAN selected fewer high-fat foods than HC (t = -5.92, p < .001). Counter to predictions, there were no significant group differences in choice-related activation in the ROIs. Among individuals with AN or atypAN, choice-related neural activity in the anterior caudate was significantly negatively associated with high-fat food selections in the task (r = -.32, p = .024). In exploratory analyses, choice-related anterior caudate activation was positively associated with psychological measures of illness severity among patients (p's < .05, uncorrected).

CONCLUSIONS

In this large cohort of adolescents with AN/atypAN, there was no evidence of altered reward system engagement during food choice. While there was no group difference in choice-related caudate activation, the associations with choices and psychological measures continue to suggest that this neural region is implicated in illness. Longitudinal analyses will clarify whether neural variability relates to longer-term course.

Shortening duration of untreated illness in young people with first episode eating disorders: protocol of a randomised controlled feasibility trial of a smartphone friendly multi-modal decision-making tool (FREED-M) to improve help-seeking

BACKGROUND

Early intervention gives young people the best chance to recover from eating disorders (EDs). An important focus of early intervention is shortening the time between a person first developing symptoms and starting treatment (duration of untreated eating disorder; DUED). Patient-related factors (e.g. poor mental health literacy and help-seeking difficulties) are strongly associated with DUED. The aims of our study are to co-design and test the feasibility of FREED-Mobile (FREED-M), an online intervention tool for young people with early-stage EDs. This tool aims to improve knowledge about EDs, increase motivation to seek treatment and teach early steps towards change or recovery, thus reducing DUED.

METHODS

We will carry out a randomised controlled feasibility trial comparing the FREED-M tool with a control intervention where individuals are sign-posted to an ED charity website. The objectives of the proposed trial are to establish/estimate: (a) attrition rates at follow-up (primary feasibility outcome); (b) participant recruitment; (c) intervention uptake, completion rates and acceptability; (d) intervention effect sizes and standard deviations for outcomes to inform the sample size calculation for a large-scale randomised controlled trial (RCT); (e) stakeholder views on the intervention. We aim to recruit 116 participants (young people, aged 16-25, with first episode ED) from primary care, schools and universities, ED services and social media. Online assessments will be carried out at baseline, end of intervention and follow-up (weeks 0, 4 and 12 post-randomisation, respectively). Outcomes will include motivation and readiness to change, attitudes and intentions towards help-seeking, ED symptoms, mood and social functioning, and health-related quality of life. Additionally, we will carry out a qualitative evaluation of participants' views of the intervention and study design.

DISCUSSION

The results of this feasibility trial will inform adaptations to the intervention as needed, as well as the study design (e.g. sample size, primary outcomes) of a future large-scale RCT to assess the effectiveness of the FREED-M intervention. If effective, this novel, online intervention has the potential for wide dissemination and for substantially reducing DUED to improve long-term patient outcomes.

TRIAL REGISTRATION

ISRCTN, ISRCTN15662055. Registered 27 July 2022, https://www.isrctn.com/ISRCTN15662055 .

Reinforcement learning in women remitted from anorexia nervosa: Preliminary examination with a hybrid reinforcement learning/drift diffusion model

OBJECTIVE

Altered reinforcement learning (RL) and decision-making have been implicated in the pathophysiology of anorexia nervosa. To determine whether deficits observed in symptomatic anorexia nervosa are also present in remission, we investigated RL in women remitted from anorexia nervosa (rAN).

METHODS

Participants performed a probabilistic associative learning task that involved learning from rewarding or punishing outcomes across consecutive sets of stimuli to examine generalization of learning to new stimuli over extended task exposure. We fit a hybrid RL and drift diffusion model of associative learning to model learning and decision-making processes in 24 rAN and 20 female community controls (cCN).

RESULTS

rAN showed better learning from negative outcomes than cCN and this was greater over extended task exposure (p < .001, ηp2 = .30). rAN demonstrated a reduction in accuracy of optimal choices (p = .007, ηp2 = .16) and rate of information extraction on reward trials from set 1 to set 2 (p = .012, ηp2 = .14), and a larger reduction of response threshold separation from set 1 to set 2 than cCN (p = .036, ηp2 = .10).

CONCLUSIONS

rAN extracted less information from rewarding stimuli and their learning became increasingly sensitive to negative outcomes over learning trials. This suggests rAN shifted attention to learning from negative feedback while slowing down extraction of information from rewarding stimuli. Better learning from negative over positive feedback in rAN might reflect a marker of recovery.

Efficacy of transcranial magnetic stimulation in anorexia nervosa: a systematic review and meta-analysis

PURPOSE

Transcranial magnetic stimulation (TMS) has emerged as a promising treatment for various neuropsychiatric conditions, including depression, obsessive-compulsive disorder, and Parkinson's disease. Recent research has focused on evaluating its effectiveness in treating patients with anorexia nervosa (AN). This systematic review and meta-analysis examined the impact of TMS on patients with AN and evaluated any potential adverse effects.

METHODS

We conducted search according to PRISMA guidelines and comprehensively analyzed data from multiple databases, including Pubmed, Scopus, Embase, Web of Science, and the Cochrane Library, up to September 13th. Statistical analysis utilized the Comprehensive Meta-analysis software version 3.0.

RESULTS

The systematic review encompassed 17 studies, with nine undergoing meta-analyses. The primary target for TMS was the dorsolateral prefrontal cortex, with two studies targeting the dorsomedial prefrontal cortex, one targeting the insula and one targeting the inferior parietal lobe. The findings revealed a significant increase in body mass index (BMI) following TMS (SMD: -0.025, 95% CI: -0.0505 to -0.005, P-value = 0.045). Additionally, the Eating Disorder Examination Questionnaire (EDE-Q) score was quantitatively reported in six studies, which permitted its inclusion in the meta-analysis. The analysis exhibited a significant decrease in EDE-Q score after TMS (SMD: 0.634, 95% CI: 0.349-0.919, P-value < 0.001). Subgroup analysis based on TMS session duration indicated that the effect size of TMS on EDE-Q score is more pronounced when the session duration exceeds 20 min.

CONCLUSION

TMS represents an effective therapy for patients with AN, leading to improvements in both BMI and core symptoms of AN, with minor and transient side effects.

LEVEL OF EVIDENCE

Level I, systematic reviews and meta-analyses.

Considering Sufficient Weight Loss as a Prerequisite for Development of Anorexia Nervosa and Atypical Anorexia Nervosa

BACKGROUND

Because premorbid BMI strongly predicts the amount of weight loss in anorexia nervosa (AN)/atypical AN, we hypothesize that weight loss triggers both disorders by inducing the endocrine adaptation to starvation.

METHOD

We propose research to capture the onset of AN/atypical AN following intentional, otherwise behaviorally motivated, or unintentional weight loss in relationship to premorbid weight.

RESULTS

We propose retrospective and prospective studies to examine the temporal development of symptoms in AN/atypical AN. Given a greater frequency of weight loss behaviors in individuals with high BMIs, patients with intentionally driven weight loss should demonstrate a higher mean weight loss and greater premorbid weight and shape concerns. Practice guidelines necessitate weight gain for AN recovery, yet how weight gain induces improvements is unspecified and warrants systematic elucidation. Finally, we highlight implications for the current conceptualization of genetic and environmental contributors of AN/atypical AN in twin and molecular genetic studies.

CONCLUSION

We propose separating the starvation-induced mechanisms relevant for AN/atypical AN development from the reasons/mechanisms inherent to weight loss.

