Eur Child Adolesc Psychiatry DOI 10.1007/s00787-014-0524-0
ORIGINAL CONTRIBUTION
The relation between bullying and subclinical psychotic experiences and the influence of the bully climate of school classes Esther M. B. Horrevorts • Karin Monshouwer • Johanna T. W. Wigman • Wilma A. M. Vollebergh
Received: 13 May 2013 / Accepted: 27 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract This study aims to examine the association between the bully climate of school classes and the prevalence of subclinical psychotic experiences among students who are involved in bullying (either as bully or as victim). Data were derived from the Dutch health behavior in school-aged children survey of 2005, a nationally representative cross-sectional study with a total of 5,509 adolescents between the age of 12 and 16. The data were analyzed using a multilevel regression analysis. The study revealed that both bullying and being bullied in school classes was associated with an increased level of subclinical psychotic experiences. The bully climate of a school class moderates this effect, i.e., the higher risk for bullyvictims on subclinical psychotic experiences was less strong in classes with a higher percentage of classmates involved in bullying. Thus, bully climate has to be taken into account when studying the psychological experiences associated with being bullied. Keywords Bully climate Subclinical psychotic experiences Bullying Adolescents
E. M. B. Horrevorts K. Monshouwer W. A. M. Vollebergh (&) Faculty of Social and Behavioural Sciences, University of Utrecht, 80140, 3508 TC Utrecht, The Netherlands e-mail: [email protected] E. M. B. Horrevorts e-mail: [email protected] J. T. W. Wigman Department of Psychiatry and Psychology, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
Introduction Bullying is a widely known and occurring phenomenon on almost every school in The Netherlands [31]. Research indicates that 6.8 % of the high school children in The Netherlands report bullying twice a month or more and 6.4 % report being bullied twice a month or more [42]. Bullying is defined as repeated aggression, used by one or more students (the bullies) to deliberately hurt another student (the victim) physically, verbally or psychologically while the victim is incapable of defending himself. Teasing someone in a friendly manner or a quarrel between two students who have the same strength, is not defined as bullying [36]. The relationship between bullying and psychological health has been investigated in several studies [2, 8, 14, 22, 28, 30, 35, 40]. Many of these studies focused on emotional problems such as social anxiety, depression, aggression or suicide. However, little attention is paid to the relationship between bullying and subclinical psychotic experiences [5, 10, 24, 29, 37]. In addition, within the psychosis literature, the focus is often on trauma in general [e.g., 33, 44] and not specifically on bullying. Also, the relationship between the bullying climate in school classes and the mental health among students who bully or are bullied is rarely studied [23, 35, 45]. That is a significant omission, as it seems likely that the effects of being bullied depend also on the bullying context, with stronger effects for a child when bullying is a rare—and therefore possibly more personalized—phenomenon. The central question in this study is whether the presence of other students who bully or are bullied in a school class (the bully climate), is related to the prevalence of subclinical psychotic experiences among these students and if the bully climate moderates the relationship between bullying and subclinical psychotic experiences.
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The effects of bullying in childhood can be strong and long lasting. Children who were bullied at the beginning of a school year are at higher risk to develop a social anxiety disorder or to become depressive during the course of the next two school years, than children who were not bullied [8, 14, 30]. Several studies also revealed that bullying in childhood is related to the psychological health of people in adulthood [2, 8, 14, 22, 28, 35, 40]. In the worst case, bullying can even lead to suicide [2, 35]. Not only being bullied, but also acting in the role of bully can have consequences for an individual’s mental health: people who bully are at higher risk to become antisocial [30, 40] or develop a drinking problem [22]. The people with the highest risk of becoming antisocial or developing a drinking problem appear to be the ones who bully and are being bullied [22, 28, 40]. There are also several studies that focused more generally on the relation between (childhood) trauma (such as bullying and emotional/physical/psychological/sexual abuse or neglect) and subclinical psychotic experiences [3, 32, 33, 44]. These studies showed that being exposed to a traumatic experience was associated with an increased risk for psychosis and psychotic symptoms. Selten and colleagues [38] state that experiencing traumas can lead to feelings of social defeat, defined as ‘‘a negative experience of being excluded from the majority group’’. Social defeat, in turn, has been shown to be causally linked to schizophrenia [38]. Bullying, being a form of trauma where a person is being excluded from the majority of the group, can thus also lead to feelings of social defeat. Work of Werbelof and colleagues [46] and Fusar-Poli, Yung, McGorry and Van Os [15], shows that subclinical psychotic experiences may lead to clinical psychotic disorder. However, this association is not very strong, as a large part of subclinical psychotic experiences is transient and only a small proportion eventually evolves in psychotic disorders over time. It has been suggested that the link between incidental psychotic experiences and later clinical psychotic disorder is mediated by persistence of such experiences [12]. A suggested mechanism behind this process is sensitization [11], which suggests that on repeated exposure to stimuli of the same intensity the responses become increasingly stronger. Thus, in the current context, it can be hypothesized that on repeated exposure to bullying, the stress response becomes increasingly stronger, leading to more (proneness for) psychotic experiences. So far, only a few studies have focused on the association between bullying and subclinical psychotic experiences [5, 10, 24, 29, 37], but most of these studies focused only on the victims of bullying and not on the bullies [5, 10, 29, 37]. These studies showed that being bullied is associated with subclinical and clinical expressions of psychosis, reflected in symptoms such as hallucinations, delusions or feelings of paranoia. For example, the study of
