Cognitive behavioral therapy (CBT) for patients with bulimia nervosa (BN) or binge eating disorder (BED) has been shown to be effective. CBT is one of the most evidence-based psychological interventions for BN or BED. And therefore, guidelines for eating disorders (ED) generally recommend CBT for the treatment of BN or BED. However, CBT is not as widely utilized as it should be, as there is a shortage of therapists with the necessary training, and their training and the length of time required for treatment are not economically viable.
 Although the prevalence of BN is on the rise, delays in treatment initiation and high treatment dropout rates have been pointed out. It is understood that the earlier the treatment of BN is started, the higher is the rate of improvement. In addition, BN has a high suicide rate. So, prevention of the onset of BN and early initiation of treatment are crucial issues.
 The necessity of developing a CBT that is highly practical and acceptable for treatment is clear. Several guidelines recommend guided self-help as a simple, low-cost, and low-intensity treatment method with good therapeutic effects in the treatment of BN and BED. In addition, an increasing number of studies on internet-based treatment interventions for mental health problems have been conducted in recent years, suggesting that online interventions may be more cost-effective, convenient, and accessible to more people. Internet-based cognitive behavioral therapy (iCBT) for BN has been examined for its efficiency and its therapeutic effect is eagerly anticipated. The NICE guideline (2017) and several other guidelines recommend the internet guided self-help cognitive behavioral therapy (iGSH-CBT) as a first-line treatment for BN and BED. In this article, we will report evidence as well as the status of the development of iGSH-CBT in Japan.
 Authors' abstract