Revealing motor insensitivity to food in Anorexia Nervosa as a potential mechanism contributing to calorie restriction: A mobile Approach Avoidance Task study

A change in implicit behavioural tendencies toward foods may contribute to the maintenance of calorie restriction in Anorexia Nervosa (AN). To test this hypothesis, we assessed approach-avoidance tendencies toward different categories of stimuli using a novel mobile version of the approach-avoidance task (AAT). The sample included 66 patients with restrictive AN and 84 healthy controls, all females. All participants performed the AAT in which they were required to approach or avoid stimuli (high-calorie foods, low-calorie foods, and neutral objects) by respectively pulling their phone towards themselves of pushing it away. Both the response time and the force of each movement were collected by means of the smartphone's accelerometer. The results revealed that patients with AN had a reduced tendency to approach food stimuli compared to healthy controls, who instead presented faster and stronger movements in approaching rather than avoiding foods as compared to neutral objects. This finding was particularly pronounced in patients with greater levels of malnutrition. No differences were instead observed comparing high-calorie and low-calorie foods. The observed reduction in the natural tendency to approach food stimuli is consistent with patients' eating behaviour and may contribute to the maintenance of calorie restriction, thus representing a possible target for novel therapeutic approaches.

Altered value-based decision-making in anorexia nervosa: A systematic review

Alterations in decision-making are considered core to anorexia nervosa (AN) phenomenology and may maintain illness through maladaptive choice behavior. This systematic review (n = 77) aimed to extend prior reviews beyond standard neuropsychological batteries by incorporating novel value-based choice tasks and computational methods. We organize findings across key factors, including: 1) illness state, 2) developmental stage, and 3) AN subtype, and highlight available neuroimaging findings. Differences in decision-making appear consistent during illness, including in weight-restored samples, but not in recovery and not in all domains. Differences are not consistently present in adolescence, although punishment sensitivity may be heightened; AN subtypes are not consistently distinguishable. Overall, decision-making varies by context and is influenced by reward/punishment processing, risk/uncertainty, and flexibility/control. Utilization of computational modeling methods, possibly increasing precision, highlight that, although raw behavior may not differ at recovery, latent decision-making processes appear impacted. Clinical interventions may benefit from consideration of context when working to shape choice behavior and from consideration of latent decision-making processes that influence how choices are made.

Repeated stress triggers seeking of a starvation-like state in anxiety-prone female mice

Elevated anxiety often precedes anorexia nervosa and persists after weight restoration. Patients with anorexia nervosa often describe self-starvation as pleasant, potentially because food restriction can be anxiolytic. Here, we tested whether repeated stress can cause animals to prefer a starvation-like state. We developed a virtual reality place preference paradigm in which head-fixed mice can voluntarily seek a starvation-like state induced by optogenetic stimulation of hypothalamic agouti-related peptide (AgRP) neurons. Prior to stress exposure, males but not females showed a mild aversion to AgRP stimulation. Strikingly, following multiple days of stress, a subset of females developed a strong preference for AgRP stimulation that was predicted by high baseline anxiety. Such stress-induced changes in preference were reflected in changes in facial expressions during AgRP stimulation. Our study suggests that stress may cause females predisposed to anxiety to seek a starvation state and provides a powerful experimental framework for investigating the underlying neural mechanisms.

A multi-modal assessment of fear conditioning in adolescent anorexia nervosa

OBJECTIVE

Anorexia nervosa (AN) is a pernicious psychiatric disorder which is principally characterized by a fear of weight gain. Notwithstanding the centrality of fear in the psychopathology of AN, controlled assessments of negative valence systems are lacking. Herein we assess fear conditioning in adolescent females with AN.

METHOD

Adolescent girls (Mage = 14.6 years, ±1.57) with DSM-5 diagnoses of AN (N = 25) and age-matched control girls (Mage = 14.8 years, ±1.46) with no DSM-5 diagnoses (N = 25) completed structured clinical interviews and participated in a classical three-phase Pavlovian fear conditioning paradigm. Participants with comorbid anxiety disorders were excluded. Skin conductance response (SCR) was measured, alongside self-reported fear, valence, and fear expectancy ratings.

RESULTS

Both groups demonstrated significant differential acquisition across all four measures. Regarding group comparisons, no differences emerged for self-reported fear, valence, and fear expectancy ratings during acquisition, although for SCR, those with AN demonstrated reduced physiological arousal relative to controls. Both groups demonstrated significant differential extinction for unconditioned stimuli (US) expectancy, self-report fear, and self-report valence. No statistically significant group differences were evident during extinction to the conditioned stimuli (CS)+, on any outcome measure. However, controls reported more positive valence to the CS- than those with AN.

CONCLUSIONS

Contrary to our hypotheses, our preliminary assessment did not find support for elevated fear responding among adolescent girls with AN with regards to fear acquisition or extinction. These data suggest that AN in adolescent girls may not be associated with a heightened propensity to acquire fear, but conversely, may suggest that exposure treatments for AN may be helpful, since extinction learning is intact in AN.

PUBLIC SIGNIFICANCE

AN is characterized by fear-related symptoms, including food and weight-related fear, and behavioral avoidance, yet controlled studies assessing fear learning are limited. Our preliminary assessment of adolescent AN indicates no abnormalities in fear learning among adolescents with AN. These findings may inform existing mechanistic models of AN psychopathology, and the development of exposure-based treatments for AN.

Dynamic Amygdala Nuclei Alterations in Relation to Weight Status in Anorexia Nervosa Are Mediated by Leptin

OBJECTIVE

The amygdaloid complex is a subcortical limbic group of distinct nuclei. In a previous patient-control study, differential amygdala nuclei alterations were found in acute anorexia nervosa (AN); rostral-medial nuclei involved in fear and reward processing were substantially reduced in volume and associated with hypoleptinemia, a key neuroendocrine characteristic of AN. Here, longitudinal amygdala nuclei alterations in AN were investigated in relation to weight status and their associations with leptin levels.

METHOD

T1-weighted structural magnetic resonance imaging scans were longitudinally processed with FreeSurfer. Amygdala nuclei volumes in young female patients with acute AN before and after short-term weight restoration (n = 110, >14% body mass index increase over 3 months) and female participants with a history of AN (n = 79, long-term [mean 5 years] weight recovered) were compared with female healthy control participants (n = 271) using linear mixed effects models.

RESULTS

Rostral-medially clustered amygdala nuclei volumes, accessory basal, cortical, medial nuclei, and corticoamygdaloid transition, increased during short-term weight restoration (Cohen's d range 0.18-0.30). However, volumetric normalization across nuclei was heterogeneous. Right cortical, medial nuclei, bilateral corticoamygdaloid transitions, and anterior amygdaloid areas were only partially normalized following short-term weight restoration. Right anterior amygdaloid area remained reduced after long-term weight recovery compared with control participants (d = 0.36). Leptin increase, accompanying short-term weight restoration, mediated the effect of weight gain on volumetric increase in left corticoamygdaloid transition and bilateral medial nuclei.

CONCLUSION

Rostral-medially clustered amygdala nuclei show pronounced volumetric increase but incomplete normalization in AN during and after short-term weight restoration. Leptin increase may be relevant for the recovery of specific amygdala nuclei in addition to nutritional rehabilitation, indicating links between amygdala substructure and leptin dynamics of potential pathophysiological and clinical relevance in AN.

PLAIN LANGUAGE SUMMARY

The amygdala plays a critical role in processing fearful and rewarding stimuli, and alterations in the amygdala are associated with anorexia nervosa. In this study, the authors measured amygdala nuclei volumes in female patients with acute anorexia nervosa undergoing weight-restoration treatment (n = 110), long-term weight-recovered individuals with anorexia (n = 79), and healthy control participants (n = 271). Structural magnetic resonance imaging revealed that volumes of specific nuclei, clustered in the rostral-medial amygdala, were substantially reduced in acute anorexia nervosa and only partially normalized following weight restoration treatment. Residual reductions in volume persisted even after long-term weight-recovery, compared to healthy control participants. Short-term weight restoration was associated with increases in the neurohormone leptin, and increasing leptin levels were found to mediate the positive impact of weight gain on increased amygdala volume over the treatment course.

DIVERSITY & INCLUSION STATEMENT

We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. We worked to ensure that the study questionnaires were prepared in an inclusive way. One or more of the authors of this paper received support from a program designed to increase minority representation in science. We actively worked to promote sex and gender balance in our author group. We actively worked to promote inclusion of historically underrepresented racial and/or ethnic groups in science in our author group. While citing references scientifically relevant for this work, we also actively worked to promote sex and gender balance in our reference list. While citing references scientifically relevant for this work, we also actively worked to promote inclusion of historically underrepresented racial and/or ethnic groups in science in our reference list. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.