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Bebbington et al. [5] revealed that being bullied in childhood was reported more often by participants with a psychotic disorder as compared to participants without a psychotic disorder. The studies mentioned above, were primarily focused on individual characteristics as precursors of bullying. However, there has been less attention for the influence of social context. This is an important omission, as the importance of social context has been, for instance, shown by studies conducted on the effect of ethnic density. The ethnic density effect is based on the assumption that living among members of one’s own ethnic group can work as a buffer against some of the negative influences related to being a member of a minority ethnic group [16]. Gieling and colleagues [16] showed that students who belong to an ethnic minority reporting higher levels of externalizing problem behavior, but only in classes with a minority of ethnic minority students and not in culturally diverse classes. Boydell and colleagues [9] found that the incidence of schizophrenia in non-white ethnic minorities increased significantly as the proportion of such minorities in the local population decreased. Some people rather speak of ‘group density’ instead of ‘ethnic density’ as the former also accounts for people who, for example, belong to the same religious group [19]. This phenomenon could also be applied to bullying behavior in classrooms. An important characteristic of the group density effect is that people need to have something in common. What they have in common ensures that they belong to the same group. Children who are being bullied share the fact that they are being bullied and thus belong to the same group: the victim group. It is reasonable to hypothesize that the effect of bullying might be stronger when children are the only one being bullied in a classroom. Some studies also showed that bystanders in a classroom are of great importance [23, 45]. If bullies are rejected by the bystanders, the bullying will decrease [45]: on the other hand, if bystanders do not defend the vulnerable students in a classroom, the effect of bullying might be stronger [23]. Thus, the context is of importance for the initiation, continuing, and ending of the bullying and as a consequence, can be of influence on the mental health of children who are involved in bullying. Thus, to our knowledge, most of the studies have only focused on the victims of bullying, but not on the bullies, in association with subclinical psychotic experiences. Moreover, not many studies have paid attention to the context of the classroom in association with bullying behavior. This study will be the first study that will focus on the different actors involved in bullying (bully, victim, bully-victim and the non-involved) in association to subclinical psychotic experiences and will also take the context of the classroom (the bully climate, i.e., the amount of bullying in a classroom) into account. The hypothesis is that there is an
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association between bullying and subclinical psychotic experiences, with adolescents who both bully and are being bullied (the bully-victims), report the highest levels of subclinical psychotic experiences. Importantly, an interaction of bully climate and bully type on the outcome of subclinical psychotic experiences is hypothesized: the more bullying behavior occurs in a classroom, the less effect it has on the psychotic experiences of bullies, victims, and bully-victims. The reverse is expected for the non-involved: the more bullying behavior occurs in a classroom, the more effect it has on the psychotic experiences of the non-involved.
Method Sample This study was conducted as part of the 2005 WHO crossnational study ‘‘health behavior in school-aged children’’ (HBSC), addressing health behaviors, health and its social context in children and adolescents in Europe and North America. In accordance with the HBSC guidelines, a twostage random sampling procedure was used [43]. First, schools were stratified according to level of urbanization. Second, schools were drawn proportionally to their number in the corresponding urbanization level. Third: within each school for secondary education, one class from every grade (1, 2, 3, 4) was selected randomly from a list of all classes provided by every participating school. Response rate at school level was 47 % (N = 64). Non-response could mainly be attributed to other research already going on in the school (38 %), or too many requests to participate in research projects (26 %). Participating and non-participating schools did not differ with respect to school size, school levels, urbanization level, or percentage of ethnic minorities at the school. Response rate at student level was 93 %. Absence of children during the data collection was primarily due to sick leave. Data were collected in October– November 2005. Participants who had more than four items missing on the questions on the CAPE (community assessment of psychic experiences (CAPE) positive experiences scale), assessing subclinical psychotic experiences were excluded (816 cases, 14.8 %). Missing data for participants with a maximum of four items missing on the CAPE (353 cases with the majority (209) missing one item) were imputed using multiple imputation. Excluded cases did not differ from those that were included in the analyses with respect to gender and socio-economic status (as assessed with the family affluence scale) [13]. However, they did differ with respect to school level, psychosocial problems [as measured with the strength and difficulties questionnaire (SDQ)] [17], bully type and bully
climate. Those who were excluded from the analyses more often attended schools with a lower level of education, were in classes with a higher percentage of bully-victims and a higher percentage of classmates involved in bullying. Furthermore, the SDQ-score was higher in the excluded group, indicating more psychosocial problems. For this study, only participants who completed the CAPE and bullying questions were included. This procedure resulted in a sample of 4,582 respondents aged 12–16 years (mean age 14.0; SD 1.3; 49.8 % girls). Data collection All data were collected by means of questionnaires, which were distributed in classes and administered by a trained research assistant, during a lesson (usually 50 min). When introducing the questionnaire, the research assistant emphasized the anonymity of the respondents and explained that participation in the study was voluntary. Collecting all questionnaires in one envelope and sealing the envelope in the presence of the respondents further ensured anonymity. Furthermore, the research assistants stressed that the students could ask for help in case something in the questionnaire was not clear to them.
