1. Introduction
Worldwide, one in seven adolescents meet diagnostic criteria for mental health disorders, with depression, anxiety disorders, and behavioral problems being the most common [
1]. About 55% of adolescents experience mild to severe psychological symptoms at least once a week in Belgium [
2]. Furthermore, some researchers suggest that psychological symptoms, such as depressive and anxiety symptoms, have increased in adolescents compared to pre-pandemic estimates [
3,
4,
5]. This is worrying, as adolescent mental health symptoms have been linked to adverse long-term outcomes, such as failure to complete high school [
6], criminality [
7], and unemployment [
8] in adulthood.
Additionally, increasing rates of suicidal thoughts and behaviors in adolescents have been reported in numerous countries in the aftermath of the COVID-19 pandemic [
9]. Data from a Belgian sample report suicidal ideation in the past few weeks in 15% of adolescents (aged 15-25) [
10]. Numbers in Flanders (the Flemish-speaking part of Belgium) are comparable, with a lifetime prevalence for suicidal ideation of 22.3% for 11- to 18-year-olds [
11]. Although the last years brought a decreasing trend in suicide rates, Flanders has seen an increase in suicide in the group of 15-29-year-old females [
12]. According to a recent study from a Belgian sample, less than 50% of individuals who suffer suicidal ideation sought the help of a health professional in the past 12 months [
10]. There is a trend towards earlier onset of suicidal thoughts and behaviors [
13].
Similarly, a trend in earlier ages of onset for NSSI has been observed the past years [
13,
14]. Non-suicidal self-injury (NSSI) or the intentional and direct damage to one’s own bodily tissue without suicidal intent and without cultural aspects [
15] is a pressing concern in many educational settings around the world. Lifetime prevalence rates of NSSI in nonclinical adolescent samples range between 17-38% in several meta-analyses [
16,
17,
18]. A recent meta-analysis [
19] identified a trend towards more severe NSSI in the past decade. Furthermore, several studies underscore that adolescents start engaging at an increasingly younger age [
13]. Adolescents who began self-injuring at or before age 12 reported significantly more lifetime acts of NSSI, greater versatility of the method, and medically more severe NSSI than those who started NSSI around age 17 and older [
20]. Research has indicated that the expectation of future engagement in NSSI was predictive of NSSI recurrence [
21], subsequently influencing potential lethality and the variety of NSSI methods used [
22]. Furthermore, NSSI has been identified as a predictor of mental health disorders and suicidality in particular, especially when the behavior is engaged repetitively [
23,
24]. On the contrary, mental health problems are important risk factors for the development and maintenance of NSSI [
25,
26,
27]. A possible explanation for the association between mental health problems and NSSI behavior is the lack of adequate emotion regulation strategies [
28]. For example, te Brinke, et al. [
29] found that adolescents who reported both externalizing (e.g., rule-breaking, aggression) and internalizing problems (e.g., anxiety, depression) adopted a maladaptive regulation style, which in turn is a maintaining factor for NSSI [
26]. Furthermore, NSSI itself can be seen as a maladaptive regulation style [
30,
31]. By participating in NSSI, adolescents can find an alternative way to cope with distressing situations, alter their social environment, gain relief from negative emotions or thoughts, or change self-cognitions [
32].
Although mental health problems and NSSI are common among adolescents, only 17.5% of 16 to 18-year-olds seek professional help [
33]. This may be due to adolescents encountering stigmatic barriers when considering seeking help, such as negative beliefs about professional mental health care [
34], negative responses to disclosure [
35,
36], and lack of knowledge about where to seek help [
37]. Furthermore, more severe mental health problems, including NSSI and suicidality, lead to a greater delay in seeking help [
38]. For example, according a recent study from a Belgian sample, less than 50% of individuals who suffer suicidal ideation sought the help of a health professional in the past 12 months [
10]. Some factors identified to date that promote help-seeking behavior [
39] are mental health literacy [
40,
41] and appropriate responses to disclosure of mental health issues [
42,
43]. The prevalence rates, adverse long-term outcomes of mental health problems in adolescents and low rates of help-seeking behavior call for effective preventative and early interventions to decrease mental health complaints and NSSI in adolescents.
