Conduct problems, schoolwork difficulties, and being bullied : A follow-up among Finnish adolescents

Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=usep20 International Journal of School & Educational Psychology ISSN: 2168-3603 (Print) 2168-3611 (Online) Journal homepage: https://www.tandfonline.com/loi/usep20 Conduct problems, schoolwork difficulties, and being bullied: A follow-up among Finnish adolescents Jaana Minkkinen, Risto Hotulainen, Jaana M. Kinnunen & Arja Rimpelä To cite this article: Jaana Minkkinen, Risto Hotulainen, Jaana M. Kinnunen & Arja Rimpelä (2018): Conduct problems, schoolwork difficulties, and being bullied: A follow-up among Finnish adolescents, International Journal of School & Educational Psychology, DOI: 10.1080/21683603.2018.1551819 To link to this article: https://doi.org/10.1080/21683603.2018.1551819 © 2018 International School Psychology Association Published online: 20 Dec 2018. Submit your article to this journal Article views: 207 View Crossmark data Conduct problems, schoolwork difficulties, and being bullied: A follow-up among Finnish adolescents Jaana Minkkinen a , Risto Hotulainen b , Jaana M. Kinnunen c , and Arja Rimpelä c,d a Faculty of Social Sciences (psychology), University of Tampere, Tampere, Finland; b Department of Teacher Education, University of Helsinki, Helsinki, Finland; c Faculty of Social Sciences (health sciences), University of Tampere, Tampere, Finland; d Department of Adolescent Psychiatry, Tampere, University Hospital, Pitkäniemi Hospital, Tampere, Finland ABSTRACT Continual conduct problems from adolescence to adulthood comprise a societal concern. Knowledge of school-related triggers and contributors to persistent conduct problems is important but still limited. We explored the role of schoolwork difficulties and being bullied by peers at school in the development of conduct problems, controlling for vulnerability factors of low cognitive competence and low prosociality. The data covered two measuring points on a longitudinal cohort of Finnish students between the ages of 16 and 18 (N= 5,108). All measures were self-reported. The regression and moderation modeling were executed using Bayesian estimation. Among 18-year-old adolescents, 14% of conduct problems were explained by conduct problems at the age of 16. Schoolwork difficulties had a direct positive effect on later conduct problems. Being bullied moderated effects of low cognitive competence and earlier conduct problems on later conduct problems. The findings show that we should also focus on school when risk factors for continuity of adolescents’conduct problems are sought out. KEYWORDS conduct problems; adolescence; schoolwork difficulties; bullying; cognitive competence; longitudinal study Increasing conduct problems, that is, antisocial and defiant activities, during adolescence comprise a societal concern, as some adolescents with antisocial behavior maintain their repetitive behavioral patterns into adulthood, thus facing ever-growing troubles in their adjustment to society. Adolescents who exhibit conduct problems in adolescence have a greater risk for multiple social and health impairments in later life (Colman et al., 2009; Khoddam, Jackson, & Leventhal, 2016). Moreover, conduct disorder in childhood and mid-adolescence predicts the tendency toward dropping out of school, drug use, and delinquency in adulthood (Breslau, Miller, Chung, & Schweitzer, 2011; Cerdá, Tracy, Sánchez, & Galea, 2011; Fergusson, Horwood, & Ridder, 2005; Heron et al., 2013; Moffit, Caspi, Harrington, & Milne, 2002; Mordre, Groholt, Kjelsberg, Sandstad, & Myhre, 2011; Sourander et al., 2005). Therefore, understanding contributors to the persistence of conduct problems throughout adolescence is important, but longitudinal research on the issue is still limited (Hankin, Abela, Auerbach, McWhinnie, & Steven, 2005). Specifically, little research has focused on the long-term risk factors in the school context, as most studies have focused on family or neighborhood settings. The present study explored the longitudinal associations of two school-related stress factors, schoolwork difficulties and being bullied by students at school, with conduct problems in Finnish adolescents between the ages of 16 and 18. The stress factors were studied alongside two vulnerability factors of conduct problems: low prosociality and low cognitive competence. Conduct problems in adolescence Conduct problems in adolescence include