A Mentalization Based Prevention Program to Foster Well-Being and Mental Health in Pre-Adolescent Children and Their Families

To assess children's well-being, the KIDSCREEN10 Index will be used both as a self-report completed by the children and as an external proxy report provided by their parents. Responses are recorded on a 5-point Likert scale ranging from 1 (not at all/never) to 5 (very much/always). The ten items on mental health are summed up to yield a total score ranging from 10 to 50, where lower scores indicate poorer mental health and higher scores reflect better mental health.

The Strengths and Difficulties Questionnaire (SDQ) will be used to assess mental health difficulties in children. The SDQ is completed as an external proxy report by parents and consists of 25 items, which are distributed across five subscales: Emotional Symptoms, Conduct Problems, Hyperactivity/Inattention, Peer Relationship Problems, and Prosocial Behavior. Items are rated on a 3-point Likert scale ranging from 0 (not true) to 2 (certainly true). For each subscale, items scores are summed to yield a total score. Additionally, a Total Difficulties Score is calculated by summing the scores of the first four subscales, whereas the Prosocial Behavior subscale is analyzed separately. Higher scores on the Total Difficulties Scale indicate increased behavioral and emotional challenges, whereas higher scores on the Prosocial Behavior subscale reflect stronger social competencies.

Well-being of parents will be measured using the European Quality of Life 5 Dimensions 5 Level Version. Parents assess their level of well-being across five dimensions: Mobility, Self-care, Usual activities, Pain/Discomfort, and Anxiety/Depression. Response options include: no, slightg, moderate, severe, extreme problems. Additionally, participants complete a scale on which they can rate their current health from 0-100, with 100 being the best possible health and 0 the worst possible health. Scores for the five-dimensional scale will be summed and treated separately to the health-scale score.

The Depression, Anxiety and Stress Scale-Short Version will be used to assess mental health in parents over the past seven days based on severity. The 21 items are divided into three 7-item subscales, each representing one of the emotional states. The items are rated on a 4-point Likert-type scale ranging from 0 (Does not apply to me at all) to 3 (Applied to me very much or most of the time). The severity score for each subscale is calculated by summing the valid item scores and multiplying the result by two.

The Positive Mental Health Scale for children and adolescents (PMH-Kids) measures positive mental health in children and adolescents between 6 and 18 years old. The scale consists of 9 self-reported items. The items are rated on a 4-point Likert-type scale ranging from 0 (do not agree) to 3 (totally agree). The total score ranges from 0 to 27 with higher scores representing a higher degree of positive mental health.

The Peer Mental Health Stigmatization Scale (PMHSS) will be used to assess stigmatizing attitudes towards children with mental health. The questionnaire comprises 11 items rated on a 5-point Likert scale ranging from 1 (strongly agree) to 5 (strongly disagree).The total stigma score is calculated by summing responses across all items. The resulting scores range from 11 to 55, whereby a lower score indicates a higher level of stigmatization.

The Actual Help-Seeking Questionnaire will be used to assess actual help-seeking behavior. Children will be asked to tick resources from a provided checklist of 8 potential resources from whom they have sought help in the past six months because they experienced a mental health problem. In addition, they will have the option to add a person not listed, to indicate that they did not seek help from anyone, and to indicate that they did not have a mental health problem in the past six months.

The Positive Mental Health Scale (PMH) will be used to assess positive mental health in parents. The scale consists of 9 self-reported items. The items are rated on a 4-point Likert-type scale ranging from 0 (Do not agree) to 3 (Totally agree). The total score ranges from 0 to 27 with higher scores representing a higher degree of positive mental health.

The Peer Mental Health Stigmatization Scale (PMHSS) (McKeague et al., 2015) will be used to assess stigmatizing attitudes towards children with mental health. The questionnaire comprises 11 items rated on a 5-point Likert scale ranging from 1 (strongly agree) to 5 (strongly disagree).The total stigma score is calculated by summing responses across all items. The resulting scores range from 11 to 55, whereby a lower score indicates a higher level of stigmatization.

The General Help-Seeking Questionnaire will be administered to assess the intentional help-seeking. Parents rate 8 items using a 7-point Likert scale (Extremely unlikely-Extremely likely). The questionnaire lists 8 potential sources of help options and an open-ended response to specify other persons not listed. For scoring purposes, the sum is used to calculate an overall score between 8 and 56. Higher scores indicate greater help-seeking intentions. The Actual Help-Seeking Questionnaire will be used to assess actual help-seeking behavior. Parents will be asked to tick resources from a provided checklist of 8 potential resources from whom they have sought help in the past six months because their child experienced a mental health problem. In addition, they will have the option to add a person not listed, to indicate that they did not seek help from anyone, and to indicate that they did not have a mental health problem in the past six months.

