A Digital Treatment for Adolescents With Eating Disorders

The Credibility and Expectancy Scale (CEQ-1)

CEQ-1 will be used after participants have completed the first module of the treatment. CEQ measures perceived treatments credibility. We will use 1-item "How confident would you be in recommending this treatment to a friend who experiences similar problems?" The item is rated on a scale from 0 to 10, where higher score indicates better treatment credibility.

Adherence

Adherence (dropout rates and completion of modules) will be used to assess the acceptability of the intervention. The total number of logged on sessions during the intervention period will be collected, and the average length of sessions. Days in treatment will be calculated based on the dates between the first login, and the completion of the last module.

Module evaluations

After each treatment module the participants will be asked to evaluate the module which will be used to assess acceptability of the intervention. With a 6-item self-report questionnaire assessed on a 5-point Likert scale ranging from "completely disagree" to "completely agree".

Client Satisfaction Questionnaire (CSQ-3)

Intervention satisfaction will be measured at post-treatment, using the 3-item Client Satisfaction Questionnaire (CSQ-3) CSQ-3 are items 3, 7, \& 8 from the CSQ-8. Each item on the CSQ-3 is scored from 1 to 4, where a higher score indicate higher satisfaction.

The Patient Health Questionnaire (PHQ-2)

The Patient Health Questionnaire (PHQ-2) are used for assessing depression. The PHQ-2, comprising the first 2 items of the PHQ-9, inquiries about the degree to which an individual has experienced depressed mood and anhedonia over the past two weeks. Items are rated on scale from 1 to 4, where a higher rating indicate higher degree of depressed mood.

Generalized Anxiety Disorder scale (GAD-2)

Generalized Anxiety Disorder scale (GAD-2) is used for assessing anxiety disorders. The GAD-2 is a quick version of the seven-item scale that incorporates the first two questions of the GAD-7, which are also critical components of any anxiety disorder.Items are rated on scale from 1 to 4, where a higher rating indicate higher degree of anxiety.

School attendance

In addition, we will collect School attendance (variables: full-time/reduce-time/don't attend school/ don't attend school but have a job) to assess quality of life.

Tme with friends

Time with friends with the categories: daily/weekly/monthly/don't have friends/ don't have time to friends because of my eating disorder, will also be used to assess quality of life.

The Rosenberg Self-Esteem Scale (RSES)

The Rosenberg Self-Esteem Scale (RSES) to measure self-esteem, a maintaining mechanism. RSES is a widely used 10-item self-report questionnaire. Items are answered on a 4-point scale, ranging from 3 (strongly agree) to 0 (strongly disagree). Scores range from 0 to 40, and higher scores indicate higher global self-worth.

The readiness to change questionnaire (RTCQ-6)

The readiness to change questionnaire (RTCQ-6) is adapted to the study population and digital treatment inspired by the Short Motivation Feedback List (SMFL-8).

Qualitative interviews

Qualitative interviews will be conducted following the intervention with 16 participants. We will aim to recruit both treatment completers and treatment dropouts.