The school setting may be an opportune context to implement such preventative and early mental health interventions, as they can take place where adolescents spend a large portion of their time [
44] and reach a larger group of children who are potentially at risk for developing mental health problems or participating in NSSI [
45]. It also allows us to educate peers on mental health (mental health promotion (MHP)) and on responses to mental health issues, which in turn leads to less stigma and more help-seeking behavior [
46,
47,
48,
49].
Several meta-reviews over the past decades [
50,
51] found benefits of classroom-based preventative and mental health psychological interventions. One of the major benefits is that they target the entire student population at relatively low cost [
52]. Studies have also shown the promising effectiveness of universal school-based programs in promoting mental health and strengthening resilience while mitigating psychological problems among students. For adolescent student groups specifically, universal school-based prevention programs have been extensively researched to evaluate their effectiveness in improving academic success [
44,
53], addressing positive mental health outcomes, including building resilience, coping behavior and subjective well-being [
44,
54,
55,
56], or improving emotion regulation skills [
57], as well as addressing a range of mental health issues such as substance misuse [
58], suicidality [
59], and other mental health concerns [
60,
61,
62]. For example, the systematic review and meta-analysis of Tejada-Gallardo, et al. [
63] found evidence for the efficacy of school-based multicomponent positive psychology interventions in improving mental health in the short and long-term with small effect sizes ranges from g = 0.2 to g = 0.3 for subjective well-being, psychological well-being and depressive symptoms.
Notwithstanding the bulk of evidence concerning a variety of mental health outcomes, there are only 2 studies that focused on the effectivity of universal school-based programs with regard to NSSI. One such intervention is the so-called Peer Education Programme (NSSI-PEP) [
64], which targets four key risk factors for NSSI, namely pubertal change, body image, self-esteem, and emotion regulation, found positive changes in emotion regulation skills, self-esteem, and fear. Another intervention is the “HappylesPLUS” by Baetens, et al. [
65]. Baetens, Decruy, Vatandoost, Vanderhaegen and Kiekens [
65] investigated the outcomes of an in-class room universal mental health programme ’Happyles’ [
62] and compared it with the outcomes of an enriched program, with a one-hour NSSI-focused psycho-education module (’KRAS’). Both groups reported a reduced tendency for future NSSI and improved emotional awareness six weeks after the program completion, compared with the pre-test results. Qualitative analysis of the data suggested that “HappylesPlus” may provide direct benefits for students that actively engage in NSSI, such as a greater willingness to seek help for this behavior [
65].
Another shortcoming is that most existing prevention programmes either focus on positive mental health / positive psychology interventions [
63] or on interventions strengthening mental health literacy [
66]. However, when aiming to target the whole class population, it is best to build on a dual-continuum model of mental health [
67]. This model has as its premise that mental illness and positive mental health predict explain different outcomes (which indicates that these are two distinct constructs), while simultaneously these constructs share some degree of overlap. When measuring functioning on both constructs, four distinct ‘at-risk’ subgroups can be distinguished. This brings significant potential for intervention development [
68]. More specifically a so-called multi-tiered intervention, with three tiers (that are commonly called universal, selective, and indicated) can be adopted [
69]. However, more research on the effectivity of multitiered school-based interventions that focus on both the promotion of mental wellbeing and the prevention of mental health problems, and NSSI specifically, is needed.
The current study therefore aims to further contribute to the largely unexplored question of the effectiveness of multi-tiered school-based early interventions that both target universal resilience building and mental health literacy. Apart from the earlier work of Baetens, Decruy, Vatandoost, Vanderhaegen and Kiekens [
65] and Cipriano, Aprea, Bellone, Cotrufo and Cella [
64], there is an important gap in research to examine the effectiveness of school-based early intervention programs to prevent NSSI in schools. Since the initial pilot study by Baetens, Decruy, Vatandoost, Vanderhaegen and Kiekens [
65], the Flemish Institute for Healthy Living, a center of expertise for health promotion, has launched a guide model for mental health promotion (‘The Happiness Triangle’) and a related intervention for educational settings (‘Happiness in the classroom’). This intervention contains a psychoeducational package comparable to the ‘Happyles’ programme [
62] evaluated in the pilot study. However, ‘Happiness in the classroom’ as a whole, nor its separate elements, has not yet been quantitatively examined for effectiveness.