Measures Bullying Children can be involved in bullying as a bully and/or as a victim of bullying. In the present study, this was assessed by the following two questions: (1) how often have you been bullied in school in the last 2 months? and (2) how often have you been bullying another student in school in the last 2 months? The questions on bullying were introduced with the following explanation: ‘‘someone is a victim of bullying if someone else, or a group of students, says or does something nasty to him or her. Bullying is also repeatedly teasing someone in a way the person finds unpleasant or to deliberately exclude someone from the group. Bullying is not when two students who are approximately the same height and have the same strength are having a quarrel or fight. Teasing someone in a friendly or playful way is also not bullying’’. Respondents reporting to bully or being bullied at least once a week were considered a bully or, respectively, a victim [43]. Respondents reporting to bully and being bullied at least once a week were considered a bully-victim. And respondents reporting to bully or being bullied less then once a week were considered non-involved. Based on these variables, a new variable was created categorizing all respondents in one of
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the four categories: bully, victim, bully-victim, noninvolved. Bully climate Bully climate refers to the prevalence of bullying in a classroom (a continuous measure calculated as the percentage of students in the class who were involved in bullying, either as a bully, victim, or bully-victim). Subclinical psychotic experiences Subclinical psychotic experiences refer to thoughts as hallucinations and delusions [47] and are a milder form of the clinical form of psychotic symptoms. This was measured with the CAPE positive experiences scale. [27, 41]. This scale consists of 20 items whereby the participant is asked about the frequency of certain thoughts and feelings, for example: ‘‘do you sometimes hear voices, while being alone? (not from radio or tv)’’ or ‘‘do you see things, people or animals which other people don’t see’’. When introducing the questionnaire, the research assistants stressed that not everyone might experience these symptoms and that it is important that everyone completes all items seriously. Answers could be given on a four-point scale, which were (1) never, (2) sometimes, (3) often, and (4) almost every time. For each participant, an average sum score was calculated (range 1–4). Higher scores indicate a higher occurrence of subclinical psychotic experiences. The internal consistency in our sample was high (a = 0.94). Analysis The data in this study are hierarchically structured, i.e., students are nested within classes, which are nested within schools. In such a hierarchical structure, standard statistical formulas will underestimate the sampling variance, and consequently lead to significance tests with an inflated alpha level (type 1 error rate) [21]. Thus, ignoring the multilevel structure of the data would lead to spuriously significant effects. Multilevel models are specifically geared toward the statistical analyses of nested clustered data [21] and therefore multilevel analyses are the appropriate techniques for the present study. As we were primarily interested in the associations between class characteristics and individual level outcomes, we only used the class level above the individual level in our analysis. The analyses were performed in three steps: first a socalled null model was fitted, i.e., a model with only an intercept (the overall mean of psychotic symptoms across classes) and random class effects. This model allowed us to calculate which part of the total variance in the outcome
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variable (psychotic symptoms), can be attributed to the higher level (class). In a second model, we tested the relationship between bully type and psychotic symptoms, assuming that this effect is the same in all classes (fixed effects). To test if the effect of bully type and psychotic symptoms differed across classes, a likelihood ratio test was performed comparing the fit of the second model with a model in which the effect of bully type was allowed to vary randomly across classes. If so, in a final model, including a cross-level interaction term, we assessed to what extent class differences in the relationship between bully type and psychotic symptoms could be explained by the bully climate in a class. All analyses were performed using Stata version SE 11.1. We used the default estimation procedure in Stata, i.e., the expectation maximization algorithm until convergence (or 20 iterations have been reached). At that point, maximization switches to a gradient-based method (modified Newton–Raphson). For the random slope models, the default setting of Stata was used, i.e., the variances of the slope and intercept were assumed to be independent.
Results Descriptives The majority of the respondents (86.8 %) were not involved in bullying. Of the remaining respondents, the majority were bullies (7.3 %), followed by victims (4.7 %), and a small group of respondents (1.2 %) who were both bully and victim. In General, boys (16.4 %) were more involved in bullying behavior than girls (10.0 %), which is most remarkable in the categories bully and bully-victim. Gender differences in the percentage of victims were almost absent (Table 1). Table 2 shows the mean scores on subclinical psychotic experiences. Girls have a significant higher mean score on subclinical psychotic experiences than boys (girls 1.40, boys 1.32). When the different bully categories are compared, bully-victims and victims appear to report the highest scores
Table 1 The distribution of bully type and age divided by sex Sex
Age
Bully type
M
SE
Bully
Victim
Bullyvictim
Noninvolved
Male
14.9
1.4
222 (9.7)
111 (4.8)
42 (1.8)
1,914 (83.6)
Female
14.1
1.3
111 (4.8)
105 (4.6)
13 (0.6)
2,064 (90.0)
Total
14.5
1.3
333 (7.3)
216 (4.7)
55 (1.2)
3,978 (86.8)
Values are N (%)
Eur Child Adolesc Psychiatry Table 2 The average score and SE on subclinical psychotic experiences divided by sex and bully type Item
N
Subclinical psychotic experiences M (SE)
Male
2,289
1.32 (0.28)a
Female Total
2,293 4,582
1.40 (0.29) 1.36 (0.29)
Sex
Bully type Bully
333
1.45 (0.33)b
Victim
216
1.53 (0.35)b
55
1.59 (0.38)b
Bully-victim Non-involved
3,978
1.34 (0.28)
a
Difference with girls is significant (p \ 0.05)
b
Difference with non-involved is significant (p \ 0.05)
and the non-involved report the lowest scores. Results on the class level variable ‘bully climate’, show that students in a class with a high bully climate report significant higher scores on subclinical psychotic experiences than students in a class with a low bully climate. Associations between bullying and subclinical psychotic experiences Table 3 shows the association between bully type and bully climate and the outcome variable of subclinical psychotic experiences in three different models.