[Effects of non-invasive neuromodulation on the cognitive profile of people with anorexia nervosa: A scoping review]

BACKGROUND

The use of non-invasive neuromodulation is emerging in the treatment of anorexia nervosa. Despite promising results, further research is needed to improve our understanding of these techniques and to adapt interventions to this population. As anorexia nervosa is associated with several cognitive difficulties and cerebral anomalies, the aim of the present study was to summarize the available data on the effects of non-invasive neuromodulation on the neuropsychological profile of people with anorexia nervosa.

METHOD

A scoping review was conducted by searching in PsycINFO, PubMed and CINAHL databases to systematically identify relevant studies published between 1994 and 2023 on the treatment of anorexia nervosa with repetitive transcranial magnetic stimulation, transcranial direct current stimulation or neurofeedback electroencephalogram.

RESULTS

Seventeen articles were included, including 12 on repetitive transcranial magnetic stimulation, four on transcranial direct current stimulation and one on neurofeedback electroencephalogram. Of these, only three studies included a neuropsychological measure to assess the impact of neuromodulation on participants' cognitive functions.

CONCLUSIONS

Including detailed neuropsychological measures in clinical trials of non-invasive neuromodulation is highly recommended and appears essential to improve our understanding of these techniques and optimize their efficacy in the treatment of anorexia nervosa.

A randomised controlled feasibility trial of intermittent theta burst stimulation with an open longer-term follow-up for young people with persistent anorexia nervosa (RaISE): Study protocol

OBJECTIVE

We present the protocol of a feasibility randomised controlled trial (RCT) of intermittent theta burst stimulation (iTBS) for young people with anorexia nervosa (AN). Effective first-line psychological therapies exist for young people with AN, but little is known about how to treat those who do not respond. Non-invasive neuromodulation, such as iTBS, could address unmet treatment needs by targeting neurocircuitry associated with the development and/or maintenance of AN.

DESIGN

Sixty-six young people (aged 13-30 years) with persistent AN will be randomly allocated to receive 20 sessions of real or sham iTBS over the left dorsolateral prefrontal cortex in addition to their usual treatment. Outcomes will be measured at baseline, post-treatment (1-month post-randomisation) and 4-months post-randomisation (when unblinding will occur). Additional open follow-ups will be conducted at 12- and 24-months post-randomisation. The primary feasibility outcome is the proportion of participants retained in the study at 4-months. Secondary outcomes include AN symptomatology, other psychopathology, quality of life, service utilisation, neurocognitive processes, and neuroimaging measures.

DISCUSSION

Findings will inform the development of a future large-scale RCT. They will also provide exploratory data on treatment efficacy, and neural and neurocognitive predictors and correlates of treatment response to iTBS in AN.

Development of activity-based anorexia requires PKC-δ neurons in two central extended amygdala nuclei

Anorexia nervosa (AN) is a serious psychiatric disease, but the neural mechanisms underlying its development are unclear. A subpopulation of amygdala neurons, marked by expression of protein kinase C-delta (PKC-δ), has previously been shown to regulate diverse anorexigenic signals. Here, we demonstrate that these neurons regulate development of activity-based anorexia (ABA), a common animal model for AN. PKC-δ neurons are located in two nuclei of the central extended amygdala (EAc): the central nucleus (CeA) and oval region of the bed nucleus of the stria terminalis (ovBNST). Simultaneous ablation of CeAPKC-δ and ovBNSTPKC-δ neurons prevents ABA, but ablating PKC-δ neurons in the CeA or ovBNST alone is not sufficient. Correspondingly, PKC-δ neurons in both nuclei show increased activity with ABA development. Our study shows how neurons in the amygdala regulate ABA by impacting both feeding and wheel activity behaviors and support a complex heterogeneous etiology of AN.

Temperament impact on eating disorder symptoms and habit formation: a novel model to inform treatment

BACKGROUND

Temperament has long been described as the biological dimension of personality. Due to advancing brain-imaging technology, our understanding of temperament has deepened and transformed over the last 25 years. Temperament combines genetic, neurobiological and trait research. Temperament has been included peripherally in some eating disorder (ED) treatment approaches but has been ignored by most. Temperament fills a fundamental treatment gap by clarifying who is more vulnerable to develop ED and why some individuals are susceptible to specific ED symptoms while others are not. In addition, temperament targets possible treatment solutions.

MAIN TEXT

There is a need for a novel model that incorporates and explores the role of temperament in ED treatment intervention. This paper is a metaphoric temperament model to inform treatment intervention. It describes how temperament traits influences new decisions which impact new behavioural responses. In turn, it neurobiologically tracks how and why the brain efficiently transforms new decisions into new habits. This model integrates both temperament and habit research to explore (a) what temperament is; (b) how new decisions develop into habits neurobiologically; (c) that the brain wires destructive symptoms into habits in the same way that it wires healthy/productive behaviours into habits; (d) traits that trigger ED symptoms are the same traits that influence productive behaviours; and in regard to treatment implications (e) when treatment structure and intervention target client temperaments, the potential for new healthy "trait-syntonic" habits could develop.

CONCLUSIONS

This paper introduces a metaphoric model that synthesizes and integrates temperament neurobiological and trait findings with ED symptoms, habits, and client trait-based solutions. The model synthesizes and integrates different research domains to establish a brain-based foundation to inform treatment intervention. The model targets clients' temperament traits as central collections of innate self-expressions that could be utilized as tools to redirect client trait-syntonic ED responses into trait-syntonic productive outcomes. The brain bases of temperament and habit formation serve as a biological foundation for ED treatment intervention.

Change in motivational bias during treatment predicts outcome in anorexia nervosa

OBJECTIVE

Reward and punishment sensitivity are known to be altered in anorexia nervosa (AN). Most research has examined these constructs separately although motivated behavior is influenced by considering both the potential for reward and risk of punishment. The present study sought to compare the relative balance of reward and punishment sensitivity in AN versus healthy controls (HCs) and examine whether motivational bias is associated with AN symptoms and treatment outcomes.

METHODS

Adolescents and adults with AN (n = 262) in a partial hospitalization program completed the Eating Disorders Examination Questionnaire (EDE-Q), Behavioral Inhibition System/Behavioral Activation System (BIS/BAS) scales, and Sensitivity to Punishment/Sensitivity to Reward Questionnaire (SPSRQ) at admission and discharge. HCs (HC; n = 90) completed the BIS/BAS and SPSRQ. Motivational Bias Scores were calculated to reflect the dominance of reward versus punishment sensitivity.

RESULTS

Individuals with AN demonstrated significantly greater bias toward punishment sensitivity than HC. In AN, a bias toward punishment was associated with higher EDE-Q Global score at admission. Change in motivational bias during treatment predicted EDE-Q Global scores, but not BMI, at discharge, with greater increases in reward sensitivity or greater decreases in punishment sensitivity during treatment predicting lower eating pathology. Similar findings were observed using the BIS/BAS and SPSRQ.

DISCUSSION

Change in motivational bias during treatment is associated with improved outcomes in AN. However, it appears that much of the change in motivational bias can be attributed to changes in punishment sensitivity, rather than reward sensitivity. Future research should examine the mechanisms underlying punishment sensitivity decreases during treatment.

PUBLIC SIGNIFICANCE

Sensitivity to reward and punishment may be important treatment targets for individuals with anorexia nervosa (AN). To date, most research has considered reward and punishment sensitivity separately, rather than examining their relationship to each other. We found that the balance of reward and punishment sensitivity (i.e., motivational bias) differs between healthy controls and those with AN and that this bias is associated with eating disorder symptoms and treatment outcome.