Therefore, the main purpose of this study is to investigate the effectiveness of a multi-tiered school intervention combining the Happiness Triangle psycho-educational package, with the KRAS psychoeducational module for NSSI, and subsequent tailored advice on an individual level [
65]. More specifically, the current study investigated whether the level of psychological symptoms (i.e., internalizing and externalizing symptoms) in young adolescents (11-14 years) is significantly reduced and the level of mental well-being significantly improved in students who followed the school-based early intervention programme compared to the control group. Additionally, we examine whether the program has an effect on reducing the likelihood to engage in NSSI and increases both help-seeking behavior and emotion regulation strategies compared to the control group.
In line with recent studies with Flemish adolescents in similar age ranges, we expect 50% to report psychological symptoms [
2] and 7% to report NSSI the past year [
70]. We expect an overall positive well-being for the majority of the group and no more than 20% to report low well-being [
2]. Furthermore, the majority of Flemish adolescents in the first grade are expected to have primarily adaptive emotion regulation strategies, with only a minority reporting difficulties in emotion regulation. Flemish adolescents are often not very interested in help-seeking behaviors for mental health problems.
Furthermore, based on previous studies on universal prevention programmes [
59,
65], we expect that a universal prevention programme (with a specific NSSI -focused module KRAS) has a positive effect on rates of internalizing and externalizing symptoms, and NSSI, and decreases in emotion regulation problems, and finally has a positive impact on help-seeking attitudes.
2. Materials and Methods
2.1. Participants
In total, 329 students from the early intervention group participated in the pre-measurement, 242 students in the post-measurement (26.4% dropouts), and finally 166 students in the follow-up measurement (50.8% dropouts). Overall, for 62 cases, the questionnaires could be linked to each other via a pseudo-anonymized code (53.2%, female, Mean age = 12.66, SD = 0.673, min. = 11, max. = 14) for the three timepoints (25.62%//18.9% of the total)).
Regarding the control group, 185 students completed the questionnaire in T1, 184 at T2 (0.54% dropouts) and 183 at T3 (1.08% dropouts), of which 101 cases could be linked for the 3 timepoints (54.89% of 185) (55%, female, M age = 12.16, SD = 0.518, min. = 11, max. = 14).
To have an equal sample size in both the early intervention and control groups, we randomly selected 62 cases from 101 participants in the control group. To ensure that there are no significant differences in the baseline characteristics of the participants who dropped out and the students who participated in the three assessments, we analyzed the variations between groups. Results indicated no significant differences in terms of mean age and gender between them (p>0.05) (see
Table 1 below).
2.2. Measures
Non-suicidal self-injury (NSSI). Participants received the Brief Non-Suicidal Self-Injury Assessment Tool (BNSSI-at) [
71]. Items regarding NSSI methods, functions, recency, frequency, age of onset, cessation, and probability of future engagement were enquired. The test-retest reliability and validity of the NSSI-AT is adequate [
72].
Emotion regulation. How students regulate their emotions was measured with the Difficulties in Emotion Regulation Scale (DERS-36) [
73]. The DERS-36 contains 36 items on a 5-point Likert scale (5 = almost never to 1 = almost always). In a sample of adolescents specifically, the subscales showed good to excellent internal consistency [
74]. In the current study, the internal consistency of the total score was excellent, with a Cronbach’s alpha of 0.87 at T1, 0.91 at T2, and 0.92 at T3. The internal consistency of the subscales was also in the acceptable to good range: Lack of Emotional Clarity (α= 0.76 at T1, 0.80 at T2, and 0.85 at T3), Difficulties Engaging in Goal-Directed Behavior Goals (α= 0.76 at T1, 0.84 at T2, and 0.86 at T3), Impulse Control Difficulties (α= 0.82 at T1, 0.83 at T2, and 0.82 at T3), Limited Access to Effective Emotion Regulation Strategies (α= 0.76 at T1, 0.84 at T2, and 0.79 at T3), and Non Acceptance of Emotional Responses (α= 0.69 at T1, 0.78 at T2, and 0.64 at T3).