Model 1: The results of the null model (including only an intercept and random class effects) show that the overall mean score of subclinical psychotic experiences across classes is 1.36. The random part of the model allows us to partition the variance in individual and class level variance. The results indicate that 3.9 % of the variance can be attributed to differences between classes. A likelihood ratio test comparing the null multilevel model with a null singlelevel model, indicated that the class effect was significant (chibar2(01) = 43.50, p = 0.0000). Model 2: This model tests the relationship between bully type and psychotic symptoms, assuming that this effect is the same in all classes. The results indicate that compared to the noninvolved, all bully types are associated with a higher score on subclinical psychotic experiences. The effect appears to be most strong among the bully-victims (b = 0.26), followed by the victims (b = 0.19), and the bullies (b = 0.10). In a next step, the effects of bully type were allowed to vary across classes. The likelihood ratio test statistic, comparing a model in which effects of bully type were allowed to vary across classes with a model in which these effects were fixed, indicated that the effect of bully type differed across classes (LR = 34 on 3 df, p \ 0.001). Model 3: In a final model, it was tested whether these differences across classes could be explained by the bully climate. The cross-level interaction term of bully climate and bully type, was small but significant, (b = -0.0044, p \ 0.05), indicating that the effect of being a bully-victim on subclinical psychotic experiences, was less strong in
Table 3 The relationship between bully type, bully climate, and subclinical psychotic experiences Fixed effects
Model 1
Model 2
Model 3
Coeff.
SE
Coeff.
SE
Coeff.
SE
1.363
0.006
1.343
0.006
1.336
0.009
Bully
0.103
0.016
0.118
0.023
Victim
0.190
0.020
0.219
0.029
0.257
0.039
0.328 -0.002
0.060 0.002
Intercept Bully types
Bully-victim Bully climate 9 bully Bully climate 9 victim
20.004
-0.002
Bully climate 9 bully-victim
-0.006
0.004
Random effects Intercept
0.003
0.000
0.003
0.001
Bully climate 9 bully
0.003
0.001
0.014
0.006
Bully climate 9 victim
0.029
0.011
Bully climate 9 bully-victim
0.046
0.027
0.077
0.002
Residual
0.082
0.002
0.079
0.002
Model 1: null model (random intercept) Model 2: random intercept and fixed effects of bully type Model 3: random intercept, cross-level interaction of bully type, and bully climate Bold: P \ 0.0001, except for interaction terms: P \ 0.05
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classes with higher levels of bully climate (i.e., a higher percentage of classmates involved in bullying).
Discussion This study aimed to examine the association between bullying in school classes and the prevalence of subclinical psychotic experiences among students who bully or are being bullied, hereby also analyzing whether the presence of other students who bully or are being bullied in a school class (the bully climate) moderates the relationship between bullying and psychotic experiences. Although the prevalence of subclinical psychotic experiences is low, a clear effect of being involved in bullying is found, with children who are involved in bullying reporting higher levels of subclinical psychotic experiences than non-involved children. Bully-victims and victims report the highest levels of subclinical psychotic experiences, (a mean score of, respectively, 1.59 (SE = 0.38) and 1.53 (SE = 0.35) on the CAPE) which is in line with previous research on the effect of bullying on psychotic problems [22, 28, 40]. This can partly be explained by the fact that the characteristics of bullied children also enhance their risk of becoming ensnared in bullying experiences on the one hand, while making them vulnerable for the effects of bullying at the same time. Bullies are often impulsive and aggressive toward their environment [1, 40]. They often show other problem behavior as well, as expressed in higher prevalences of conduct disorder [1, 2]. It is possible that they are more sensitive to developing psychotic phenomena, like subclinical psychotic experiences, than non-involved children, as patterns of antisocial behavior in childhood and early adolescence have been observed prior to the onset of schizophrenia [20, 25]. Victims are often insecure, withdrawn and have a negative self-image [1]. Previous research showed that psychotic experiences such as hallucinations and delusions are associated with a low selfesteem [4] and paranoia with negative interpersonal beliefs, which are associated with previous (negative) interpersonal experiences [6, 7, 26]. Although the mentioned studies focused on family relations, bullying can also be seen as a negative interpersonal experience. Paranoid delusions have been described as an extreme method to maintain selfesteem in individuals with a low self-esteem [6]. Bullyvictims are seen as the most troubled. They are aggressive, like bullies, but also have internalizing problems and a negative self-image, like victims [40]. Their personality appears to be the most disturbed, because they have got contradictory meanings about themselves. They feel powerful but at the same time mention numerous negative characteristics [22]. In a study of Mynard and Joseph [34] who studied the association of personality dimensions with
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bullying, bully-victims differed from both bullies and victims on some dimensions as social acceptance and neuroticism, but in general were seen as closer reminiscent of bullies than victims. Like bullies, it is also possible for bully-victims that they are more sensitive to developing psychotic phenomena, like subclinical psychotic experiences, than non-involved children. The bully climate of a classroom can moderate the effect of bullying on subclinical psychotic experiences, in particular of victims. Our study showed that the higher the bully climate, the less subclinical psychotic experiences were associated with being bullied (b = -0.004). It could be hypothesized that in these classes victims find more support from other victims, which may buffer the negative effect of bullying on their psychological functioning. Victims may reach out for each other and get support from the fact that they are not the only ones who are being bullied. This is in line with the ethnic or group density hypothesis. Support for this hypothesis is found by Nishina and Juvonen [35] who found that victims of bullying reported higher levels of anxiety and had a lower self-esteem than children who were not bullied. However, when they witnessed someone else being bullied, they felt less anxious and had a higher self-esteem on days when they were bullied themselves. They only felt humiliated and angry when they saw themselves as lone targets. Some victims blame themselves for being bullied [18]. Witnessing someone else being bullied in a classroom could also reduce their thoughts of self-blame: ‘‘it’s not only me, so i’m not the one to blame’’. This could also partly explain the fact that the interaction with bully climate is only found for victims and not for bullies and bully-victims. Victims are personally affected when they are being bullied, as some of them tend to blame themselves for it. The more other kids are being bullied, the less they need to blame themselves [18] and thus the less it may personally affect them. Another explanation is more focused on bullying as a group phenomenon. Sentse et al. [39] conducted a study on the effect of bullying in a classroom on peer preference. It showed that in a classroom where bullying is non-normative (there are not many victims), both victims and bullies are rejected by the group. In a classroom where bullying is normative (there are many victims), victims are still rejected by their classmates (although slightly less than in a classroom where bullying is non-normative), while bullies are more preferred by their classmates. Thus, the average behavior of classmates determines whether you will be accepted in a classroom or not.