antisocial and defiant activities such as lying, stealing, physical aggression, disobedience, and coercive behaviors (Goodman, 2001). Conduct problems increase in middle adolescence, decrease toward young adulthood, and occur more commonly among boys than girls (Canino, Polanczyk, Bauermeister, Rohde, & Frick, 2010; Erskine et al., 2013). The increasing conduct problems have been explained, for example, by the developmental turbulence of the transitional period itself, especially among youth who exhibit conduct problems for the first time in adolescence (Barker & Maughan, 2009; Moffitt, 1993). In the transition from childhood to CONTACT Jaana Minkkinen [email protected] Faculty of Social Sciences (psychology), Tampere University, 33014 University of Tampere, Finland. Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/usep. INTERNATIONAL JOURNAL OF SCHOOL & EDUCATIONAL PSYCHOLOGY https://doi.org/10.1080/21683603.2018.1551819 © 2018 International School Psychology Association This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-ncnd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. adulthood, adolescents confront several biological, psychological, and social developmental tasks and challenges, including biological and sexual maturation, the development of personal identity, affirming independence and autonomy in the sociocultural environment, and the development of intimate sexual relationships (Christie & Viner, 2005; Harter, 2012). Due to these challenges, adolescents experience an increasing number of stressors and elevated emotional distress, which increase the probability of psychosocial problems (Ge, Conger, & Elder, 2001). Vulnerability factors for conduct problems Our theoretical framework is the stress-vulnerability perspective, which argues that risk for psychological problems is higher among adolescents who are more vulnerable and exposed to stressors (Grant, Compas, Thurm, McMahon, & Gipson, 2004; Grant & McMahon, 2005). The stress-vulnerability framework resembles the diathesis-stress model, which refers to genetic or biological vulnerabilities (Goforth, Pham, & Carlson, 2011) and has been used to explain, for example, the onset of depression or schizophrenia (Bandura, Pastorelli, Barbaranelli, & Caprara, 1999). Moreover, the stress-vulnerability perspective includes such characteristics and individual traits as vulnerability factors, which develop throughout adolescents’life experiences and make adolescents more prone to psychological problems, for example, antisocial behavior (Hankin et al., 2005). Drawing on evidence from earlier research, one of the most important vulnerability factors of conduct problems is low prosociality. Prosocial behavior is defined as voluntary social actions toward other people, such as being nice and kind, that are intended to help another individual or have positive consequences for others (Eisenberg & Mussen, 1989). Low prosociality refers to limited prosocial emotions and a lack of empathy and has been associated with conduct problems and antisocial behaviors (de Wied, Wied, & van Boxtel, 2010; Euler, Steinlin, & Stadler, 2017; Kimonis, Frick, & McMahon, 2014). The parallel findings have been discovered in longitudinal designs, for example, more concern for other people predicted less behavioral problems among 4to 10-year-old children (Hastings, Zahn-Waxler, Usher, Robinson, & Bridges, 2000). Moreover, peer ratings on low prosocial behavior at 8 years of age predicted criminal offenses by age 27, although early conduct problems were controlled for (Hämäläinen & Pulkkinen, 1996). Also, Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5) diagnostic criteria for conduct disorder include specifications due to limited prosocial emotions (American Psychiatric Association [APA], 2013). Considerable research has also detected that low cognitive competence is a vulnerability factor that exposes children to conduct problems (Kimonis et al., 2014). Longitudinal studies have shown that low intelligence and poor verbal ability are antecedents of later conduct problems and delinquency in adulthood (Farrington, 2003; Goodman, Simonoff, & Stevenson, 1995; Manninen et al., 2013). Furthermore, life-course persistent offending has been predicted by poor neuropsychological test scores (Moffitt, 1993; Piquero, 2001). Stressors in the school context We define stressors as environmental triggers that cause emotional distress and may prompt adolescents to behave antisocially in the