Mental well-being. The Warwick-Edinburgh Mental Wellbeing Scales (WEMWS) [
75] were administered to gain insight into participants’ general mental well-being. It consists of 14 items with a 5-point Likert scale (0 = none of the time to 4 = all of the time). The sum of the item scores is calculated to obtain a total score. The internal consistency of the WEMWS in the current study was good (α= 0.90 at T1, 0.92 at T2, and 0.94 at T3).
Psychological symptoms. To track internalizing and externalizing symptoms, the brief self-report version of the Youth Outcome Questionnaire (Y-OQ-SR 30.2) [
76,
77] was used. The Y-OQ-SR 30.2 has 30 items on a 5-point Likert-type scale (0 = almost never or never to 4 = almost always or always), a score range of 0 to 120, and can be divided into six subscales: somatic, social isolation, aggression, conduct problems, hyperactivity/distractibility, and depression/anxiety. The higher the total score, the greater the distress experienced by the participant. For both the total score and the subscales, internal consistency and test-retest reliability were found to be adequate in a community youth sample [
77]. In the current study, Cronbach’s alpha for the total score was excellent (α= 0.91 at T1, 0.93 at T2, and T3). The internal consistency of the subscales Somatic Problems (α= 0.70 at T1, 0.75 at T2, and 0.77 at T3), Conduct Problems (α= 0.79 at T1, 0.80 at T2 and 0.78 at T3), and Depression/Anxiety (α= 0.81 at T1, 0.85 at T2, and 0.82 at T3) was good. The internal consistency of Social Isolation (α= 0.68 at T1, 0.70 at T2 and 0.68 at T3), Aggression (α= 0.71 at T1, 0.72 at T2, and 0.63 at T3), and Hyperactivity/Distractibility (α= 0.64 at T1, 0.68 at T2, and 0.69 at T3) was acceptable.
Depressive symptoms. The Centre for Epidemiologic Studies Depression Scale (CES-D) [
78] was administered to identify the presence and extent of depressive feelings or symptoms. The questionnaire consists of 20 items, which are answered on a 4-point Likert scale (0 = seldom or never (less than one day) to 3 = almost always or always (5-7 days)), and includes the following components: depressed mood, feelings of guilt and inferiority, feelings of helplessness and despair, loss of appetite, sleep disturbances and psychomotor delay. Cronbach’s alpha for the CES-D in the current study were good (α= 0.92 at T1, 0.84 at T2 and 0.85 at T3).
Help-seeking behavior. The help-seeking behavior of students was assessed using the Short Form Attitudes Toward Seeking Professional Psychological Help Scale (ATSPPHS-SF) [
79]. The ATSPPHS-SF is a unidimensional instrument with 10 items (e.g. ‘If I believed I was having a mental breakdown, my first inclination would be to get professional attention’) that are answered on a 5-point Likert scale (1 = completely disagree to 5 = agree completely) [
79]. Higher scores indicate more positive attitudes toward seeking professional help, which has been associated with greater willingness to engage in future help-seeking behavior and less stigma related to treatment. In several studies, adequate internal consistency and test-retest reliability have been found [
80]. Although these studies were conducted on college student samples, researchers concluded that no items were included that would be inapplicable or inappropriate in an adolescent sample [
81]. In the present study, Cronbach’s alpha for the total score was 0.64 at T1, 0.76 at T2, and 0.80 at T3.
2.3. Procedure
First, ethical approval was obtained from the Brussels UZ Medical Ethics Committee (BUN: 1432022000257). From January to May 2023, a universal psychoeducational package Happiness Triangle, as developed by the Vlaams Instituut Gezond Leven, was installed in the first and second grades of six secondary schools in Flanders by the prevention team of Vrij CLB Brabant Oost. The programme combines class-based universal prevention package focusing on resilience (including 3 classroom hours on well-being, resilience, coping, and help-seeking), a psychoeducational module on NSSI (KRAS module) [
65] and a tailored advice on an individual level. The programme and the brief counseling (15 min per student) were delivered by a team of 3 local school counselors (of vCLB Brabant Oost).