Implications First of all, it is important to point out that bullying cannot be justified and should always be prevented. Although a
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high amount of bullying in classes seems to benefit the victims, the average score on subclinical psychotic experiences, even in classes where bullying is more common, is still higher in involved than in non-involved children. Both teachers and students should be aware of the (long-term) effect of bullying on the mental health of victims. Our results suggest that it is important for victims in classes where bullying is not quite common, to get into contact with co-victims. This could give them some support. Subsequently, knowing they are not the only ones could reduce their thoughts of self-blame, negative selfimage, and low self-esteem, which could reduce their paranoid delusions (their extreme method to maintain selfesteem).
Limitations A number of limitations of this study need to be mentioned. The first limitation concerns the measurement of bullying and subclinical psychotic experiences. Bullying and subclinical psychotic experiences are measured by self-report, which can lead to incorrect or social desirable answers. A second limitation is the fact that the data are cross-sectional and therefore we cannot disentangle the temporal relationship between subclinical psychotic experiences and bully climate and no inferences can be made on causality. Furthermore, those who were excluded from the analyses because of missing items on the CAPE, differed from those included in the analyses on a number of characteristics (e.g., excluded cases were more often bully-victims and more often attended classes with a high bully climate). Therefore, we may have underestimated the strength of the relationship between bullying and subclinical psychotic experiences. The prevalence of bullying types was rather low, with small percentage of students being bully-victim. Lack of power may explain the fact that we only found significant interactions between bullying climate and being a victim. A final limitation is that the questions about bullying are asked about the school (and not specifically the class), so it is not clear whether the victims stay in the same class as their bullies or not. On the other hand, students in the same class are together more often and it is likely that reported bullying takes place in this context. Conflict of interest On behalf of all authors, the corresponding author states that there is no conflict of interest.
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35. Nishina A, Juvonen J (2005) Daily reports of witnessing and experiencing peer harassment in middle school. Child Dev 76:435–450 36. Olweus D (1997) Bully/victim problems in school: facts and intervention. Eur J Psychol Educ XII:495–510 37. Schreier A, Wolke D, Thomas K, Horwood J, Hollis C, Gunnell D, Lewis G, Thompson A, Zammit S, Duffy L, Salvi G, Harrison G (2009) Prospective study of peer victimization in childhood and psychotic symptoms in a nonclinical population at age 12 years. Arch Gen Psychiatry 66:527–536 38. Selten J, Van der Ven E, Rutten BPF, Cantor-Graae E (2013) The social defeat hypothesis of schizophrenia: an update. Schizophr Bull 39:1180–1186 39. Sentse M, Rl Scholte, Salmivalli C, Voeten M (2007) Persongroup dissimilarity in involvement in bullying and its relation with social status. J Abnorm Child Psych 35:1009–1019 40. Sourander A, Jensen P, Ro¨nning JA, Niemela¨ S, Helenius H, Sillanma¨ki L, Kumpulainen K, Piha J, Tamminen T, Moilanen I, Almqvist F (2007) What is the early adulthood outcome of boys who bully or are bullied in childhood? the finnish ‘‘from a boy to a man’’ study. Pediatrics 120:397–404 41. Stefanis NC, Hanssen M, Smyrnis N, Avramopoulos D, Evdokimidis I, Stefanis CN, Verdoux H, Van Os J (2002) Evidence that three dimensions of psychosis have a distribution in the general population. Psychol Med 32:347–358 42. Van Dorsselaer S, De Looze M, Vermeulen-Smit E, De Roos S, Verdurmen J, Ter Bogt T, Vollebergh W (2010) HBSC 2009 Gezondheid, welzijn en opvoeding van jongeren in Nederland. Trimbos-Instituut, Utrecht 43. Van Dorsselaer S, Zeijl E, Van den Eeckhout S, Ter Bogt T, Vollebergh WAM (2007) HBSC 2005 Gezondheid en welzijn van jongeren in Nederland. Trimbos-Instituut, Utrecht 44. Varese F, Smeets F, Drukker M, Lieverse R, Lataster T, Viechtbauer W, Read J, Van Os J, Bentall RP (2012) Childhood adversities increase the risk of psychosis: a meta-analysis of patient-control, prospective- and cross-sectional cohort studies. Schizophr Bull 38:661–671 45. Veenstra R, Huitsing G, Dijkstra JK, Lindenberg S (2008) Wie pest wie? Een netwerkbenadering van pesten. Justitie¨le Verkenning 34:78–92 46. Werbelof N, Drukker M, Dohrenwend BP, Levav I, Yoffe R, Van Os J, Davidson M, Weiser M (2012) Self-reported attenuated psychotic symptoms as forerunners of severe mental disorders later in life. Arch Gen Psychiatry 69(5):467–475 47. Wigman JTW, Vollebergh WAM, Raaijmakers QAW, Iedema J, Van Dorsselaer S, Ormel J, Verhulst FC, Van Os J (2011) The structure of the extended psychosis phenotype in early adolescence—a cross-sample replication. Schizophr Bull 37:850–860
ORIGINAL CONTRIBUTION
The relation between bullying and subclinical psychotic experiences and the influence of the bully climate of school classes Esther M. B. Horrevorts • Karin Monshouwer • Johanna T. W. Wigman • Wilma A. M. Vollebergh
Received: 13 May 2013 / Accepted: 27 January 2014 Ó Springer-Verlag Berlin Heidelberg 2014
Abstract This study aims to examine the association between the bully climate of school classes and the prevalence of subclinical psychotic experiences among students who are involved in bullying (either as bully or as victim). Data were derived from the Dutch health behavior in school-aged children survey of 2005, a nationally representative cross-sectional study with a total of 5,509 adolescents between the age of 12 and 16. The data were analyzed using a multilevel regression analysis. The study revealed that both bullying and being bullied in school classes was associated with an increased level of subclinical psychotic experiences. The bully climate of a school class moderates this effect, i.e., the higher risk for bullyvictims on subclinical psychotic experiences was less strong in classes with a higher percentage of classmates involved in bullying. Thus, bully climate has to be taken into account when studying the psychological experiences associated with being bullied. Keywords Bully climate Subclinical psychotic experiences Bullying Adolescents