presence of vulnerabilities (Grant et al., 2004; Grant & McMahon, 2005). So far, the majority of the studies on contextual risk factors of conduct problems have been carried out in family settings or high-risk neighborhoods (e.g., CooleyStrickland et al., 2009; Lorber & Slep, 2015; Murray & Farrington, 2010; Schonberg & Shaw, 2007; Trudeau, Mason, Randall, Spoth, & Ralston, 2012). Much less research has focused on stressors in the school context, although school is an important environment for children’s and adolescents’development. Considering the probable origins of stress in school, we suggest that schoolwork and social relationships are the most salient fields where an adolescent’s adverse experiences may cause notable stress (see Harter, 2012). Through formal and informal assessments at school, a poorly performing student frequently finds himself or herself to be worse compared to peers, which may evoke abundant feelings of loss, that is, loss of pleasure by competency and loss of the teacher’s and parents’appreciation. This causes emotional distress, which could lead vulnerable adolescents to behave antisocially according to the stress-vulnerability perspective (Grant et al., 2004; Grant & McMahon, 2005). Earlier research has found that poor grades and low school attainment are risk factors that predict later conduct problems and delinquency (Farrington, 2003; Hämäläinen & Pulkkinen, 1996; Moffit, Caspi, Dickson, Silva, & Stanton, 1996). Additionally, poor social relationships at school cause recurrent emotional distress, which has been shown to be a risk factor for many adolescents’psychosocial problems (Harter, 2012). Being bullied by peers at school has been associated with depressive symptoms (Hawker & Boulton, 2000) and with conduct problems. More conduct problems have been found among those 2J. MINKKINEN ET AL. adolescents who have been victims of bullying, for example, rejected by peers, and who have conflicted with their peers and teachers (Kasen, Johnson, & Cohen, 1990; Kumpulainen, Räsänen, & Puura, 2001; Laird, Jordan, Dodge, Pettit, & Bates, 2001; Lätsch, Raufelder, & Wulff, 2016; Schaeffer, Petras, Ialongo, Poduska, & Kellam, 2003). The present study Leaning on the stress-vulnerability perspective (Grant et al., 2004; Grant & McMahon, 2005), we suggest that the risk for conduct problems is higher for adolescents who are more vulnerable and are exposed to schoolrelated stressors. Drawing on the earlier evidence, we propose that difficulties in schoolwork and being bullied by peers are the most potential stressors for students at school (Farrington, 2003; Hämäläinen & Pulkkinen, 1996; Kasen et al., 1990; Kumpulainen et al., 2001; Laird et al., 2001; Lätsch et al., 2016; Schaeffer et al., 2003). Thus, our first purpose is to explore the direct effects of the difficulties in schoolwork and being bullied by peers on adolescents’conduct problems in the longitudinal design controlling for potential vulnerability factors. According to the literature, the most critical vulnerability factor of later conduct problems is earlier conduct problems (Canino et al., 2010; Costello, Mustillo, Erkanli, Keeler, & Angold, 2003; Erskine et al., 2013), but low prosociality and low cognitive competence have also been shown to have longitudinal effects on conduct problems (Farrington, 2003; Goodman et al., 1995; Hämäläinen & Pulkkinen, 1996; Hastings et al., 2000; Manninen et al., 2013; Moffitt, 1993; Piquero, 2001). Our second aim is to analyze the interaction effect of these three vulnerability factors and school-related stress factors (difficulties in schoolwork and being bullied by peers) on conduct problems. We propose two research questions: (a) To what extent do earlier difficulties in schoolwork and being bullied by peers predict later conduct problems when earlier conduct problems, vulnerability factors, and controlling variables are included in the analysis; and (b) to what extent do earlier difficulties in schoolwork and being bullied by peers moderate the effect of earlier conduct problems, low prosociality, and low cognitive competence on later conduct problems? The conceptual model of the moderation effects is displayed in Figure 1. Method Procedure and participants This study utilized longitudinal data collected in 2014 and 2016 in the Helsinki metropolitan area in a large MetloFin study (Hotulainen et al., 2016; Minkkinen et al., 2017). The baseline data of this study (T1) were collected at the end of