Before lessons, students and their parents received an information sheet and informed consent form their teacher. If both parents and students consented to participate, the students were asked to individually complete an pseudo-anonymous, online pre-, post-, and follow-up self-report questionnaire via a secure web survey platform (i.e. Qualtrics XM). The questionnaire enquired about demographics, NSSI and suicidality, emotion regulation, internalizing and externalizing symptoms, help-seeking behavior, and mental health stigma. The pre-questionnaire was completed before the first lesson, the post-questionnaire was completed immediately after the fourth lesson, and the follow-up questionnaire was completed one month after the post-questionnaire. All participating students were randomly assigned a ID code which they had to fill in at the beginning of each questionnaire. This allowed the researchers to link responses across time points without compromising student anonymity. In addition to the intervention group, a group of students who had not participated in the prevention classes were also asked to fill in the questionnaire at three time points, after receiving informed consent from both the students and their parents. These students, who were matched by age, region and educational level, served as the control group.
Each student was also given an open invitation to a brief 15-minute individual counselling session at school with a member of the school counselling team. During this session, students had the opportunity to express their questions and those who exhibited an elevated risk profile (e.g., increased psychological complaints and decreased mental well-being) were referred to professional support. Students with immediate risk (e.g., acute suicide risk) were referred to a crisis center and closely followed up by the school counselor center. Finally, incentives (i.e. movie tickets) were distributed to 50 randomly selected students and a brief overview of the study results was sent by email to students who requested it.
2.4. Data Analysis
Descriptive statistics for the final sample were reported for the study variables with means and standard deviations reported for the continuous variables (i.e., difficulties in emotion regulation, depressive symptoms, mental well-being, internalizing and externalizing problems, and help-seeking behavior) and sample distribution for the ordinal and nominal variables (i.e., prevalence of NSSI and suicide attempts). Furthermore, the differences between the intervention group and the control group were assessed at T1. Independent samples t-tests were performed to test for differences in the continuous variables, whereas chi-square tests were used to compare ordinal and nominal variables.
To evaluate the changes between pre, post, and follow-up measure, repeated measure ANOVAs were used for the continuous data. In these ANOVAs, a time factor was included, which entails running an omnibus test of differences across timepoints. Furthermore, an interaction term between time and group was included in order to assess whether the differences across time points differed between the experimental and control group. To get a more detailed insight, post hoc analyses were conducted. First, to assess within-group differences across timepoints in detail, separate ANOVAs in each group were conducted and contrasts were applied through the Bonferroni post hoc test to investigate pairwise differences between time points. Furthermore, the interaction effect between time and group was assessed in more detail by testing the differences scores between time points (i.e., pre vs post; post vs follow-up) between groups (i.e. intervention vs control group) using ANOVAs. Before performing repeated measures ANOVAs, the assumption of normality of the data was tested using the Kolmogorov-Smirnov test, which confirmed the normal distribution of most variables in both the intervention and control groups (p > .05). However, in both groups, depressive symptoms at all three-time points, internalizing and externalizing problems at T2 and T3, and help seeking behavior at T3, as well as the data for the internalizing/externalizing problems at T1 in the control group, were not normally distributed and were normalized using the fractional rank method. Additionally, the assumption of sphericity of the test statistics was tested using the Mauchly test of sphericity and the results were not significant (p > .05) for most variables, implying that the variances of the differences between all combinations of related groups (levels) are equal. In the case of significant differences between the variances, the Greenhouse-Geisser was applied.
Ordinal and nominal variables (i.e., suicide and NSSI prevalence) were analyzed using the nonparametric Mann-Whitney U test and the Wilcoxon signed rank test. Partial Omega Squared (ω2p) was calculated to determine effect sizes and interpreted as 0.01= small effects, 0.06= moderate effects, and 0.14= large effects. ω2p is a less biased version of partial eta-squared (η2p) for ANOVAs [
82]. All analyses were performed using SPSS (version 29) and statistical significance was determined with an alpha level of .05.