E. M. B. Horrevorts K. Monshouwer W. A. M. Vollebergh (&) Faculty of Social and Behavioural Sciences, University of Utrecht, 80140, 3508 TC Utrecht, The Netherlands e-mail: [email protected] E. M. B. Horrevorts e-mail: [email protected] J. T. W. Wigman Department of Psychiatry and Psychology, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
Introduction Bullying is a widely known and occurring phenomenon on almost every school in The Netherlands [31]. Research indicates that 6.8 % of the high school children in The Netherlands report bullying twice a month or more and 6.4 % report being bullied twice a month or more [42]. Bullying is defined as repeated aggression, used by one or more students (the bullies) to deliberately hurt another student (the victim) physically, verbally or psychologically while the victim is incapable of defending himself. Teasing someone in a friendly manner or a quarrel between two students who have the same strength, is not defined as bullying [36]. The relationship between bullying and psychological health has been investigated in several studies [2, 8, 14, 22, 28, 30, 35, 40]. Many of these studies focused on emotional problems such as social anxiety, depression, aggression or suicide. However, little attention is paid to the relationship between bullying and subclinical psychotic experiences [5, 10, 24, 29, 37]. In addition, within the psychosis literature, the focus is often on trauma in general [e.g., 33, 44] and not specifically on bullying. Also, the relationship between the bullying climate in school classes and the mental health among students who bully or are bullied is rarely studied [23, 35, 45]. That is a significant omission, as it seems likely that the effects of being bullied depend also on the bullying context, with stronger effects for a child when bullying is a rare—and therefore possibly more personalized—phenomenon. The central question in this study is whether the presence of other students who bully or are bullied in a school class (the bully climate), is related to the prevalence of subclinical psychotic experiences among these students and if the bully climate moderates the relationship between bullying and subclinical psychotic experiences.
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The effects of bullying in childhood can be strong and long lasting. Children who were bullied at the beginning of a school year are at higher risk to develop a social anxiety disorder or to become depressive during the course of the next two school years, than children who were not bullied [8, 14, 30]. Several studies also revealed that bullying in childhood is related to the psychological health of people in adulthood [2, 8, 14, 22, 28, 35, 40]. In the worst case, bullying can even lead to suicide [2, 35]. Not only being bullied, but also acting in the role of bully can have consequences for an individual’s mental health: people who bully are at higher risk to become antisocial [30, 40] or develop a drinking problem [22]. The people with the highest risk of becoming antisocial or developing a drinking problem appear to be the ones who bully and are being bullied [22, 28, 40]. There are also several studies that focused more generally on the relation between (childhood) trauma (such as bullying and emotional/physical/psychological/sexual abuse or neglect) and subclinical psychotic experiences [3, 32, 33, 44]. These studies showed that being exposed to a traumatic experience was associated with an increased risk for psychosis and psychotic symptoms. Selten and colleagues [38] state that experiencing traumas can lead to feelings of social defeat, defined as ‘‘a negative experience of being excluded from the majority group’’. Social defeat, in turn, has been shown to be causally linked to schizophrenia [38]. Bullying, being a form of trauma where a person is being excluded from the majority of the group, can thus also lead to feelings of social defeat. Work of Werbelof and colleagues [46] and Fusar-Poli, Yung, McGorry and Van Os [15], shows that subclinical psychotic experiences may lead to clinical psychotic disorder. However, this association is not very strong, as a large part of subclinical psychotic experiences is transient and only a small proportion eventually evolves in psychotic disorders over time. It has been suggested that the link between incidental psychotic experiences and later clinical psychotic disorder is mediated by persistence of such experiences [12]. A suggested mechanism behind this process is sensitization [11], which suggests that on repeated exposure to stimuli of the same intensity the responses become increasingly stronger. Thus, in the current context, it can be hypothesized that on repeated exposure to bullying, the stress response becomes increasingly stronger, leading to more (proneness for) psychotic experiences. So far, only a few studies have focused on the association between bullying and subclinical psychotic experiences [5, 10, 24, 29, 37], but most of these studies focused only on the victims of bullying and not on the bullies [5, 10, 29, 37]. These studies showed that being bullied is associated with subclinical and clinical expressions of psychosis, reflected in symptoms such as hallucinations, delusions or feelings of paranoia. For example, the study of