compulsory school (ninth grade) from all comprehensive schools (N= 130) in the area. The students were reached via the participating schools: All students in the target grade were asked to participate. The educational authorities of each of the 14 municipalities gave permission for the study. Two online questionnaires, a Health Survey and a Learningto-Learn Assessment, were filled out in computer classrooms by 7,729 students (49.2% girls; 9.4% with an immigrant background), which was 53.6% of all the ninth graders in the area. The sample was not selected by gender compared with the official statistics in Figure 1. The conceptual model of moderation analyses. The stronger arrows refer to the hypothesized effects on conduct problems at T2. The thinner arrows refer to the correlation. The plus sign refers to the hypothesized positive association between variables. INTERNATIONAL JOURNAL OF SCHOOL & EDUCATIONAL PSYCHOLOGY 3 Finland. The average age of participants at T1 was 16 years (M= 15.91, SD = .38). The students were asked to complete the questionnaires during a typical double lesson (90 min) in the presence of a teacher. Teachers informed the students, and every student had a personal code to use in answering the questionnaire. Participation in the study was voluntary, which was mentioned at the beginning of the questionnaire on the first page. Participants over 15 years old are able to decide whether to participate without parents’allowance according to the National Advisory Board on Research Ethics (2009). Questionnaires were submitted anonymously. The study protocol was approved by the Ethics Committee of the National Institute for Health and Welfare in Finland. All participants at T1 were in the target group at the follow-up (T2). Data collection at T2 followed the principles and structure of the baseline survey but included only one combined questionnaire, and the data collection was extended to the institutions of upper secondary education in which the adolescent from the original cohort studied, that is, general upper secondary schools and vocational upper secondary schools. The final study population consisted of 5,108 adolescents (52.5% girls; 9.1% immigrant background) who had data of conduct problems at T2. The participants were aged 18 years at T2 (M= 17.91, SD = .36); 75.7% of them were students in general upper secondary schools, and 24.3% were students in vocational upper secondary schools. The adolescents who participated in the follow-up studied more often in general upper secondary schools (75.7%) than the official statistics showed (61%) in the study area and correspondingly less often in vocational upper secondary schools (Official Statistics of Finland, 2017). Attrition and nonresponse analysis There were several reasons for the nonresponses, one of which was students’absences from the class on the survey day (e.g., school absence, student in special needs education; about 10–15% of the students). The information about whether the student had refused to participate or was absent from school was not available from participating schools. Two separate questionnaires decreased the response rate at T1. Special schools and classes for children with serious learning difficulties, intellectual disabilities, or those situated in pediatric hospital wards were excluded from the sample because of the students’expected difficulty in answering the questions. Two administratively independent schools were not interested in participating in T1. To assess whether adolescents in the longitudinal sample shared characteristics with those who participated in the baseline survey, t-tests and chisquare tests were conducted. The longitudinal sample included more girls (52.5% versus 49.2%, χ2[1] = 3.931, p< . 001), more students with highly educated parents (41.2% versus 36.9%, χ2[1] = 13.571, p< .001), and less students who had been bullied at T1 than the baseline sample at T1 (M L = 1.22, M B = 1.25, t= 2.465, df = 6863.254, p< .001). No differences were found with regard to immigrant background. The longitudinal sample (M L ) included adolescents who had fewer conduct problems and schoolwork difficulties at T1 than the baseline sample (M B ) (respectively, M L = 1.149, M B = 1.299, t= 4.633, df = 6786.172, p< .001; M L = 6.301, M B = 6.901, t= 5.093, df = 10,147, p< .001). Also, the longitudinal sample included adolescents who had more prosociality and cognitive competence at T1 than the baseline sample (M L = 7.070, M