Greater reliance on model-free learning in adolescent anorexia nervosa: An examination of dual-system reinforcement learning

Alterations in learning and decision-making systems are thought to contribute to core features of anorexia nervosa (AN), a psychiatric disorder characterized by persistent dietary restriction and weight loss. Instrumental learning theory identifies a dual-system of habit and goal-directed decision-making, linked to model-free and model-based reinforcement learning algorithms. Difficulty arbitrating between these systems, resulting in an over-reliance on one strategy over the other, has been implicated in compulsivity and extreme goal pursuit, both of which are observed in AN. Characterizing alterations in model-free and model-based systems, and their neural correlates, in AN may clarify mechanisms contributing to symptom heterogeneity (e.g., binge/purge symptoms). This study tested whether adolescents with restricting AN (AN-R; n = 36) and binge/purge AN (AN-BP; n = 20) differentially utilized model-based and model-free learning systems compared to a healthy control group (HC; n = 28) during a Markov two-step decision-making task under conditions of reward and punishment. Associations between model-free and model-based learning and resting-state functional connectivity between neural regions of interest, including orbitofrontal cortex (OFC), nucleus accumbens (NAcc), putamen, and sensory motor cortex (SMC) were examined. AN-R showed higher utilization of model-free learning compared to HC for reward, but attenuated model-free and model-based learning for punishment. In AN-R only, higher model-based learning was associated with stronger OFC-to-left NAcc functional connectivity, regions linked to goal-directed behavior. Greater utilization of model-free learning for reward in AN-R may differentiate this group, particularly during adolescence, and facilitate dietary restriction by prioritizing habitual control in rewarding contexts.

The cerebellum plays more than one role in the dysregulation of appetite: Review of structural evidence from typical and eating disorder populations

OBJECTIVE

Dysregulated appetite control is characteristic of anorexia nervosa (AN), bulimia nervosa (BN), and obesity (OB). Studies using a broad range of methods suggest the cerebellum plays an important role in aspects of weight and appetite control, and is implicated in both AN and OB by reports of aberrant gray matter volume (GMV) compared to nonclinical populations. As functions of the cerebellum are anatomically segregated, specific localization of aberrant anatomy may indicate the mechanisms of its relationship with weight and appetite in different states. We sought to determine if there were consistencies in regions of cerebellar GMV changes in AN/BN and OB, as well as across normative (NOR) variation.

METHOD

Systematic review and meta-analysis using GingerALE.

RESULTS

Twenty-six publications were identified as either case-control studies (nOB  = 277; nAN/BN  = 510) or regressed weight from NOR data against brain volume (total n = 3830). AN/BN and OB analyses both showed consistently decreased GMV within Crus I and Lobule VI, but volume reduction was bilateral for AN/BN and unilateral for OB. Analysis of the NOR data set identified a cluster in right posterior lobe that overlapped with AN/BN cerebellar reduction. Sensitivity analyses indicated robust repeatability for NOR and AN/BN cohorts, but found OB-specific heterogeneity.

DISCUSSION

Findings suggest that more than one area of the cerebellum is involved in control of eating behavior and may be differentially affected in normal variation and pathological conditions. Specifically, we hypothesize an association with sensorimotor and emotional learning via Lobule VI in AN/BN, and executive function via Crus I in OB.

Severe-Enduring Anorexia Nervosa (SE-AN): a case series

BACKGROUND

Anorexia Nervosa (AN) poses significant therapeutic challenges, especially in cases meeting the criteria for Severe and Enduring Anorexia Nervosa (SE-AN). This subset of AN is associated with severe medical complications, frequent use of services, and the highest mortality rate among psychiatric disorders.

CASE PRESENTATION

In the present case series, 14 patients were selected from those currently or previously taken care of at the Eating Disorders Outpatients Unit of the Maggiore Hospital in Bologna between January 2012 and May 2023. This case series focuses on the effects of the disease, the treatment compliance, and the description of those variables that could help understand the great complexity of the disorder.

CONCLUSION

This case series highlights the relevant issue of resistance to treatment, as well as medical and psychological complications that mark the life course of SE-AN patients. The chronicity of these disorders is determined by the overlapping of the disorder's ego-syntonic nature, the health system's difficulty in recognizing the problem in its early stages, and the presence of occupational and social impairment.

Exploring the thalamus: a crucial hub for brain function and communication in patients with bulimia nervosa

BACKGROUND

Bulimia nervosa (BN) is an eating disorder characterized by recurrent binge eating and compensatory behaviors. The thalamus plays a crucial role in the neural circuitry related to eating behavior and needs to be further explored in BN.

METHODS

In this study, 49 BN patients and 44 healthy controls (HCs) were recruited. We applied the fractional amplitude of low-frequency fluctuation to investigate regional brain activity in the thalamus and functional connectivity (FC) to examine the synchronization of activity between thalamic subregions and other brain regions in both groups. All results underwent false discovery rate (p < 0.05, FDR correction) correction. Pearson correlation analysis was performed to assess the relationship between the patients' abnormal clinical performance and the thalamic alterations (p < 0.05, FDR correction).

RESULTS

We found no significant differences in neural activity between BN patients and HCs in the sixteen thalamic subregions. However, compared to the HCs, the individuals with BN showed decreased FC between the thalamic subregions and several regions, including the bilateral prefrontal cortex, right inferior parietal lobule, right supplementary motor area, right insula, cingulate gyrus and vermis. Additionally, BN patients showed increased FC between the thalamic subregions and visual association regions, primary sensorimotor cortex, and left cerebellum. These altered FC patterns in the thalamus were found to be correlated with clinical variables (the frequency of binge eating/purging per week and external eating behavior scale scores) in the BN group. All results have passed FDR correction.

CONCLUSIONS

Our study provides evidence that there is disrupted FC between thalamic subregions and other brain regions in BN patients during resting state. These regions are primarily located within the frontoparietal network, default mode network, somatosensory, and visual network. These findings elucidate the neural activity characteristics underlying BN and suggest that thalamic subregions have potential as targets for future neuromodulation interventions.

Strategic avoidance of food stimuli in patients with restrictive anorexia nervosa: An eye-tracking evaluation

OBJECTIVE

A biased attentional processing of food stimuli may represent a disorder maintenance factor in patients with anorexia nervosa (AN). The present study aimed at investigating the temporal course of attentional deployment towards both high-calorie and low-calorie foods in patients with AN using eye-tracking.

METHOD

Fifty-two patients with restrictive AN and 54 healthy controls (HC) performed a dot-probe task while their gaze was recorded with an eye-tracking system. The direction bias (percentage of trials in which the gaze was directed towards the food at first fixation, 500, and 1500 ms), and the duration bias (percentage of time spent looking at the food) were extracted.

RESULTS

Regarding the direction bias, a group by time interaction emerged (F = 3.29, p = 0.038): while in the control group the bias continued to increase over the course of the trial, patients with AN showed a reduction of the bias between the 500 and 1500 ms. No group differences were observed on the duration bias.

CONCLUSIONS

In advanced stages of attentional deployment patients with AN start to differ from HC by diverting their attention away from food stimuli, a strategic process that may contribute to food avoidance and calorie restriction.

Habits and Persistent Food Restriction in Patients with Anorexia Nervosa: A Scoping Review

The aetiology of anorexia nervosa (AN) presents a puzzle for researchers. Recent research has sought to understand the behavioural and neural mechanisms of these patients' persistent choice of calorie restriction. This scoping review aims to map the literature on the contribution of habit-based learning to food restriction in AN. PRISMA-ScR guidelines were adopted. The search strategy was applied to seven databases and to grey literature. A total of 35 studies were included in this review. The results indicate that the habit-based learning model has gained substantial attention in current research, employing neuroimaging methods, scales, and behavioural techniques. Food choices were strongly associated with dorsal striatum activity, and habitual food restriction based on the self-report restriction index was associated with clinical impairment in people chronically ill with restricting AN. High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) and Regulating Emotions and Changing Habits (REaCH) have emerged as potential treatments. Future research should employ longitudinal studies to investigate the time required for habit-based learning and analyse how developmental status, such as adolescence, influences the role of habits in the progression and severity of diet-related illnesses. Ultimately, seeking effective strategies to modify persistent dietary restrictions controlled by habits remains essential.