The Parental Stress Scale will be employed to assess parents' current levels of perceived stress in their caregiving role. The scale consists of 10 self-report items that are rated on a 5-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). The total score is calculated by summing all item responses, with higher scores indicating greater levels of parental stress.

The Brief Parental Self-Efficacy Scale will be used to assess parents' perceived self-efficacy in managing disruptive child behavior. This self-report questionnaire consists of five items rated on a 5-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). The total score ranges from 5 to 25, with higher scores indicating greater parental self-efficacy.

The Parenting and Family Adjustment Scales will be used to assess parenting practices and family adjustment. The PAFAS consists of 30 self-report items. It has two major subscales, the "Parenting practices" (18 items) subscale and the "Family adjustment" (12 items) subscale. The major subscales are further subdivided into minor subscales. All items are scored on a 4-point Likert scale ranging from 0 = "not at all (true)" to 3 = "very much (true)". The total score ranges from 0 to 90 and is calculated by summing the item responses. Higher overall scores indicate higher difficulty coping with the emotional demands of parenting, a strained child-parent relationship and greater use of coercive parenting techniques.

The Teachers' Sense of Self-Efficacy Scale-Short Version (TSES) version will be used to assess teachers' beliefs in their ability to influence student engagement, implement effective instructional practices, and manage classroom environment. The scale consists of 12 items, measuring three dimensions of self-efficacy: classroom management, instruction, and student engagement. Items are rated on a 4-point Likert scale ranging from 1 (not at all) to 4 (a lot). The overall self-efficacy score is calculated as the mean of the valid item responses.

The My Class Inventory - Short Form for Teachers (TMCI-SF) will be used to assess teachers' perceptions of classroom climate across five domains: Satisfaction, Friction, Competitiveness, Difficulty, and Peer Relations, as well as the perceived impact of the school counselor. The instrument consists of 24 items rated on a 5-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). Higher scores indicate more favorable perceptions in the domains of Satisfaction, Peer Relations, and School Counselor Impact, whereas lower scores are desirable in the domains of Friction, Competitiveness, and Difficulty. Total and subscale scores are computed by summing up the respective item responses.

The Peer Mental Health Stigmatization Scale (PMHSS) will be used to assess stigmatizing attitudes towards children with mental health. The questionnaire comprises 11 items rated on a 5-point Likert scale ranging from 1 (strongly agree) to 5 (strongly disagree).The total stigma score is calculated by summing responses across all items. The resulting scores range from 11 to 55, whereby a lower score indicates a higher level of stigmatization.

Description: The Children's Mental Health knowledge questionnaire is a self-constructed questionnaire comprising 16 items. It will be used to assess the gain of knowledge on mental health and help-seeking related to the content taught in the universal prevention programm. stigmatizing attitudes towards children with mental health. The questionnaire comprises 17 items that can be answered with either "True", "False" or "I don't know". "I don't know"-type responses are coded as "False".

Bias in mentalization, i.e. an overly negative, balanced or overly positive judgment of peer-interactions, will be assessed using an adapted version of the Biased Mentalization Task (Sharp et al., 2007). The adapted version was approved by the authors of the original publication. The Biased Mentalization Task measures biases in mentalizing through the use of 10 ambiguous peer-related social scenarios. The children can choose from three response options: One response option that contains an overly positive bias, one response option that contains an overly negative bias and a balanced response option. Each scenario will be displayed as a video. Frequency analyses and latent class analyses will be used to divide the children into the three bias types.

The Emotion Regulation Questionnaire for Children and Adolescents (ERQ-CA) will be used to assess the use of two emotion regulation strategies - cognitive reappraisal and expressive suppression. The scale consists of 10 items answered on a 5-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). Subscale scores are calculated as the mean of the valid items.

The Emotional Word-Emotional Face Stroop (EWEFS) task assesses attentional processes in children by measuring cognitive control over emotionally distracting stimuli and concurrently indexing processing speed and attentional vigilance via performance on congruent trials. On each trial, participants classify the emotional valence of a centrally presented word (positive or negative) via button press while ignoring a task-irrelevant face displaying either congruent or incongruent emotion. The task comprises 96 trials split into two 48-trial blocks: a mostly congruent block (75% congruent, 25% incongruent) and an equal block (50 % congruent, 50 % incongruent). Reaction time (RT) and accuracy on congruent trials capture basic processing speed and attentional vigilance.

