We used data on resilience from 2,839 adolescents (mean age 13.93; 49.6% boys) from the Health Behaviour in School-aged Children (HBSC) study conducted in 2018 in Slovakia. These adolescents constituted a random sample of about 43.0% of all children participating in the HBSC study. We used three-step sampling to obtain a representative sample. In the first step, 140 larger and smaller elementary schools located in rural as well as in urban areas from all regions of Slovakia were asked to participate. These were randomly selected from a list of all eligible schools in Slovakia obtained from the Slovak Institute of Information and Prognosis for Education. The school response rate (RR) was 77.9%. Second, a random selection was taken from the resulting schools, leading to a representative sample of 8,405 adolescents, aged 11–15 years (mean age 13.43; 50.9% boys), from the fifth to ninth grades of the elementary schools; one class per grade was selected. Third, we obtained data on resilience from a random sample of the 13- to 15-year-olds among these adolescents, yielding 2,839 adolescents.

The study was approved by the Ethics Committee of the Medical Faculty at P. J. Safarik University in Kosice (16N/2017). Parents were informed about the study via the school administration and could opt out if they disagreed with their child’s participation. Participation in the study was fully voluntary and anonymous, with no explicit incentives provided for participation.

Emotional and behavioural problems (EBP) were measured with the Strengths and Difficulties Questionnaire [35], from which we used the 20 difficulty items. The response categories were: not true (0), somewhat true [1], and certainly true [2], leading to scores ranging from 0 to 40, with a higher score indicating more problems. The sum score for overall difficulties can range from 0 to 40 [36]. Cronbach’s alpha for whole scale was 0.73 in our sample.

Adverse childhood experiences (ACE) were measured with Adverse Childhood Experience Questionnaire, which includes 11 questions on events: “Have you ever experienced any of the following serious events?” (Death of a brother/sister, Death of your father/mother, Death of somebody else you love, Long or serious illness of yourself, Long or serious illness of one of your parents or of someone else close to you, Problems of one of your parents with alcohol or drugs, Repeated serious conflicts or physical fights between your parents, Separation/divorce of your parents, Separation of your parents due work abroad, Moving to another house/flat, or city/village, Transfer to another school) [2, 37]. The response categories were “Yes” and “No”. We counted the number of ACE experienced and used this as a continuous score.

Resilience was measured using the Child and Youth Resilience Measure (CYRM-12) Child Version, which includes 12 items [38, 39] for adolescents 13 years and older (7th, 8th and 9th grade). The CYRM-12 is a measure of the resources (individual, relational, community and cultural) available to individuals that may bolster their resilience. The response categories ranged on a 3-point scale (No/Sometimes/Yes), leading to scores ranging from 12 to 36, with a higher score indicating higher resilience. Cronbach’s alpha in our sample was 0.84.

The Family Affluence Scale III (FAS III) was used as a measure of socioeconomic status. It consists of six questions: “Does your family own a car, van or truck?” (Yes/Yes, one/Yes, two or more); “Do you have your own bedroom for yourself?” (Yes/No); “How many computers does your family own?” (None/One/Two/More than two); “How many bathrooms (room with a bath/shower or both) are in your home?” (None/One/Two/More than two); “Does your family have a dishwasher at home?” (Yes/No); “How many times did you and your family travel out of your country for a holiday/vacation last year?” (Not at all/Once/Twice/More than twice). We converted the FAS summary scores to a final score, with a normal distribution and a range from 0 to 1. We then created tertile categories of low (0–0.333), medium (0.334–0.666) and high (0.667–1) socioeconomic position [40].

First, we described the sample using descriptive statistics. Second, we assessed the associations of ACE with EBP and of resilience with EBP (Model 1). Third, we repeated this assessment with adjustments for gender, age and family affluence (Model 2). Fourth, we explored the change in the associations of ACE with EBP after adding resilience (Model 3) in order to explore the mediation by resilience. For the last three steps we used multivariate linear models performed on 5000 bootstrap samples adjusted for age, gender and family affluence. Finally, we performed mediation analysis using PROCESS macro model 4 [41] and controlled for age, gender and family affluence on 5000 bootstrap samples. The indirect effect was calculated using the a*b product method, and bootstrapped 95% confidence intervals (CI) were calculated. Statistical analyses were performed using SPSS v.20.

We assessed the crude associations of the number of ACE and resilience scores with the number of EBP (Table 2, Model 1). We found more ACE to increase the number of EBP (B = 0.78; 95% CI: 0.67|0.90) and more resilience to decrease it (−0.73; −0.79|−0.67). B represents unstandardized coefficients from linear regression models on 5000 bootstrap samples.

In the next step we assessed the associations of the numbers of ACE and EBP with adjustment for potential confounders (Model 2). Again, we found each additional ACE to increase the numbers of EBP (0.73; 0.62|0.83), also after the adjustment.

We then assessed the role of resilience as a mediator in the association of numbers of ACE and EBP with adjustment for potential confounders (Model 3). We found that adding resilience to the model (−0.69; −0.74|−0.64) weakens the association of ACE with EBP (to 0.47; 0.37|0.57), suggesting a mediation role of resilience. Next, we assessed the strength of the mediation role of resilience in the association between numbers of ACE and EBP using the a*b product method, with adjustment for potential confounders (Figure 1). The results suggested that resilience mediated the association of ACE with EBP with an indirect effect of ab = 0.25 (0.18|0.32).

The main strengths of our study are its large nationally representative sample and its use of the well-established HBSC methodology. This study also has some limitations. Our research had a cross-sectional design, which hinders conclusive inferences about causality. Furthermore, we used self-reported data from adolescents, which may lead to e.g., the underreporting of ACE. We used well-validated questionnaires for this, but we cannot exclude some underestimation of their occurrence. The third limitation of this study is that we used the ACEQ, which does not include questions about childhood abuse. This topic is evidently hard to measure based on questionnaires but could have even stronger effects than the ACE that we included. This means that we may have underestimated the real associations. The fourth limitation is that we did not assess whether the association and mediation as found is stronger for high levels of either the outcome (dependent) or of the determinant (independent). However, if limiting the range of determinant or outcome, then typically the association will weaken.

We found that resilience plays a mediating role among adolescents with ACE in the incidence of EBP. Our study suggests that it is important to help adolescents with ACE build and be able to use internal and external sources of resilience, as we know these sources can decrease the negative impact of ACE on EBP. Resilience may affect the association of ACE and EBP differently depending on the specific type of ACE. Future research could focus on specific ACE in relation to EBP; and on the role of resilience in relation to specific ACE and EBP. Our results imply that better communication between family and school, e.g., classroom teachers and school psychologists, could support external sources of resilience in adolescents with EBP. Future research could take a closer look at building resilience at a younger age, which may then prevent EBP in adolescents. A longitudinal study may be useful for examining the causality of these findings. Longitudinal research could shed more light on this topic for better understanding the building of resilience already in childhood.

Resilience plays an important role in the relationship between ACE and EBP. We found that resilience is a mediator in the association between ACE and EBP among adolescents.