Blended Unified Protocol in Chinese Adolescents With Non-Suicidal Self-Injury

Adherence to the intervention will be measured by the number of sessions attended and the number of participants who complete at least 70% of the sessions, the timing of these sessions (within the designated week or not), the number of interactive exercises completed in each session, and the completion of home assignment tasks.

Dropout rates are defined as the number of participants who dropped out from the intervention before completing it.

The FAQ will be used to evaluate the feasibility and acceptability of the intervention. The FAQ consists of three subscales, each containing six items: (1) experience using the online platform, (2) satisfaction with the program, (3) therapeutic alliance. The higher scores indicate greater feasibility and acceptability.

Participants' perspectives on the intervention will be assessed through semi-structured interviews, exploring the factors that facilitate or hinder their adherence to and completion of the program.

The Adolescent Self-Harm Behavior Scale includes 18 items describing forms of self-harm. The scale is divided into two dimensions: frequency and severity of self-harm. Self-harm frequency is scored on a 4-point scale (0-3), with the following categories: 0 times, 1 time, 2-4 times, and more than 5 times. The severity of physical injury is scored on a 5-point scale (0-4), with the following categories: none, mild, moderate, severe, and extremely severe. The product of frequency and injury severity for each item is used as the overall score for NSSI, with higher scores indicating more severe NSSI behavior.

Difficulties in Emotion Regulation Scale (DERS) is used to assess the participants' emotional regulation abilities. It consists of 36 items across 6 dimensions, with higher total scores indicating a higher level of emotional dysregulation. The dimensions include: emotional awareness, emotional acceptance, impulse control, emotional understanding, goal-directed behavior, and strategy use.

The Emotion Regulation Questionnaire (ERQ) is used to measure participants' emotional regulation strategies. It consists of 10 items, divided into two dimensions: cognitive reappraisal and expressive suppression. Each item is rated on a 7-point scale, with higher scores indicating a stronger tendency to use the corresponding emotional regulation strategy.

The Patient Health Questionnaire-9 (PHQ-9) was used to measure depression levels. This nine-item scale rates each item on a four-point scale from 0 ("not at all") to 3 ("nearly every day"), with total scores ranging from 0 to 27. Higher scores indicate greater depression severity.

The Generalized Anxiety Disorder-7 (GAD-7) was used to assess anxiety levels of participants. This seven-item scale also employs a four-point scoring system from 0 ("not at all") to 3 ("nearly every day"), with higher scores reflecting greater anxiety severity.

The Basic Psychological Need Satisfaction and Frustration Scale (BPNSF) was developed by Chen in 2015. The scale consists of two subscales: basic psychological need satisfaction and basic psychological frustration. The Basic Psychological Need Satisfaction subscale includes three dimensions-autonomy satisfaction, competence satisfaction, and relatedness satisfaction-comprising 12 items in total. The Basic Psychological Need Frustration subscale includes three dimensions-autonomy frustration, competence frustration, and relatedness frustration-also comprising 12 items. Participants are asked to rate each item on a 5-point Likert scale (1 = Strongly Disagree; 5 = Strongly Agree).

The Neuroticism subscale from the Neuroticism-Extraversion-Openness Five-Factor Inventory was selected to measure neuroticism. The Neuroticism subscale consists of 12 items, rated on a 5-point Likert scale. Higher scores indicate a stronger tendency toward neuroticism in the individual.

The Distress Tolerance Scale (DTS) is a 15-item measure of an individual's perceived ability to withstand negative emotions. Items are answered on a five-point Likert scale ranging from 1 = strongly agree to 5 = strongly disagree. Traditionally, high DTS-global distress intolerance scores reflect a heightened ability to tolerate distress, whereas low total scores represent distress intolerance.