The Parental Reflective Functioning Questionnaire Adolescent version (PRFQ-A) will be used to assess parental reflective functioning, i.e. a parent's capacity to understand and interpret both their own and their child's mental states. The PRFQ-A consists of 18 self-report items, divided into three subscales: Pre-Mentalizing Modes (PM), Certainty about Mental States (CMS), and Interest and Curiosity (IC). Items are rated on a 7-point Likert-scale ranging from 1= "Strongly disagree" to 7=" Strongly agree". Subscale scores are calculated as the mean of the respective items of each respective subscale. Higher scores on the PM subscale indicate greater difficulties in mentalizing, whereas higher scores on the CMS and IC subscales reflect greater certainty and curiosity about the child's mental states, respectively. It should be noted that a very high score on the CMS or IC subscale may indicate hyper/pseudo-mentalizing.

The Emotion Regulation Questionnaire (ERQ) will be used to assess the use of two emotion regulation strategies - cognitive reappraisal and expressive suppression - in parents. The scale consists of 10 items answered on a 7-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). Subscale scores are calculated as the mean of the valid items.

Parental adverse childhood experiences will be measured using the ACE-Q. The tool consists of a checklist of 10 adverse childhood experiences that cover neglect, emotional, physical, sexual abuse experienced as a child as well as drug problems, mental illness or incarceration of caregivers. Parents will be asked to answer the questions based on their own experiences up to the age of 18 years. Each checked item adds a score of 1. Vulnerability for a decrease in well-being correlates with higher ACE-Q scores, however a score above 4 is considered a particularly high risk.

The Levels of Personality Functioning Scale-Brief Form will be used to assess self-reported personality dysfunction based on the DSM-5 Alternative Model for Personality Disorders. The LPFS-BF consists of 12 items and is divided into two 6-item subscales: Self-Functioning and Interpersonal Functioning. Items are rated using a binary response format: 0 (No) or 1 (Yes). Scores are summed for each subscale and for the total scale, with higher scores indicating greater impairment in personality functioning.

The Multidimensional Scale of Perceived Social Support (MSPSS) will be used to assess self-reported social support in parents. The 12 items relate to support from family, friends and significant other and are rated on a 7-point Likert scale ranging from 1 (Very Strongly Disagree) to 7 (Very Strongly Agree). A total mean 1 to 2.9 is considered "low support".

Parents will be asked how many members live in their household and what their monthly household income is after social transfers (net) (i.e., net of government benefits and taxes) in Euros.

To identify households at risk of poverty, this study will use the EU-SILC (European Union Statistics on Income and Living Conditions) definition of poverty risk, as applied within each respective country (Eurostat, 2022). The at-risk-of-poverty threshold is defined as 60% of the national median equivalized disposable income after social transfers, adjusted for household size and composition using the modified OECD equivalence scale.

Parents will be asked to choose the most applicable of eight levels of education options ranging from "left school without degree" to "university degree". In addition, parents will have the option to add a level of education that was not listed or tick "other" as an option.

The official definition of the Federal Statistical Office of Germany will be used to collect data on participants' migration background. Children, parents and teachers will be asked three binary (yes/no) questions about their own place of birth as well as the place of birth of their parents. Additionally, parents attending without the other parent of the child will be asked to provide details about the other parent's place of birth.

Children's general cognitive ability will be assessed using the shortened 15-item version of the Raven's Standard Progressive Matrices (RSPM; Raven, 1989), adapted specifically for children and adolescents. The shortened RSPM strongly predicts the full 60-item RSPM scores (r = .89 for ages 9-12).

The test has one practice item where participants receive feedback. The 15 test items do not contain feedback.

Each participant's total score on the 15-item version is calculated by summing the number of correct answers, resulting in a raw score ranging from 0 to 15. This raw score serves as a proxy measure of general cognitive ability, however, it cannot be used for diagnostic purposes. Norm references do not exist but will be calculated within the FLOW-study.

The Children's Social Desirability Short Scale (CSD-S) will be used to measure social desirability bias in children (Miller et al., 2015). The scale consists of 14 binary (yes/no) items. An example item is: "Do you always listen to your parents?". The total score ranges from 0 to 14, with higher scores indicating greater social desirability bias. The internal consistency of the instrument is good (Cronbach's α = .83).