Differential alterations of amygdala nuclei volumes in acutely ill patients with anorexia nervosa and their associations with leptin levels

BACKGROUND

The amygdala is a subcortical limbic structure consisting of histologically and functionally distinct subregions. New automated structural magnetic resonance imaging (MRI) segmentation tools facilitate the in vivo study of individual amygdala nuclei in clinical populations such as patients with anorexia nervosa (AN) who show symptoms indicative of limbic dysregulation. This study is the first to investigate amygdala nuclei volumes in AN, their relationships with leptin, a key indicator of AN-related neuroendocrine alterations, and further clinical measures.

METHODS

T1-weighted MRI scans were subsegmented and multi-stage quality controlled using FreeSurfer. Left/right hemispheric amygdala nuclei volumes were cross-sectionally compared between females with AN (n = 168, 12-29 years) and age-matched healthy females (n = 168) applying general linear models. Associations with plasma leptin, body mass index (BMI), illness duration, and psychiatric symptoms were analyzed via robust linear regression.

RESULTS

Globally, most amygdala nuclei volumes in both hemispheres were reduced in AN v. healthy control participants. Importantly, four specific nuclei (accessory basal, cortical, medial nuclei, corticoamygdaloid transition in the rostral-medial amygdala) showed greater volumetric reduction even relative to reductions of whole amygdala and total subcortical gray matter volumes, whereas basal, lateral, and paralaminar nuclei were less reduced. All rostral-medially clustered nuclei were positively associated with leptin in AN independent of BMI. Amygdala nuclei volumes were not associated with illness duration or psychiatric symptom severity in AN.

CONCLUSIONS

In AN, amygdala nuclei are altered to different degrees. Severe volume loss in rostral-medially clustered nuclei, collectively involved in olfactory/food-related reward processing, may represent a structural correlate of AN-related symptoms. Hypoleptinemia might be linked to rostral-medial amygdala alterations.

Psychedelics in the treatment of eating disorders: Rationale and potential mechanisms

Eating disorders are serious illnesses showing high rates of mortality and comorbidity with other mental health problems. Psychedelic-assisted therapy has recently shown potential in the treatment of several common comorbidities of eating disorders, including mood disorders, post-traumatic stress disorder, and substance use disorders. The theorized therapeutic mechanisms of psychedelic-assisted therapy suggest that it could be beneficial in the treatment of eating disorders as well. In this review, we summarize preliminary data on the efficacy of psychedelic-assisted therapy in people with anorexia nervosa, bulimia nervosa, and binge eating disorder, which include studies and case reports of psychedelic-assisted therapy with ketamine, MDMA, psilocybin, and ayahuasca. We then discuss the potential therapeutic mechanisms of psychedelic-assisted therapy in these three eating disorders, including both general therapeutic mechanisms and those which are relatively specific to eating disorders. We find preliminary evidence that psychedelic-assisted therapy may be effective in the treatment of anorexia nervosa and bulimia nervosa, with very little data available on binge eating disorder. Regarding mechanisms, psychedelic-assisted therapy may be able to improve beliefs about body image, normalize reward processing, promote cognitive flexibility, and facilitate trauma processing. Just as importantly, it appears to promote general therapeutic factors relevant to both eating disorders and many of their common comorbidities. Lastly, we discuss potential safety concerns which may be associated with these treatments and present recommendations for future research.

Excitatory and inhibitory neurometabolites in anorexia nervosa: A systematic review of proton magnetic resonance spectroscopy studies

The dysregulation of excitatory and inhibitory neurotransmission is considered a pathological marker of Anorexia Nervosa (AN), however, no systematic evaluation of the proton Magnetic Resonance Spectroscopy (1H-MRS) literature has been conducted to date. Accordingly, we conducted a systematic review of neurometabolite differences between individuals with AN and healthy controls (HC). A comprehensive database search (until June 2023) identified seven studies meeting inclusion criteria. Samples included adolescents and adults with similar mean age (AN: 22.20 HC: 22.60), and female percentages (AN: 98%; HC: 94%). The review found a considerable need for improving study design and the reporting of MRS sequence parameters and analysis. Reduced glutamate concentrations in the ACC and OCC, and reduced Glx concentrations in the ACC were reported by one and two studies, respectively. Lastly, only one study to date has quantified GABA concentrations, with no significant differences found. In conclusion, there is currently insufficient evidence of excitatory and inhibitory neurometabolites changes in AN. As the 1H-MRS literature in AN increases, the key questions herein proposed must be revisited.

Neural effects of deep brain stimulation on reward and loss anticipation and food viewing in anorexia nervosa: a pilot study

BACKGROUND

Anorexia nervosa (AN) is a severe and life-threatening psychiatric disorder. Initial studies on deep brain stimulation (DBS) in severe, treatment-refractory AN have shown clinical effects. However, the working mechanisms of DBS in AN remain largely unknown. Here, we used a task-based functional MRI approach to understand the pathophysiology of AN.

METHODS

We performed functional MRI on four AN patients that participated in a pilot study on the efficacy, safety, and functional effects of DBS targeted at the ventral limb of the capsula interna (vALIC). The patients and six gender-matched healthy controls (HC) were investigated at three different time points. We used an adapted version of the monetary incentive delay task to probe generic reward processing in patients and controls, and a food-specific task in patients only.

RESULTS

At baseline, no significant differences for reward anticipation were found between AN and HC. Significant group (AN and HC) by time (pre- and post-DBS) interactions were found in the right precuneus, right putamen, right ventral and medial orbitofrontal cortex (mOFC). No significant interactions were found in the food viewing task, neither between the conditions high-calorie and low-calorie food images nor between the different time points. This could possibly be due to the small sample size and the lack of a control group.

CONCLUSION

The results showed a difference in the response of reward-related brain areas post-DBS. This supports the hypotheses that the reward circuitry is involved in the pathogenesis of AN and that DBS affects responsivity of reward-related brain areas. Trial registration Registered in the Netherlands Trial Register ( https://www.trialregister.nl/trial/3322 ): NL3322 (NTR3469).

Food induced distractibility in restrictive anorexia nervosa: Different motor patterns for different foods as revealed by a mouse tracker evaluation

An altered automatic processing of food stimuli may contribute to the maintenance of calorie restriction in patients with restrictive Anorexia Nervosa (AN-R). The present study aimed to assess whether task-irrelevant food distractors elicited a different interference effect in the motor actions of patients with AN-R compared to healthy controls (HC). 40 patients with acute AN-R and 40 HC performed an irrelevant distractor task in which they were required to perform a reaching movement from a starting point to a green dot, while an irrelevant distractor (a high-calorie food, low-calorie food, or neutral object) was presented in the middle of the screen. Mouse trajectories and response times (RT) were recorded. The analyses conducted on the kinematic variables revealed that while the trajectories of HC veered similarly toward the three categories of stimuli, AN-R patients showed an increased deviation toward low-calorie foods and a reduced deviation toward high-calorie foods compared to neutral objects. No significant results emerged as regards RT. The pattern of responses observed in patients with AN-R (deviation increased toward low-calorie and reduced toward high-calorie) is consistent with their eating habits and may thus represent an implicit mechanism sustaining calorie restriction in patients with AN-R.

The effects of acute tryptophan depletion on instrumental reward learning in anorexia nervosa - an fMRI study

BACKGROUND

The serotonin (5-HT) hypothesis of anorexia nervosa (AN) posits that individuals predisposed toward or recovered from AN (recAN) have a central nervous hyperserotonergic state and therefore restrict food intake as a means to reduce 5-HT availability (via diminished tryptophan-derived precursor supply) and alleviate associated negative mood states. Importantly, the 5-HT system has also been generally implicated in reward processing, which has also been shown to be altered in AN.

METHODS

In this double-blind crossover study, 22 individuals recAN and 25 healthy control participants (HC) underwent functional magnetic resonance imaging (fMRI) while performing an established instrumental reward learning paradigm during acute tryptophan depletion (ATD; a dietary intervention that lowers central nervous 5-HT availability) as well as a sham depletion.

