After the COVID-19 pandemic, patients with eating disorders have been reported that social isolation, worsening of symptoms, and an increase in new patients and hospitalization. We investigated the number of new patients and hospitalized patients with AN and ARIFD, sex, and age groups in Japan in 2019, 2020, and 2021. The current study is a multicenter retrospective survey. The Ethics Dokkyo Medical University Committee approved this study, conducted at Saitama Medical Center (22001). Results from 28 centers that responded to all items were tabulated and analyzed. The total number of hospitalized/new patients with AN was 266/400 in 2019, 266/480 in 2020, and 309/610 in 2021. The total number of hospitalized/new patients with ARFID patients was 15/70 in 2019, 22/97 in 2020, and 17/112 in 2021. Both AN and ARFID showed an increasing trend in 2020 and 2021 compared to 2019; interestingly, the number of patients increased in 2021 compared to 2020. The increase in AN and ARFID was more pronounced among younger females, which supported previous reports. On the other hand, hospitalization rates decreased chronologically. The fact of many ARFID patients may have increased after the pandemic, compared to previous reports, is a novel finding.

In recent years, the link between developmental disorders and eating disorders has gradually become clearer. Many patients with eating disorders have features of autism spectrum disorder (ASD), and the sensory issues and preoccupations of ASD may be linked to eating disorder symptoms. Symptoms of attention-deficit/hyperactivity disorder are also associated with eating disorders, particularly impulsivity, which is associated with overeating behavior. However, a causal relationship that developmental disorders are the cause of eating disorders is not known. It is also not known whether developmental disorders are a specific or nonspecific predisposition to eating disorders. In addition, while there is a growing number of reports of common features shared by developmental disorders and eating disorders, few studies have examined the effects of other comorbidities. In actual clinical practice, we need to be mindful of these unexplored aspects of previous research in our evaluation, diagnosis, and treatment. And we need to conduct new studies to address the issues raised by these previous studies.

Background: Since the end of the twentieth century, the relationship between eating disorders and dissociation has been discussed, and in recent ten years, the number of papers reporting the relationship between eating disorders and trauma has increased. We need new therapeutic strategies for eating disorders with trauma or dissociation because it is challenging to treat such diseases using existing treatments.

Subjects and Methods: This study examined academic papers on the relationships between eating disorders and trauma or dissociation in these thirty years using PubMed to elucidate the psychopathology of comorbidity of these diseases and determine appropriate treatment strategies.

Results: According to the literature, about twenty percent of patients with anorexia nervosa and thirty to sixty percent with bulimia nervosa also have post-traumatic stress disorder (PTSD), and three to nine percent of individuals without eating disorders have PTSD; specifically, bulimic symptoms and PTSD share a close relationship. Furthermore, people who have undergone abuse during childhood tend to suffer from eating disorders about three times as much as others. Numerous researchers have pointed out the relationships between trauma and overeating or vomiting, such as the relationship between sexual assault in adulthood and binge/purging, sexual abuse in childhood and disordered eating, and adverse experiences in childhood and emotional eating induced by stress. Generally, past traumatic experiences cause negative feelings, such as fear, shuddering, anger, guilt feeling, or shame; more frequent overeating leads to stronger negative feelings. Therefore, overeating could be a method to control emotions. As patients with eating disorders have an insecure type of attachment, they tend to have interpersonal anxiety, which could lead to difficulty in regulating feelings and a tendency to be dissociative. In order to treat eating disorders with trauma or dissociation or, it has been tried to integrate the cognitive behavioral therapy (CBT) for eating disorders and the CBT for PTSD, such as cognitive process therapy (CPT).

Discussion: It can be challenging to treat eating disorders with PTSD or dissociation only by means of the existing CBT for eating disorders because the psychopathology of such eating disorders is too complexed. In any therapy, it is crucial to establish a relationship of mutual trust between therapist and patient, and create a secure therapeutic environment.

Research attempts at elucidating the pathophysiology of eating disorders such as anorexia nervosa and bulimia nervosa have been progressing through brain functional imaging studies. The dorsolateral prefrontal cortex serves as the center for the cognitive control system, aggregating spatial information and hippocampal memory information to plan rational behavior. The orbitofrontal cortex forms the reward system, evaluating the value of recognized objects based on information from the amygdala’s emotional signals. Several reports have indicated hyperactivity in the dorsolateral prefrontal cortex during various tasks in patients with anorexia nervosa, suggesting that excessive cognitive control may give rise to rigid behaviors. In the case of the orbitofrontal cortex, increased activation concerning food has been observed. Additionally, functional abnormalities in the insular cortex, which connects interoceptive sensations, emotions, the cognitive control system, and the reward system, as well as abnormalities in the medial prefrontal cortex associated with introspection, have also been identified. However, previous research suffered from limited sample sizes, which posed constraints on reliability and reproducibility. Therefore, collaborative multi-center research efforts for unraveling the neural basis of eating disorders are currently underway in Japan.