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Bebbington et al. [5] revealed that being bullied in childhood was reported more often by participants with a psychotic disorder as compared to participants without a psychotic disorder. The studies mentioned above, were primarily focused on individual characteristics as precursors of bullying. However, there has been less attention for the influence of social context. This is an important omission, as the importance of social context has been, for instance, shown by studies conducted on the effect of ethnic density. The ethnic density effect is based on the assumption that living among members of one’s own ethnic group can work as a buffer against some of the negative influences related to being a member of a minority ethnic group [16]. Gieling and colleagues [16] showed that students who belong to an ethnic minority reporting higher levels of externalizing problem behavior, but only in classes with a minority of ethnic minority students and not in culturally diverse classes. Boydell and colleagues [9] found that the incidence of schizophrenia in non-white ethnic minorities increased significantly as the proportion of such minorities in the local population decreased. Some people rather speak of ‘group density’ instead of ‘ethnic density’ as the former also accounts for people who, for example, belong to the same religious group [19]. This phenomenon could also be applied to bullying behavior in classrooms. An important characteristic of the group density effect is that people need to have something in common. What they have in common ensures that they belong to the same group. Children who are being bullied share the fact that they are being bullied and thus belong to the same group: the victim group. It is reasonable to hypothesize that the effect of bullying might be stronger when children are the only one being bullied in a classroom. Some studies also showed that bystanders in a classroom are of great importance [23, 45]. If bullies are rejected by the bystanders, the bullying will decrease [45]: on the other hand, if bystanders do not defend the vulnerable students in a classroom, the effect of bullying might be stronger [23]. Thus, the context is of importance for the initiation, continuing, and ending of the bullying and as a consequence, can be of influence on the mental health of children who are involved in bullying. Thus, to our knowledge, most of the studies have only focused on the victims of bullying, but not on the bullies, in association with subclinical psychotic experiences. Moreover, not many studies have paid attention to the context of the classroom in association with bullying behavior. This study will be the first study that will focus on the different actors involved in bullying (bully, victim, bully-victim and the non-involved) in association to subclinical psychotic experiences and will also take the context of the classroom (the bully climate, i.e., the amount of bullying in a classroom) into account. The hypothesis is that there is an
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association between bullying and subclinical psychotic experiences, with adolescents who both bully and are being bullied (the bully-victims), report the highest levels of subclinical psychotic experiences. Importantly, an interaction of bully climate and bully type on the outcome of subclinical psychotic experiences is hypothesized: the more bullying behavior occurs in a classroom, the less effect it has on the psychotic experiences of bullies, victims, and bully-victims. The reverse is expected for the non-involved: the more bullying behavior occurs in a classroom, the more effect it has on the psychotic experiences of the non-involved.
Method Sample This study was conducted as part of the 2005 WHO crossnational study ‘‘health behavior in school-aged children’’ (HBSC), addressing health behaviors, health and its social context in children and adolescents in Europe and North America. In accordance with the HBSC guidelines, a twostage random sampling procedure was used [43]. First, schools were stratified according to level of urbanization. Second, schools were drawn proportionally to their number in the corresponding urbanization level. Third: within each school for secondary education, one class from every grade (1, 2, 3, 4) was selected randomly from a list of all classes provided by every participating school. Response rate at school level was 47 % (N = 64). Non-response could mainly be attributed to other research already going on in the school (38 %), or too many requests to participate in research projects (26 %). Participating and non-participating schools did not differ with respect to school size, school levels, urbanization level, or percentage of ethnic minorities at the school. Response rate at student level was 93 %. Absence of children during the data collection was primarily due to sick leave. Data were collected in October– November 2005. Participants who had more than four items missing on the questions on the CAPE (community assessment of psychic experiences (CAPE) positive experiences scale), assessing subclinical psychotic experiences were excluded (816 cases, 14.8 %). Missing data for participants with a maximum of four items missing on the CAPE (353 cases with the majority (209) missing one item) were imputed using multiple imputation. Excluded cases did not differ from those that were included in the analyses with respect to gender and socio-economic status (as assessed with the family affluence scale) [13]. However, they did differ with respect to school level, psychosocial problems [as measured with the strength and difficulties questionnaire (SDQ)] [17], bully type and bully
climate. Those who were excluded from the analyses more often attended schools with a lower level of education, were in classes with a higher percentage of bully-victims and a higher percentage of classmates involved in bullying. Furthermore, the SDQ-score was higher in the excluded group, indicating more psychosocial problems. For this study, only participants who completed the CAPE and bullying questions were included. This procedure resulted in a sample of 4,582 respondents aged 12–16 years (mean age 14.0; SD 1.3; 49.8 % girls). Data collection All data were collected by means of questionnaires, which were distributed in classes and administered by a trained research assistant, during a lesson (usually 50 min). When introducing the questionnaire, the research assistant emphasized the anonymity of the respondents and explained that participation in the study was voluntary. Collecting all questionnaires in one envelope and sealing the envelope in the presence of the respondents further ensured anonymity. Furthermore, the research assistants stressed that the students could ask for help in case something in the questionnaire was not clear to them.
