Effects of Internet-based ERITA Added to TAU in Young People With Non-Suicidal Self-Injury (TEENS) Feasibility Trial

Completion of follow-up will be defined as completing at least one clinical outcome (non-suicidal self-injury events) at end of intervention. If the number participants with completed outcomes is 26 out of 30, the fraction will be 87%, 95% CI 75% to 99%. A follow-up fraction of 87% or more will be acceptable for a future trial while a fraction below 75% will impose serious problems of interpreting the trial result in a future large pragmatic trial.

We will determine the fraction of potential participants as the number of eligible persons compared to the number of randomized persons. If the number of participants randomized out of the number of eligible persons is 30 out of 75, the fraction will be 40%, 95% confidence interval (CI) will be: 29% to 51%. A randomization fraction of 29% or more will be acceptable for a future trial, while a fraction below 29% will impose serious problems of recruitment for a future large pragmatic trial.

Compliance with the experimental intervention will be defined as completing at least six of 12 ERITA sessions. ERITA will automatically register time for login and save the exercises that have been completed. If the number of compliant experimental participants is 11 out of 15, the fraction will be 73%, 95% CI 51% to 96%. A compliance fraction of 51% or more will be acceptable for a future trial while a fraction below 51% will impose serious problems of interpreting the trial result in a future large pragmatic trial.

Non-suicidal self-injury, assessed at baseline and end of therapy (12 weeks) by blinded outcome assessment by phone with Deliberate Self-Harm Inventory (DSHI-Y)

Quality of life at 12 weeks, assessed with Kidscreen-10. 5-point Likert scale, range: not at all, a little, modearte, much, very much.

Symptoms of depression, anxiety and stress at 12 weeks, assessed with Depression Anxiety Stress Scale (DASS-21). 4-point Likert scale, range: did not apply to me, applied to me to some degree, applied to me to a considerable degree, applied to me much/most of the time. Totale range for subscores: 0-42. Higher scores reflects worse outcome.

Non-suicidal self-injury as dichotomous variables (Yes/No)

Number of sick days the last month

Difficulties in emotion regulation, assessed weekly during 12 weeks with Difficulties in Emotion Regulation Scale (DERS-16). 5-point Likert scale, range: almost never, some times, half of the time, most of the time, all the time. Total scores range from 16 to 80, with higher scores reflecting grater levels of emotion dysregulation.

Indirect self-destructive behaviours at 12 weeks, assessed with Borderline Symptom List (BSL-supplement). 5-point Likert scale, range: not at all, once, 2-3 times, 4-6 times, daily or more often. Total scores range from 0-44 and higher scores reflect worse outcome.

Suicidal ideations, plans and actions at 12 weeks, assessed with Columbia (C-SSRS). Dichotomous outcome yes/no; if yes intensity is rated on a 5-point Likert scale, total score range: 2-25. Higher scores reflect worse outcome.

Adolescent's perception of Parents' ability to cope with children's negative emotions at 6 weeks and 12 weeks, assessed with The Coping with Children's Negative Emotions Scale (CCNES-APP). 7-point Likert scale, Range from very unlikely to very likely. Six Sub scales with total score range: 0-42. The sub scale are inversely related.

Parents' perceived ability to cope with children's negative emotions at 6 weeks and 12 weeks, assessed with The Coping with Children's Negative Emotions Scale Adolescent (CCNES-A). 7-point Likert scale, Range from very unlikely to very likely. Six Sub scales with total score range: 0-42. The sub scale are inversely related.

Adverse Events 4, 8 and 12 weeks assessed with Negative Effects Questionnaire (NEQ). Dichotomous outcomes as yes/no; if yes then a 5-point Likert scale of the impact, range not at all, a little, moderately, much, very much. The total score range 0-80. Higher scores reflect worse outcome.

Strengths and difficulties assessed by Strengths and difficulties questionnaire (SDQ) at 4, 8, and 12 weeks. 3-point Likert scale, range: doesn't fit, fits moderately, fits very much. Total score range 0-40. Sub scales of strengths and difficulties that are inversely related.

Working alliance with online therapist assessed with Working Alliance Inventory (WAI-SR). 5-point Likert scale, range: seldom, some times, fairly often, very often, always. Total score range 12-60. Higher scores reflect higher working alliance/better outcome.