B = 6.940, t=−2.894, df = 10,863, p< .01; M L = 50.516, M B = 44.683, t=−10.935, df = 11,277, p< .001). Some reasons for the differences between samples can be considered. Students who did not receive a place in further education after compulsory school are missing at T2 (5.3% of the T1 sample). Attrition bias was also caused by students in the cohort dropping out of further data collection because reaching the students in the institutions of upper secondary education was challenging at T2, and all schools were not willing to participate. Measures Conduct problems at T1 and T2 Conduct problems were self-assessed by students using asubscale of the Strengths and Difficulties Questionnaire (SDQ; Goodman, Meltzer, & Bailey, 1998). The SDQ is a widely used indicator of psychosocial adjustment among children and adolescents (Goodman, 2001; Koskelainen, Sourander, & Vauras, 2001). The SDQ covers subscales of conduct problems, peer relationship problems, prosocial behaviors, hyperactivity and inattention, and emotional symptoms, thus providing opportunities to screen the subscales separately, but the adolescents’total difficulties were also of interest in the collection of MetloFin data used in this study (Goodman, 2001; Hotulainen et al., 2016). Each subscale consists of five items, and for each item, the options include a three-point scale (0 = not true, 1 = somewhat true, 2 = certainly true; Goodman et al., 1998). The scale of conduct problems in the SDQ is composed of items related to lying, fighting, stealing, disobedience, and temper tantrums (Goodman, 2001). The reliability and validity of the SDQ have also been shown 4J. MINKKINEN ET AL. to be high in Finnish studies (Goodman, 2001; Koskelainen, 2008; Koskelainen et al., 2001). However, we had to drop the item concerning disobedience (“I usually do as I am told”), as the alpha reliabilities of conduct problems were undesirable according to the criteria of DeVellis (2003) if all five items were included (α T1 = .620, α T2 = .614). Thus, the item ratings of four items (lying, fighting, stealing, and temper tantrums) were summed up to a total score, with lower scores indicating fewer conduct problems (range 0–8). The alpha reliabilities were low but acceptable for both time points (α T1 = .684, α T2 = .696). The variables of conduct problems were highly skewed (M T1 = 1.149, SD T1 = 1.522, skewness T1 = 1.742, kurtosis T1 = 3.439; M T2 = .995, SD T2 = 1.446, skewness T2 = 1.845, kurtosis T2 = 3.850). Schoolwork difficulties at T1 Schoolwork difficulties were measured using an eightitem indicator that was used in the Finnish School Health Promotion studies (Luopa, Kivimäki, & Matikka, 2014). The question was “How are you doing at school? Do you have difficulties in the following areas: Paying attention to the teacher during class; Working in groups; Doing homework or similar tasks; Preparing for exams; Finding the right study-method for you; Doing assignments that require you to work independently; Doing assignments that require writing; and Doing assignments that require reading (e.g., a book)?”The options were on a four-point scale (0 = No, 1 = Some, 2 = Quite a lot, 3 = Very much). The results of the exploratory factor analysis using SPSS 23 demonstrated that the items were loaded on one factor. The explained variance of the factor was 69.382% (Eigenvalue 5.551; principal axis factoring with Oblimin rotation). Communalities were at least .568 for all items, and the highest factor loadings after extraction were on “Doing homework or similar tasks” and “Doing assignments that require writing”(both .689; KMO = .944; Bartlett’s Test χ2 = 21,504.835, df = 28, p< .001). The reliability analysis indicated good psychometric support for the internal consistency of the composition variable of schoolwork difficulties (α= .918). Thus, eight items were combined to form a composite variable, with a higher value indicating more difficulties (range 0‒24; M= 6.301, SD = 5.371, skewness = .836, kurtosis = .458). Being bullied by peers at T1 Bullying was defined in the questionnaire: “Bullying refers to intentionally and repeatedly hurting feelings of some student who has difficulties in defending him/herself. Bullying refers also to teasing a student repeatedly in a mean and insulting way. Bullying does not refer to teasing in a friendly and playful way. An argument or a fight between two roughly equal students is also not considered bullying.”Being a victim of bullying by peers