RESULTS

On a behavioral level, the main effects of reward and ATD were evident, but no group differences were found. fMRI analyses revealed a group × ATD × reward level interaction in the ventral anterior insula during reward anticipation as well as in the medial orbitofrontal cortex during reward consumption.

DISCUSSION

The precise pattern of results is suggestive of a 'normalization' of reward-related neural responses during ATD in recAN compared to HC. Our results lend further evidence to the 5-HT hypothesis of AN. Decreasing central nervous 5-HT synthesis and availability during ATD and possibly also by dieting may be a means to normalize 5-HT availability and associated brain processes.

Chronic stress triggers seeking of a starvation-like state in anxiety-prone female mice

Elevated anxiety often precedes anorexia nervosa and persists after weight restoration. Patients with anorexia nervosa often describe hunger as pleasant, potentially because food restriction can be anxiolytic. Here, we tested whether chronic stress can cause animals to prefer a starvation-like state. We developed a virtual reality place preference paradigm in which head-fixed mice can voluntarily seek a starvation-like state induced by optogenetic stimulation of hypothalamic agouti-related peptide (AgRP) neurons. Prior to stress induction, male but not female mice showed mild aversion to AgRP stimulation. Strikingly, following chronic stress, a subset of females developed a strong preference for AgRP stimulation that was predicted by high baseline anxiety. Such stress-induced changes in preference were reflected in changes in facial expressions during AgRP stimulation. Our study suggests that stress may cause females predisposed to anxiety to seek a starvation state, and provides a powerful experimental framework for investigating the underlying neural mechanisms.

Emerging therapeutic targets for anorexia nervosa

INTRODUCTION

Anorexia nervosa is a frequent eating disorder that affects predominantly young women and may take a severe and chronically worsening course of disease contributing to its high mortality rate. Although a multitude of treatment options exist, this disease still bears a high relapse rate. In light of these facts, an improvement of existing and development of new treatment targets and options is warranted.

AREAS COVERED

The present review article covers recent developments in psychotherapy associated with the respective neuropsychological and brain alterations as well as highlights current and future pharmacotherapeutic options.

EXPERT OPINION

Several encouraging developments in the field of psychotherapy such as interventions targeting neurocognitive profiles or addressing reward processing, brain stimulation as well as pharmacological modulation of hormones, namely leptin, oxytocin, ghrelin and nesfatin-1 signaling might be - most likely as part of a multimodal treatment approach - efficacious in order to improve treatment of patients with anorexia nervosa, especially those with a severe course of disease as well as comorbidities. As anorexia nervosa represents a complex and severe mental disorder, it seems most likely that a combination and integration of different evidence-based treatment approaches and settings will contribute to an improved prognosis of this eating disorder. This should be further explored in future studies.

Novel ketamine and zinc treatment for anorexia nervosa and the potential beneficial interactions with the gut microbiome

Anorexia nervosa (AN) is a severe illness with diverse aetiological and maintaining contributors including neurobiological, metabolic, psychological, and social determining factors. In addition to nutritional recovery, multiple psychological and pharmacological therapies and brain-based stimulations have been explored; however, existing treatments have limited efficacy. This paper outlines a neurobiological model of glutamatergic and γ-aminobutyric acid (GABA)-ergic dysfunction, exacerbated by chronic gut microbiome dysbiosis and zinc depletion at a brain and gut level. The gut microbiome is established early in development, and early exposure to stress and adversity contribute to gut microbial disturbance in AN, early dysregulation to glutamatergic and GABAergic networks, interoceptive impairment, and inhibited caloric harvest from food (e.g., zinc malabsorption, competition for zinc ions between gut bacteria and host). Zinc is a key part of glutamatergic and GABAergic networks, and also affects leptin and gut microbial function; systems dysregulated in AN. Low doses of ketamine in conjunction with zinc, could provide an efficacious combination to act on NMDA receptors and normalise glutamatergic, GABAergic and gut function in AN.

The importance of including occupational therapists as part of the multidisciplinary team in the management of eating disorders: a narrative review incorporating lived experience

The literature demonstrates the importance of utilizing a multidisciplinary approach in the treatment of eating disorders, however there is limited literature identifying the optimal team of professionals for providing comprehensive and effective care. It is widely accepted that the multidisciplinary treatment team should include a physician, a mental health professional, and a dietitian, but there is minimal literature explaining what other professionals should be involved in the medical assessment and management of eating disorders. Additional team members might include a psychiatrist, therapist, social worker, activity therapist, or occupational therapist. Occupational therapists are healthcare professionals who help their clients participate in the daily activities, referred to as occupations, that they have to do, want to do, and enjoy doing. Many factors (e.g., medical, psychological, cognitive, physical) can impact a person's ability to actively engage in their occupations. When a person has an eating disorder, it is likely that all four of the aforementioned factors will be affected, thus individuals undergoing treatment for an eating disorder benefit from the incorporation of occupational therapy in supporting their recovery journey. This narrative review strives to provide education on the role of the occupational therapist in treating eating disorders and the need for increased inclusion of this profession on the multidisciplinary team. Additionally, this narrative review offers insight into an individual's personal experience with occupational therapy (i.e., lived experience) during her battle for eating disorder recovery and the unique value that occupational therapy offered her as she learned to manage her eating disorder. Research suggests that occupational therapy should be included in multidisciplinary teams focused on managing eating disorders as it empowers individuals to return to activities that bring personal meaning and identity.

The role of the brain-derived neurotrophic factor (BDNF) in anorexia nervosa

The brain-derived neurotrophic factor (BDNF) is a growth factor belonging to the neurotrophin family which plays a pivotal role in the differentiation, survival, and plasticity of neurons in the central nervous system. Evidence suggests that BDNF is an important signal molecule in the regulation of energy balance and thus implicated in body weight control. The discovery of BDNF-expressing neurons in the paraventricular hypothalamus which is important in the regulation of energy intake, physical activity, and thermogenesis gives more evidence to the suggested participation of BDNF in eating behavior. Until now it remains questionable whether BDNF can be used as a reliable biomarker for eating disorders such as anorexia nervosa (AN) as available findings on BDNF levels in patients with AN are ambiguous. AN is an eating disorder characterized by a pathological low body weight in combination with a body image disturbance typically developing during adolescence. A severe drive for thinness leads to restrictive eating behavior often accompanied by physical hyperactivity. During therapeutic weight restoration an increase of BDNF expression levels seems desirable as it might improve neuronal plasticity and survival which is essential for learning processes and thereby essential for the success of the psychotherapeutic treatment of patients. On the contrary, the well-known anorexigenic effect of BDNF might favor relapse in patients as soon as the BDNF levels significantly increase during weight rehabilitation. The present review summarizes the association between BDNF and general eating behavior and especially focuses on the eating disorder AN. In this regard findings from preclinical AN studies (activity-based anorexia model) are outlined as well.

A framework for conceptualising early intervention for eating disorders

OBJECTIVE

This paper outlines the evidence base for early intervention for eating disorders; provides a global overview of how early intervention for eating disorders is provided in different regions and settings; and proposes policy, service, clinician and research recommendations to progress early intervention for eating disorders.

METHOD AND RESULTS

Currently, access to eating disorder treatment often takes many years or does not occur at all. This is despite neurobiological, clinical and socioeconomic evidence showing that early intervention may improve outcomes and facilitate full sustained recovery from an eating disorder. There is also considerable variation worldwide in how eating disorder care is provided, with marked inequalities in treatment provision. Despite these barriers, there are existing evidence-based approaches to early intervention for eating disorders and progress is being made in scaling these.

CONCLUSIONS

We propose action steps for the field that will transform eating disorder service provision and facilitate early detection, treatment and recovery for everyone affected by eating disorders, regardless of age, socioeconomic status and personal characteristics.

