Background: A prevalence of non-suicidal self-injury is not easily assessed; however, meta-analyses found a lifetime prevalence of 17% in non-clinical student samples. This estimate increases to 50-74% in psychiatric populations. Non-suicidal self-injury is an important predictor for later suicidal behavior and death by suicide. Although non-suicidal self-injury is highly prevalent, there is no evidence for specific treatment for non-suicidal self-injury in adolescents. Reviews find that internet-based interventions guided by a therapist are effective for several psychiatric disorders such as anxiety and depression in adult population. Patients with stigmatizing illnesses such as non-suicidal self-injury may be reluctant to seek help and adhere with treatment while internet-based interventions are more appealing. There is a need for trials investigating the effect of specialized interventions for non-suicidal self-injury in youth, including digital interventions.~Objective: To investigate the effect of an internet-based intervention, Emotion Regulation Individual Therapy for Adolescents (ERITA), as add-on to treatment as usual in 13-17-year-old patients with non-suicidal self-injury referred to Child- and Adolescent Mental Health Services with subsequent non-suicidal self-injury as primary outcome assessed by Deliberate Self-Harm Inventory - Youth. Further clinical outcomes such as quality of life, depression, anxiety and stress, as well as emotion regulation difficulties will be assessed as secondary outcomes.~Method and materials: This is a randomized, clinical, superiority, multicenter trial in a parallel group design. Patients will be recruited from Child- and Adolescent Mental Health Services in three of the Danish Regions: The trial inclusion period will be from primo 2022 to ultimo 2023. The experimental intervention is therapist guided internet-based ERITA provided exclusively online as add-on to treatment as usual in the experimental group. Treatment as usual is provided by multidisciplinary teams in outpatient clinics in all participating regions. We expect to include 356 participants and one of their parents.
Emotion Regulation Individual Therapy for Adolescents, also called ERITA, is a youth friendly online therapy aiming to provide skills and train emotion regulation.~The aim of the TEENS Multi-site Trial is to investigate the effect of ERITA, including an app, as add-on to treatment as usual in young patients referred to Mental Health Services. We expect 356 families to participate from three designated Regions in Denmark.