at school was measured using one item that was used in the Finnish School Health Promotion studies (Luopa et al., 2014). The question was, “How often has a student/students bullied you at your school?”The options include a five-point scale (0 = never, 1 = I have been bullied less often than once a week, 2 = about once a week, 3 = several times a week, 4 = almost daily). At the age of 16 years, 8.1% of students had been bullied less often than once a week, 2.0% about once a week, 0.9% several times a week, and 1.7% almost daily. Prosociality at T1 Prosociality was measured using the SDQ’sprosociality scale. The scale comprises the five items related to sympathy, including kindness, sharing, helping, consideration for others, and volunteering (Goodman et al., 1998). For each item, the options include a three-point scale (0 = not true, 1 = somewhat true, 2 = certainly true). Item ratings were added together to obtain a total score, with lower scores indicating a lack of prosociality (range 0–10; M= 7.070, SD = 2.067, skewness = −.798, kurtosis = .870). The internal reliability was adequate (α= .712). Cognitive competence at T1 Cognitive competence was constructed by two cognitive tasks, Control of Variables and Invented Mathematical Concepts, with each measure reasoning in different domains taken from the Finnish Learningto-Learn Assessment (Kupiainen, Vainikainen, Marjanen, & Hautamäki, 2014). The Control of Variables task is based on a modified version of Shayer’s(1979) Science Reasoning Tasks, the Pendulum (Kupiainen et al., 2014). The task consisted of eight items, each including a comparison pair of variables in the world of Formula 1 races: driver, car, tires, and track. One item included three or four subsections, and in each one, the adolescents had to decide whether the comparison pair gave information to decide the single effect of the driver, car, tires, or track to the lap time. The options in each subsection were “No,”“Maybe,”and “Yes.”All the subsections had to be answered correctly to get points from the item. The task score was the percentage of correctly answered items (1 item = 12.50, 2 items = 25.00 etc.). The maximum score for the task was 100. Internal reliability was adequate (α= .822). INTERNATIONAL JOURNAL OF SCHOOL & EDUCATIONAL PSYCHOLOGY 5 The Invented Mathematical Concepts task was a modified version of the Sternberg Triarchic Test, Creative Number Scale (Sternberg, Castejon, Prieto, Hautamäki, & Grigorenko, 2001). In the task, two imaginary mathematical concepts were introduced to adolescents who should solve seven arithmetic tasks (items) based on the new concepts. There were four multiplechoice alternatives in each item. The score was the percentage of correct answers (1 correct answer = 14.29, 2 correct answers = 28.57 etc.). The maximum score for the task was 100. Internal reliability was adequate (α= .776). Cognitive competence was constructed by the mean of the two cognitive tasks divided by 10 (range 0‒10; M= 5.052, SD = 2.701, skewness = −.183, kurtosis = −1.154). Controlling variables The controlling variables were gender (boy = 0, girl = 1), age at T2 (range 16.7‒25; M= 17.911, SD = .359), immigrant background, and parents’education, which were all reported by students except the age, which was acquired from schools. Immigrant status was opted for the adolescentiftheadolescentoratleastoneoftheadolescent’s parents was born in a country other than Finland. The questions included the following: “In which country were your parents born?”(askedseparatelyformotherand father) and “Where were you born?”(the options were “in Finland”and “in another country”). Finland was coded as 0 and the other country as 1. Parents’education was assessed separately for mothers and fathers, and the highest level of either parent’seducationwasincludedin the analysis. The question was, “What kind of education do your parents have?”The options included the following: basic education only, vocational upper secondary education or vocational college, matriculation examination certificate and vocational college, university degree, and no mother or father. University degree was encoded as 1 and other options as 0. No mother or father was coded as a missing value. A total of 41.2% of students had at least one parent with a university-level education. This matches well with the official statistics concerning the education level in the population of the Helsinki Metropolitan area. In the area, 38–48% of all 25to 