Learned industriousness as a translational mechanism in anorexia nervosa

It remains unexplained why some behaviours persist despite being non-hedonic and ostensibly aversive. This phenomenon is especially baffling when such behaviours are taken to excess in the form of psychopathology. Anorexia nervosa is one psychiatric disorder in which effortful behaviours that most people find unpleasant (suchas restrictive eating) are persistently performed. We propose thatthe social psychology theory of learned industriousness providesa novel mechanistic account for such phenomena. This theoryposits that high-effort behaviour can be conditioned to acquire secondary reinforcing properties through repeated pairing with reward. Accordingly, effort sensations become less aversive andmore appetitive, increasing willingness to engage in effortful behaviour. In this Perspective, we review pre-clinical behaviouraland biological data that support learned industriousness, contrast learned industriousness with other models of non-hedonic persistence (such as habit learning), highlight evidence that supports learned industriousness in individuals with anorexia nervosa and consider implications of the model, including translation to other psychiatric presentations.

White matter microstructure in habit and reward circuits in anorexia nervosa: Insights from a neurite orientation dispersion and density imaging study

BACKGROUND

Behavioral features of anorexia nervosa (AN) suggest abnormalities in reward and habit. Neuroimaging evidence suggests morphometric and functional perturbations within these circuits, although fewer studies have assessed white matter characteristics in AN, and no studies to date have assessed white matter microstructure in AN.

METHODS

In this brain imaging study, 29 female adolescents with partially or fully weight-restored AN and 27 healthy controls, all between 10 and 19 years, underwent whole-brain multi-shell diffusion tensor imaging. Utilizing neurite orientation dispersion and density imaging methods, we investigated group differences in white matter neurite density, orientation dispersion, and myelin density in tracts between prominent nodes of the reward circuit (ventral tegmental area (VTA) to nucleus accumbens (NAcc)) and the habit circuit (sensory motor area [SMA] to putamen).

RESULTS

Findings revealed reduced neurite (F = 5.20, p = 0.027) and myelin density (F = 5.39, p = 0.025) in the left VTA-NAcc tract, and reduced orientation dispersion in the left (F = 7.00, p = 0.011) and right (F = 6.77, p = 0.012) VTA-NAcc tract. There were no significant group differences in the SMA-putamen tract. Significant relationships, after corrections, were not evident between tract microstructure and reward responsiveness, compulsive behaviors, illness duration, or BMI.

CONCLUSIONS

Adolescents with AN exhibit less dense, undermyelinated, and less dispersed white matter tracts connecting prominent reward system nodes, which could potentially signify underutilization of this part of the reward circuit. These results provide a detailed examination of white matter microstructure in tracts underlying instrumental behavioral phenotypes contributing to illness in AN.

Food Restriction in Anorexia Nervosa in the Light of Modern Learning Theory: A Narrative Review

Improvements in the clinical management of anorexia nervosa (AN) are urgently needed. To do so, the search for innovative approaches continues at laboratory and clinical levels to translate new findings into more effective treatments. In this sense, modern learning theory provides a unifying framework that connects concepts, methodologies and data from preclinical and clinical research to inspire novel interventions in the field of psychopathology in general, and of disordered eating in particular. Indeed, learning is thought to be a crucial factor in the development/regulation of normal and pathological eating behaviour. Thus, the present review not only tries to provide a comprehensive overview of modern learning research in the field of AN, but also follows a transdiagnostic perspective to offer testable explanations for the origin and maintenance of pathological food rejection. This narrative review was informed by a systematic search of research papers in the electronic databases PsycInfo, Scopus and Web of Science following PRISMA methodology. By considering the number and type of associations (Pavlovian, goal-directed or habitual) and the affective nature of conditioning processes (appetitive versus aversive), this approach can explain many features of AN, including why some patients restrict food intake to the point of life-threatening starvation and others restrict calorie intake to lose weight and binge on a regular basis. Nonetheless, it is striking how little impact modern learning theory has had on the current AN research agenda and practice.

Ketamine and Zinc: Treatment of Anorexia Nervosa Via Dual NMDA Receptor Modulation

Anorexia nervosa is a disorder associated with serious adverse health outcomes, for which there is currently considerable treatment ineffectiveness. Characterised by restrictive eating behaviours, distorted body image perceptions and excessive physical activity, there is growing recognition anorexia nervosa is associated with underlying dysfunction in excitatory and inhibitory neurometabolite metabolism and signalling. This narrative review critically explores the role of N-methyl-D-aspartate receptor-mediated excitatory and inhibitory neurometabolite dysfunction in anorexia nervosa and its associated biomarkers. The existing magnetic resonance spectroscopy literature in anorexia nervosa is reviewed and we outline the brain region-specific neurometabolite changes that have been reported and their connection to anorexia nervosa psychopathology. Considering the proposed role of dysfunctional neurotransmission in anorexia nervosa, the potential utility of zinc supplementation and sub-anaesthetic doses of ketamine in normalising this is discussed with reference to previous research in anorexia nervosa and other neuropsychiatric conditions. The rationale for future research to investigate the combined use of low-dose ketamine and zinc supplementation to potentially extend the therapeutic benefits in anorexia nervosa is subsequently explored and promising biological markers for assessing and potentially predicting treatment response are outlined.

Long-lasting BDNF signaling alterations in the amygdala of adolescent female rats exposed to the activity-based anorexia model

Introduction: Anorexia nervosa (AN) is a severe psychiatric disorder characterized by a pathological fear of gaining weight, excessive physical exercise, and emotional instability. Since the amygdala is a key region for emotion processing and BDNF has been shown to play a critical role in this process, we hypothesized that alteration in the amygdalar BDNF system might underline vulnerability traits typical of AN patients. Methods: To this end, adolescent female rats have been exposed to the Activity-Based Anorexia (ABA) protocol, characterized by the combination of caloric restriction and intense physical exercise. Results: The induction of the anorexic phenotype caused hyperactivity and body weight loss in ABA animals. These changes were paralleled by amygdalar hyperactivation, as measured by the up-regulation of cfos mRNA levels. In the acute phase of the pathology, we observed reduced Bdnf exon IX, exon IV, and exon VI gene expression, while mBDNF protein levels were enhanced, an increase that was, instead, uncoupled from its downstream signaling as the phosphorylation of TrkB, Akt, and S6 in ABA rats were reduced. Despite the body weight recovery observed 7 days later, the BDNF-mediated signaling was still downregulated at this time point. Discussion: Our findings indicate that the BDNF system is downregulated in the amygdala of adolescent female rats under these experimental conditions, which mimic the anorexic phenotype in humans, pointing to such dysregulation as a potential contributor to the altered emotional processing observed in AN patients. In addition, since the modulation of BDNF levels is observed in other psychiatric conditions, the persistent AN-induced changes of the BDNF system in the amygdala might contribute to explaining the onset of comorbid psychiatric disorders that persist in patients even beyond recovery from AN.

Altered Reinforcement Learning from Reward and Punishment in Anorexia Nervosa: Evidence from Computational Modeling

OBJECTIVES

Anorexia nervosa (AN) is associated with altered sensitivity to reward and punishment. Few studies have investigated whether this results in aberrant learning. The ability to learn from rewarding and aversive experiences is essential for flexibly adapting to changing environments, yet individuals with AN tend to demonstrate cognitive inflexibility, difficulty set-shifting and altered decision-making. Deficient reinforcement learning may contribute to repeated engagement in maladaptive behavior.

METHODS

This study investigated learning in AN using a probabilistic associative learning task that separated learning of stimuli via reward from learning via punishment. Forty-two individuals with Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 restricting-type AN were compared to 38 healthy controls (HCs). We applied computational models of reinforcement learning to assess group differences in learning, thought to be driven by violations in expectations, or prediction errors (PEs). Linear regression analyses examined whether learning parameters predicted BMI at discharge.

RESULTS

AN had lower learning rates than HC following both positive and negative PE (p < .02), and were less likely to exploit what they had learned. Negative PE on punishment trials predicted lower discharge BMI (p < .001), suggesting individuals with more negative expectancies about avoiding punishment had the poorest outcome.