4. Discussion
The current study focuses on assessing the effectiveness of a multi-tiered early school-based intervention for strengthening mental well-being, emotion regulation skills, and help-seeking behaviors in adolescents on the one hand and preventing NSSI, and mental health problems in general, on the other. Given the increase in psychological symptoms and maladaptive behaviors (such as NSSI and suicidality) in young adolescents, this study addresses an important societal concern. It is the first study to examine the effectiveness of the universal school-based psycho-educational package developed by Vlaams Institution Gezond Leven, which is freely available for all Flemish schools. Furthermore, it is one of the first studies to explicitly examine the effectiveness of a multi-tiered school program in the prevention of NSSI.
In line with our hypothesis and post-COVID literature, the prevalence of psychological symptoms and maladaptive behaviors such as NSSI and SSI [
11,
83,
84], depression, and internalizing and externalizing problems [
3,
85,
86,
87] remain high, even in 2023. In the current sample, 40.3% of adolescents meet the clinical range for internalizing and externalizing symptoms. In total, 55.4% report psychological distress, approximately 50% exhibit depressive symptoms, 22% engage in NSSI, and 4.8% report a suicide attempt. The prevalence rates of NSSI and suicidality are higher than expected among these young adolescents (11-14 years old). In addition, the majority of adolescents (around 70%) reported negative attitudes for help-seeking. Flemish adolescents are in fact not keen on helping to solve mental health problems.
The Happiness Triangle in combination with the KRAS module showed promising results, where the intervention group after 4 classroom hours of early intervention showed a significant decrease in internalizing and externalizing symptoms, and more specifically depressive symptoms and frequency of NSSI. In addition, the adolescents in the intervention group showed significant improvements in emotion regulation skills and help-seeking behaviors compared to participants in the control group. The findings are consistent with previous research, supporting the mental health benefits of school-based programs in adolescents [
44,
54,
55,
56,
57,
58,
59,
60,
61,
62,
63,
88].
Notwithstanding the strengths of this study (e.g., multi-component program, naturalistic design) and robust findings in line with previous studies, there are several limitations which we would like to acknowledge as well. First, the response rates of 50% was rather low, which is often the case in naturalistic intervention studies. Although, we are not aware of a systematic bias, low response rates can threaten generalizability of the results to all students. Furthermore, it is essential to note that less than 30%, of the total sample could be linked through the pseudo-anonymized coding system. Despite this limitation, comparisons between on group level yielded similar results. Secondly, the lack of blinding in the allocation of participants to the intervention and control groups introduces the potential for bias, particularly considering that schools had autonomy in enrolling classes for the intervention study. While the prevalence of psychological symptoms and maladaptive coping behaviors persisted at levels consistent with those observed during the COVID-19 pandemic, it is imperative for future research to validate these findings and consider whether participating schools may be disproportionately affected by such issues and were therefore motivated to participate in this study. Furthermore, as this study evaluates the implementation of the programme to pre-adolescents ages 11-14, its generalizability to other age groups or students in vocational tracks is limited. Future research endeavors should prioritize the development of more interactive prevention programmes that cater to diverse demographics, including refugees and vocational track students. Finally, the collaboration with a local school counselor center facilitated program delivery and data administration; however, the absence of adherence to the programme records poses a notable limitation, despite the positive outcomes observed.
Notwithstanding these limitations, our study adds to our knowledge on the potential effectivity of school-based early interventions, and informs academia on the potential benefits of a multicomponent approach to the prevention of NSSI behaviors in early adolescence. With the high prevalence of psychological symptoms and maladaptive behaviors among school-aged populations, multi-component universal school prevention can counter the current pressure sensed in all inpatient and outpatient child and adolescent psychiatry services, which manifest in lengthy waiting lists and overwhelming burdens on existing resources. By demonstrating the efficacy of school-based prevention programs in improving mental well-being and reducing the incidence of NSSI, our findings offer a proactive approach to alleviating this burden. Implementing such interventions has the potential to not only mitigate the strain on mental health services but also to promote early intervention and support for students at risk, thereby fostering healthier outcomes and reducing the demand for specialized psychiatric care in the future. This relevance underscores the critical importance of integrating preventive measures within educational settings to address the growing mental health needs of young individuals.