Using Mentalization Based Therapy to Support Children and Adolescents Referred to Specialist Mental Health Services in the NHS for Aggressive and/or Violent Behaviour

The primary outcome is aggression and violent behaviour measured by the self-reported Reactive and Proactive Aggression Questionnaire. The RPQ combines two subscales, one measuring reactive aggression (12 items), the other proactive aggression (11 items). Each item is scored on a three-point scale from 0 (never) to 2 (often). Item scores from each subscale are added together to produce sub-scale scores (range 0-24 for reactive aggression, and 0-22 for proactive aggression). The total score can range from 0-46.

Five outcomes will be measured using the 30-item Strengths and Difficulties Questionnaire including impact supplement: conduct problems using the conduct problem subscale (5 items); inattention difficulties using the hyperactivity/inattention subscale (5 items); emotional difficulties using the emotional symptoms subscale (5 items); difficulties with peers using the peer relationship problems scale (5 items). Each item is rated on a 3-point scale: Not True = 0, Somewhat True = 1, and Certainly True = 2. For each subscale, scores range from 0 to 10, with higher scores reflecting more difficulties.

The impact supplement asks participants whether they experience difficulties in emotions, behaviour, concentration, or relationships rated from 'no' to 'severe difficulties'. Further questions ask about interference of these difficulties in areas of life including home, friendships, learning and leisure, rated from 'not at all' to 'a great deal'.

Two outcomes will be measured to assess mentalizing using two subscales (10 items) of the Emotion Awareness Questionnaire:

• Analyses of emotions (5 items, score 5-15) (sample item: "When I am angry or upset, I try to understand why").
• Attending to others' emotions (5 items, score 5-15) (sample item: "It is important to know how my friends are feeling").

For items in both subscales, responses are scored on a three-point scale from 1 (not true) to 3 (often true).

One family outcome will be measured using the total score of the SCORE-15, a 15-item self-report measure designed to assess perceived family functioning across emotional, behavioral, and communication areas. Participants are asked to indicate how well each statement describes their family using a 5-point scale between the range: 1 (Describes us: Very well) to 5 (Describes us: Not at all).

In addition to the 15-item quantitative scale, the SCORE-15 includes two open-ended, qualitative questions i.e. "What words would best describe your family?" and "What is the problem/challenge that brought you to therapy?".

Lastly, the SCORE-15 includes three single-item visual analogue scales designed to capture subjective ratings of severity of difficulties (scale of 0 [No problem at all] to 10 [Really bad]), family managing (scale of 0 [very well] to 10 [very badly]), and perceived helpfulness of therapy (scale of 0 [very helpful] to 10 [unhelpful]).

One outcome, aggression and violent behaviour, will be measured using a parent/carer version of the RPQ. The RPQ is a 23-item self-report questionnaire designed to assess two subtypes of aggressive behaviour: reactive aggression (12 items) and proactive aggression (11 items). Each item is rated on a 3-point scale indicating frequency of behaviour (0 = Never, 1 = Sometimes, 2 = Often). Subscales range from 0-24 (reactive) and 0-22 (proactive). The total aggression score ranges from 0-46.

Five outcomes will be measured using the 30-item parent version of the Strengths and Difficulties Questionnaire including impact supplement: conduct problems using the conduct problem subscale (5 items); inattention difficulties using the hyperactivity/inattention subscale (5 items); emotional difficulties using the emotional symptoms subscale (5 items); difficulties with peers using the peer relationship problems scale (5 items). Each item is rated on a 3-point scale: Not True = 0, Somewhat True = 1, and Certainly True = 2. For each subscale, scores range from 0 to 10, with higher scores reflecting more difficulties.

The impact supplement asks participants whether their child experiences difficulties in emotions, behaviour, concentration, or relationships rated from 'no' to 'severe difficulties'. Further questions ask about interference of these difficulties in areas of life including home, friendships, learning and leisure, rated from 'not at all' to 'a great deal'.

One family outcome will be measured using the total score of the SCORE-15 as reported by parents/carers. SCORE-15 is a 15-item self-report measure designed to assess perceived family functioning across emotional, behavioural, and communication areas. Participants are asked to indicate how well each statement describes their family using a 5-point scale between the range: 1 (Describes us: Very well) to 5 (Describes us: Not at all).

In addition to the 15-item quantitative scale, the SCORE-15 includes two open-ended, qualitative questions i.e. "What words would best describe your family?" and "What is the problem/challenge that brought you to therapy?".

Lastly, the SCORE-15 includes three single-item visual analogue scales designed to capture subjective ratings of severity of difficulties (scale of 0 [No problem at all] to 10 [Really bad]), family managing (scale of 0 [very well] to 10 [very badly]), and perceived helpfulness of therapy (scale of 0 [very helpful] to 10 [unhelpful]).

Six child outcomes will be measured using six items of the Health of the Nation Outcomes Scales for Children and Adolescents (HoNOSCA) reported by a clinician:

Disruptive, antisocial or aggressive behaviour; Non accidental self-injury; Substance misuse; Peer relationships; Family life and relationships; School attendance.

Each item is scored from 0 (no problem) to 4 (severe to very severe problem), with higher scores indicating greater severity. A score of 3 or above on any item indicates a moderate to severe problem.

Therapeutic alliance, as a potential mediator or mechanism of change, will be assessed in the intervention arm at three timepoints (early therapy e.g. session 1-3, mid-therapy e.g. session 10-13, and late therapy e.g. session 20-24) using the Session Rating Scale (SRS). The SRS assesses the young person's perceptions of: respect and understanding from the clinician, how much they talk about the topics that matter to them, the clinicians approach or method, and overall acceptability of the session. A visual line is presented with contrasting statements at each e.g. "I did not feel heard, understood and respected", versus "I felt heard, understood and respected", (on the SRS version for 6-12 year olds, the statements are supplemented with a sad face or smiley face, respectively). Participants indicate their experience by placing a mark somewhere along the line. Reponses marked closest to the positive version of the statement (the smiley face) indicate a better therapeutic alliance.

Progress towards goals, as a potential mediator or mechanism of change, will be assessed in the intervention arm at three timepoints (early therapy e.g. session 1-3, mid-therapy e.g. session 10-13, and late therapy e.g. session 20-24) using the goal based outcome (GBO) tool. The GBO enables young people to set up to three goals and rate the extent to which they feel that they have reached their goals on a scale of 0 (no progress) to 10 (fully reached).