CONCLUSIONS

This is the first study to show lower rates of learning in AN following both positive and negative outcomes, with worse punishment learning predicting less weight gain. An inability to modify expectations about avoiding punishment might explain persistence of restricted eating despite negative consequences, and suggests that treatments that modify negative expectancy might be effective in reducing food avoidance in AN.

Neural correlates associated with processing food stimuli in anorexia nervosa and bulimia nervosa: an activation likelihood estimation meta-analysis of fMRI studies

PURPOSE

Various neurobiological models have utilised symptom categories to explore the underlying neural correlates in both anorexia nervosa (AN) and bulimia nervosa (BN). The aim of this research was to investigate the brain activity patterns associated with viewing food stimuli in anorexia nervosa and bulimia nervosa.

METHODS

Electronic databases including PsycInfo and PubMed were systematically searched from data base inception until 1st of December 2020, identifying 14 suitable functional magnetic resonance imaging studies (fMRI), involving 470 participants. ALE meta-analysis was used to statistically analyse the overlap of activation foci from different fMRI studies in response to visual food stimuli.

RESULTS

Comparing patients with AN with healthy control (HC), we detected hypoactivation in brain areas related to reward processing (i.e., amygdala and lentiform nucleus), and interoceptive processing (i.e., insula). In addition, patients with AN showed hyperactivations in cognitive control areas (i.e., prefrontal and anterior cingulate cortex). In contrast, patients with BN exhibited hyperactivations in brain areas related to reward processing (i.e., lentiform nucleus), and interoceptive processing (i.e., insula). Furthermore, patients with BN showed hypoactivations in brain regions associated with cognitive control (i.e., prefrontal and anterior cingulate cortex).

CONCLUSIONS

Our study shows differing neural endotypes of the two types of eating disorders, that underpin their behavioural phenotypes. While exploratory in nature, these findings might be relevant for guiding new emerging therapies, including invasive and non-invasive neuromodulation techniques in treatment of eating disorders.

LEVEL OF EVIDENCE

Level I, meta-analysis.

Efficacy and safety of deep brain stimulation for treatment-refractory anorexia nervosa: a systematic review and meta-analysis

BACKGROUND

Several pioneering studies investigated deep brain stimulation (DBS) in treatment-refractory anorexia nervosa (AN) patients, but overall effects remain yet unclear. Aim of this study was to obtain estimates of efficacy of DBS in AN-patients using meta-analysis.

METHODS

We searched three electronic databases until 1st of November 2021, using terms related to DBS and AN. We included trials that investigated the clinical effects of DBS in AN-patients. We obtained data including psychiatric comorbidities, medication use, DBS target, and study duration. Primary outcome was Body Mass Index (BMI), secondary outcome was quality of life, and the severity of psychiatric symptoms, including eating disorder, obsessive-compulsive, depressive, and anxiety symptoms. We assessed the risk of bias using the ROBINS-I tool.

RESULTS

Four studies were included for meta-analysis, with a total of 56 patients with treatment-refractory AN. Follow-up ranged from 6-24 months. Random effects meta-analysis showed a significant increase in BMI following DBS, with a large effect size (Hedges's g = 1 ∙ 13; 95% CI = 0 ∙ 80 to 1 ∙ 46; Z-value = 6 ∙ 75; P < 0 ∙ 001), without heterogeneity (I²= 0 ∙ 00, P = 0 ∙ 901). Random effects meta-analysis also showed a significant increase in quality of life (Hedges's g = 0 ∙ 86; 95% CI = 0 ∙ 44 to 1 ∙ 28; Z-value = 4 ∙ 01, P < 0 ∙ 001). Furthermore, DBS decreased the severity of psychiatric symptoms (Hedges's g = 0 ∙ 89; 95% CI = 0 ∙ 57 to 1 ∙ 21; Z-value = 5 ∙ 47; P < 0 ∙ 001, I²= 4 ∙ 29, P = 0 ∙ 371).

DISCUSSION

In this first meta-analysis, DBS showed statistically large beneficial effects on weight restoration, quality of life, and reduction of psychiatric symptoms in patients with treatment-refractory AN. These outcomes call for more extensive naturalistic studies to determine the clinical relevance for functional recovery. This study is preregistered in PROSPERO,CRD42022295712.

Phonological working memory is adversely affected in adults with anorexia nervosa: a systematic literature review

PURPOSE

Cognitive restraint has potentiating and deleterious effects on working memory (WM) in anorexia nervosa (AN). Conflicting evidence may be due to heterogeneity of tasks examining different WM components (e.g., verbal/auditory versus visuospatial), and differences in adolescent versus adult AN. Additionally, differential cognitive profiles of restricting versus binge/purging subtypes, comorbid psychiatric disorders and psychotropic medication use may confound findings.

METHODS

To address these conflicts, 25 studies, published between 2016 and 2021, investigating WM in children, adolescents and adults with AN were systematically reviewed using PRISMA guidelines.

RESULTS

In 71% of WM tasks, no difference in performance between AN patients and age-matched controls was reported, while 29% of WM tasks showed worse performance. Adults with AN displayed deficits in 44% of the verbal/auditory tasks, while performance remained unaffected in 86% of visuospatial tasks.

CONCLUSION

Examining age groups and WM subsystems separately revealed novel findings of differentially affected WM components in AN. Comorbidities and psychotropic medications were common among AN participants and should be regarded as critical confounding factors for WM measures. Future studies examining different components of WM, acknowledging these confounding factors, may reveal specific deficits in AN to aid treatment improvement strategies.

LEVEL OF EVIDENCE

I, systematic review.

Responding to "Terminal anorexia nervosa: three cases and proposed clinical characteristics"

The treatment of eating disorders raises many ethical debates given the pervasiveness with which this illness impacts individuals, especially as the length of time with the illness increases. A recent case study supported the appropriateness of pursuing medical aid in dying for individuals with eating disorders who wish to end their fight with their disorder. This correspondence raises concerns related to this controversial proposal as the current authors dispute that the use of medical aid in dying for individuals with eating disorders is ethically judicious or appropriate. Additionally, this correspondence highlights additional treatment implications that should be considered when trying to provide individuals with eating disorders with the best evidence-based care possible, with the goal of promoting steps toward recovery.

How Can Animal Models Inform the Understanding of Cognitive Inflexibility in Patients with Anorexia Nervosa?

Deficits in cognitive flexibility are consistently seen in patients with anorexia nervosa (AN). This type of cognitive impairment is thought to be associated with the persistence of AN because it leads to deeply ingrained patterns of thought and behaviour that are highly resistant to change. Neurobiological drivers of cognitive inflexibility have some commonalities with the abnormal brain functional outcomes described in patients with AN, including disrupted prefrontal cortical function, and dysregulated dopamine and serotonin neurotransmitter systems. The activity-based anorexia (ABA) model recapitulates the key features of AN in human patients, including rapid weight loss caused by self-starvation and hyperactivity, supporting its application in investigating the cognitive and neurobiological causes of pathological weight loss. The aim of this review is to describe the relationship between AN, neural function and cognitive flexibility in human patients, and to highlight how new techniques in behavioural neuroscience can improve the utility of animal models of AN to inform the development of novel therapeutics.

Behavioral reinforcement of pathological exercise in anorexia nervosa

Pathological exercise in anorexia nervosa (AN) is a harmful behavior associated with a chronic course and poor prognosis. To date, no comprehensive theoretical model exists to describe pathological exercise in the context of AN, and as such, few treatments are effective at promoting direct and sustained pathological exercise extinction. Using a framework put forth by Wise & Koob (2014), debating the relative importance of positive and negative reinforcement in substance use, we present three hypotheses of behavioral reinforcement of exercise, encompassing biological, psychological, and environmental influences. Specifically, we argue that exercise is positively reinforced through receipt of biological and behavioral rewards, negatively reinforced through avoidance of aversive emotions, and that these two systems work in tandem over time to engrain pathological exercise as a habit. We then present suggestions for testing each of these hypotheses as future directions for the field.