The goal of this feasibility study is to evaluate the feasibility and preliminary clinical outcomes of a personalized digital treatment for adolescents with eating disorders. The main objectives are to:

i) Evaluate whether a personalized digital treatment for adolescents with eating disorders are feasible in a child and adolescent psychiatric outpatient clinic.

ii) Evaluate who benefits from a personalized digital treatment for adolescents with eating disorders (what works for whom?) iii) Evaluate the cost-benefit of a personalized digital treatment for adolescents with eating disorders.

Participants will be enrolled in a 10-week digital treatment including weekly therapist contact. They will be asked to complete self-report questionnaires at pre-, during, post- and 3- and 6-months follow-up.

Eating disorders are associated with high levels of distress, significant somatic problems, and high mortality. The difficulties have significant consequences for the individual, family members, and society at large. Early treatment leads to better prognosis, but the identification and treatment of eating disorders are challenging within the healthcare system. The effect of digital treatments for patients with eating disorders appears promising.

In this study, we will investigate the feasibility and preliminary effects of therapist-guided digital treatment for youth with eating disorders using qualitative and quantitative methods. The project uses the Person-based approach (PBA) as methodological framework, which is an evidence-based method for developing user-centered and effective behavior change interventions.

The study wants the examine the intervention within six feasibility domains that includes the following research questions:

Feasibility domain 1. Sample distribution of general psychopathology of eating disorder symptoms:

A. Will a reasonable wide spectrum of individuals with different forms of eating disorders show interest and be eligible? B. Will 60 adolescents be eligible over the course of one year? C. What characterizes the group that participate (predictor)?

Feasibility domain 2. Adherence to the treatment protocol:

A. Do 50% of the adolescents complete the entire intervention? B, What characterizes those who carry out the treatment (predictor)? C. What characterizes those who drop out (predictor)?

Feasibility domain 3. Treatment credibility:

A. Will 70% of the participants rate the treatment as acceptable/recommend it to a friend?

Feasibility domain 4. Treatment acceptability:

A. What are the adolescents' experiences of a personalised digital treatment targeting eating disorders?

Feasibility domain 5. Treatment use and utility:

A. Will a moderate within-group effect, around d=0.50, be seen on general psychopathology of eating disorder? B. Will more than 40% of the sample obtain a significant reliable change on primary outcome? C. Will less than 10% of the sample experience negative effects and/or deterioration defined as a negative significant reliable change?

Feasibility domain 6. Treatment cost-effectiveness:

A. What is the cost-effectiveness of a personalized digital treatment for for adolescents with eating disorders in routine care?

Youth between the ages of 16-18 with an eating disorder will be invited to participate in this intervention study. The participants will be recruited via child and youth psychiatric outpatient clinics and social and media. Eligible participants get access to an online information consent form which is signed digitally using the Norwegian electronic identification system BankID.

Data will be collected using self-report questionnaires administrated online at pre-, during, post- and 3- and 6-months follow-up. All measures are previously validated and have been used in eating disorder adolescent populations. Based on the literature potential predictors are included in the study protocol. The pre-treatment symptoms variables are associated with external clinical features, which maintain an eating disorder. The predictor variables will be collected pre-treatment.

We will conduct semi-structured phone interviews to explore the patients' in-depth experience of the digital treatment. The interviews of approximately 16 adolescents will be conducted 2-4 weeks after finishing the treatment. We will strive to have two groups, one with participants that finished the treatment, and one with dropouts.

Inclusion Criteria:

A. Diagnosed with F50.1 Atypical anorexia nervosa, F50.3 Atypical bulimia nervosa, F50.8 Other eating disorders, F50.9 Eating disorder, unspecified

B. Age between 15 and 18 years.

C. Stable dose of medication for a co-morbid psychiatric treatment for six weeks and who continue to meet study entry criteria.

D. Internet access.

E. Speaks and write Norwegian.

Exclusion Criteria:

A. Diagnosed with F50.0 Anorexia nervosa or F50.2 Bulimia nervosa

B. Disorders of psychological development (F80-F89).

C. Patients with avoidant restrictive food intake disorders (F50.82)

D. Participants with a co-morbid medical condition or disorder known to influence eating or weight (i.e., pregnancy, cancer), psychotic disorders, acute suicidality, or substance abuse and/or substance dependence and severe depressive episode.

E. Receiving inpatient- or face to face psychological treatment.