64-year-olds had university-level education (Jaakola, Cantell, & Vass, 2015). Data analysis First, we calculated intraclass correlation and design effect for the dependent variable as students were nested within schools. The intraclass correlation coefficient was .008, and the design effect was 1.29, which was below the suggested cutoff point of 2.0 (Hox & Maas, 2002). Thus, it was deemed unnecessary to take clustering of data into account, and we used the whole data set in the analyses. Linear regression analysis (Model 1) was accomplished in order to explore the longitudinal effects of schoolwork difficulties at T1 and being bullied by peers at school at T1 on conduct problems at T2. Model 1 included also conduct problems at T1, vulnerability factors at T1, and controlling variables. Several moderation models were executed to explore the interaction effects of the measures (research question b), and the significant interactions (Model 2–4) were further examined using regression plots. Multivariate linear regression and moderation analyses were conducted using the Mplus statistical package (version 8) with 30,000 iterations (Muthén & Muthén, 2012). As the outcome variable of conduct problems at T2 was not normally distributed, we applied the approach with Bayesian inference with no distributional assumptions because it was more appropriate, as opposed to traditional frequentist statistics (Muthén & Asparouhov, 2012). The Bayesian estimation with Markov chain Monte Carlo (MCMC) was executed with the potential scalereduction convergence criterion. One-tailed significance testing for posterior estimates at the criterion level of p= .025 was applied. The Bayesian information criterion and the Bayesian posterior predictive checking using χ2 were reported. Missing data in predictive variables (0–38.3%) were handled using full information maximum likelihood (FIML) estimation in Mplus. Descriptive statistics, statistical tests, and bivariate correlations were performed in IBM SPSS statistics 23. Results Conduct problems significantly decreased from T1 measurement to T2 measurement (Related-Samples Wilcoxon Signed Rank Test; Z=−7.499, p< .001, rank correlation = .401). There was moderate stability of conduct problems between the time points (Spearman’sρ= .397, p< .001). The longitudinal regression analysis showed that 14% of conduct problems measured at T2 were explained by the T1 measurement. Conduct problems, schoolwork difficulties, prosociality, and cognitive competence correlated significantly at T1 (all p< .001; Table 1). Direct effects The results of Model 1 showed that more schoolwork difficulties at T1 predicted more conduct problems at T2 when several other variables were controlled for, including the autoregression coefficient of conduct problems (Table 2). Using the confidence intervals of standardized regression coefficients, we compared the effects of 6J. MINKKINEN ET AL. schoolwork difficulties and the autoregression of conduct problems with each other. They were interpreted as significantly different because the confidence intervals did not overlap. That is, the effect of schoolwork difficulties at T1 was significantly smaller (b* =.086,95%CI: .050, .134, p< .001) than the effect of conduct problems at T1 (b* = .294, 95% CI: .254, .332, p< .001). Being bullied by peers at school at T1 did not predict conduct problems at T2 (p= .075). Lower prosociality and lower cognitive competence at T1 predicted more conduct problems at T2 (both p< .001). Although boys had more conduct problems than girls in the data, gender did not predict conduct problems at T2 in the multivariate regression analysis. Also, the age, immigrant background, and parents’education had no effects on conduct problems at T2. For Model 1, the R-square of conduct problems at T2 was 17.5%, meaning that 3.3% of the variance was explained by other variables than conductproblemsatT1. Moderation effects Firstly, we applied four moderation regression models to examine the pattern in which the stressor moderates the effect of the vulnerability factor on conduct problems. Each model included one stressor measured at T1 (school difficulties or being bullied by a student at school), one vulnerability factor measured at T1 (prosociality or cognitive competence), and their interaction term as predictors of conduct problems at T2. No significant interactions were found. Secondly, we ran two interaction models to examine whether the schoolrelated stressors (schoolwork difficulties or being bullied) moderate the effect of conduct problems at T1 on conduct problems at T2. Both models showed the significant interaction. Schoolwork difficulties at T1 moderated the effect of conduct problems at T1 on conduct problems at T2 (interaction term b* =−.077, p< .001; Model 2, Table 3). More conduct problems at T2 were found among those adolescents who had plenty of difficulties in schoolwork at T1 (the regression slope ain Figure 2), when compared to those who had fewer difficulties at T1 (slope b), except when the level of conduct problems at T1 was ca 1.2 SD above mean or higher (line c). Also, being bullied by peers at school at T1 exaggerated the autoregressive effect of conduct problems (interaction term b* =−.095, p< .001; Model 3, Table 3). More victimization at T1 predicted more conduct problems at T2 (the regression slope ain Figure 3) compared to less-victimized adolescents (slope b), except when the level of conduct problems at T1 was high, that is, ca .90 SD above mean or higher (line c). Table 1. Bivariate correlations 1 for continuous study variables. Variable 12345 1. Conduct problems T2 1 2. Conduct problems T1 .397*** 1 3. Schoolwork difficulties T1 .245*** .353*** 1 4. Being bullied T1 .113*** .194*** .156*** 1 4. Prosociality T1 −.145*** −.171*** −.154*** −.045* 1 5. Cognitive competence T1 −.173*** −.247*** −.235*** −.112*** .131*** Note. 1 Spearman ρ. *p< .05, ** p< .01, *** p< .001, two-tailed. Table 2. Predicting conduct problems at T2 (N= 5,108). 95% CI Predictor bSDb*SDLLUL Conduct problems T1 .276*** .018 .294*** .019 .254 .332 Schoolwork difficulties T1 .023*** .005 .086*** .021 .050 .134 Being bullied T1 .044 .035 .021 .017 −.007 .056 Prosociality T1 −.080*** .012 −.117*** .017 −.150 −.083 Cognitive competence T1 −.033*** .009 −.062*** .016 −.094 −.030 Girl −.003 .042 −.001 .015 −.029 .027 Age .047 .054 .012 .013 −.011 .039 Immigrant background .123 .069 .024 .014 −.001 .053 Parents’education −.071 .041 −.024 .014 −.053 .003 R 2 .173 nof free parameters 65 χ2 .500 BIC 108,316.084 Note. b = unstandardized posterior coefficient; SD = posterior standard deviation; b* = standardized posterior coefficient; CI = confidence interval; LL = lower limit; UL = upper limit; χ2 = Bayesian posterior predictive pvalue; BIC = Bayesian information criterion. *** p< .001, one-tailed. INTERNATIONAL JOURNAL OF SCHOOL & EDUCATIONAL PSYCHOLOGY 7 Thirdly, we executed two interaction models to examine whether the vulnerabilities (low prosociality or low cognitive competence) moderate the effect of conduct problems at T1 on conduct problems at T2. One significant interaction was found, as cognitive competence at T1 moderated the effect of conduct problems at T1 on Figure 2. Interaction of schoolwork difficulties and conduct problems at T1 predicting conduct problems at T2. Note: Regression slope aillustrates conduct problems at T2 with plenty of schoolwork difficulties at T1 (1 SD above mean). Regression slope billustrates conduct problems at T2 with not many schoolwork difficulties at T1 (1 SD below mean). Line cillustrates the highest level of conduct problems at T1 when the interaction is significant. Confidence intervals of 95% are displayed above and below the slopes. The figure includes standardized scales of the measures. Figure 3. Interaction of being bullied and conduct problems at T1 predicting conduct problems at T2. Note: Regression slope aillustrates conduct problems at T2 among adolescents who were bullied at T1. Regression slope billustrates conduct problems at T2 among adolescents who were not bullied at T1. Line cillustrates the highest level of conduct problems at T1 when the interaction is significant. Confidence intervals of 95% are displayed above and below the slopes. The figure includes standardized scales of the measures. Table 3. Moderation effects on conduct problems at T2. Model 2 Model 3 Model 4 Predictor b* SD b* SD b* SD Conduct problems T1 .346*** .019 .367*** .016 .360*** .017 Schoolwork difficulties T1 .124*** .018 Being bullied T1 .091*** .020 Cognitive competence T1 −.094*** .017 Interaction term −.077*** .019 −.095*** .020 .075*** .018 R 2 .146 .139 .141 nof free parameters 14 14 14 χ2 .465 .468 .489 BIC 35,838.443 39,133.709 35,059.491 Note. b* = standardized posterior coefficient; SD = posterior standard deviation; χ2 = Bayesian posterior predictive pvalue; BIC = Bayesian information criterion. *** p< .001 one-tailed. 8J. MINKKINEN ET AL.