Measures Bullying Children can be involved in bullying as a bully and/or as a victim of bullying. In the present study, this was assessed by the following two questions: (1) how often have you been bullied in school in the last 2 months? and (2) how often have you been bullying another student in school in the last 2 months? The questions on bullying were introduced with the following explanation: ‘‘someone is a victim of bullying if someone else, or a group of students, says or does something nasty to him or her. Bullying is also repeatedly teasing someone in a way the person finds unpleasant or to deliberately exclude someone from the group. Bullying is not when two students who are approximately the same height and have the same strength are having a quarrel or fight. Teasing someone in a friendly or playful way is also not bullying’’. Respondents reporting to bully or being bullied at least once a week were considered a bully or, respectively, a victim [43]. Respondents reporting to bully and being bullied at least once a week were considered a bully-victim. And respondents reporting to bully or being bullied less then once a week were considered non-involved. Based on these variables, a new variable was created categorizing all respondents in one of
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the four categories: bully, victim, bully-victim, noninvolved. Bully climate Bully climate refers to the prevalence of bullying in a classroom (a continuous measure calculated as the percentage of students in the class who were involved in bullying, either as a bully, victim, or bully-victim). Subclinical psychotic experiences Subclinical psychotic experiences refer to thoughts as hallucinations and delusions [47] and are a milder form of the clinical form of psychotic symptoms. This was measured with the CAPE positive experiences scale. [27, 41]. This scale consists of 20 items whereby the participant is asked about the frequency of certain thoughts and feelings, for example: ‘‘do you sometimes hear voices, while being alone? (not from radio or tv)’’ or ‘‘do you see things, people or animals which other people don’t see’’. When introducing the questionnaire, the research assistants stressed that not everyone might experience these symptoms and that it is important that everyone completes all items seriously. Answers could be given on a four-point scale, which were (1) never, (2) sometimes, (3) often, and (4) almost every time. For each participant, an average sum score was calculated (range 1–4). Higher scores indicate a higher occurrence of subclinical psychotic experiences. The internal consistency in our sample was high (a = 0.94). Analysis The data in this study are hierarchically structured, i.e., students are nested within classes, which are nested within schools. In such a hierarchical structure, standard statistical formulas will underestimate the sampling variance, and consequently lead to significance tests with an inflated alpha level (type 1 error rate) [21]. Thus, ignoring the multilevel structure of the data would lead to spuriously significant effects. Multilevel models are specifically geared toward the statistical analyses of nested clustered data [21] and therefore multilevel analyses are the appropriate techniques for the present study. As we were primarily interested in the associations between class characteristics and individual level outcomes, we only used the class level above the individual level in our analysis. The analyses were performed in three steps: first a socalled null model was fitted, i.e., a model with only an intercept (the overall mean of psychotic symptoms across classes) and random class effects. This model allowed us to calculate which part of the total variance in the outcome
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variable (psychotic symptoms), can be attributed to the higher level (class). In a second model, we tested the relationship between bully type and psychotic symptoms, assuming that this effect is the same in all classes (fixed effects). To test if the effect of bully type and psychotic symptoms differed across classes, a likelihood ratio test was performed comparing the fit of the second model with a model in which the effect of bully type was allowed to vary randomly across classes. If so, in a final model, including a cross-level interaction term, we assessed to what extent class differences in the relationship between bully type and psychotic symptoms could be explained by the bully climate in a class. All analyses were performed using Stata version SE 11.1. We used the default estimation procedure in Stata, i.e., the expectation maximization algorithm until convergence (or 20 iterations have been reached). At that point, maximization switches to a gradient-based method (modified Newton–Raphson). For the random slope models, the default setting of Stata was used, i.e., the variances of the slope and intercept were assumed to be independent.
Results Descriptives The majority of the respondents (86.8 %) were not involved in bullying. Of the remaining respondents, the majority were bullies (7.3 %), followed by victims (4.7 %), and a small group of respondents (1.2 %) who were both bully and victim. In General, boys (16.4 %) were more involved in bullying behavior than girls (10.0 %), which is most remarkable in the categories bully and bully-victim. Gender differences in the percentage of victims were almost absent (Table 1). Table 2 shows the mean scores on subclinical psychotic experiences. Girls have a significant higher mean score on subclinical psychotic experiences than boys (girls 1.40, boys 1.32). When the different bully categories are compared, bully-victims and victims appear to report the highest scores
Table 1 The distribution of bully type and age divided by sex Sex
Age
Bully type
M
SE
Bully
Victim
Bullyvictim
Noninvolved
Male
14.9
1.4
222 (9.7)
111 (4.8)
42 (1.8)
1,914 (83.6)
Female
14.1
1.3
111 (4.8)
105 (4.6)
13 (0.6)
2,064 (90.0)
Total
14.5
1.3
333 (7.3)
216 (4.7)
55 (1.2)
3,978 (86.8)
Values are N (%)
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N
Subclinical psychotic experiences M (SE)
Male
2,289
1.32 (0.28)a
Female Total
2,293 4,582
1.40 (0.29) 1.36 (0.29)
Sex
Bully type Bully
333
1.45 (0.33)b
Victim
216
1.53 (0.35)b
55
1.59 (0.38)b
Bully-victim Non-involved
3,978
1.34 (0.28)
a
Difference with girls is significant (p \ 0.05)
b
Difference with non-involved is significant (p \ 0.05)
and the non-involved report the lowest scores. Results on the class level variable ‘bully climate’, show that students in a class with a high bully climate report significant higher scores on subclinical psychotic experiences than students in a class with a low bully climate. Associations between bullying and subclinical psychotic experiences Table 3 shows the association between bully type and bully climate and the outcome variable of subclinical psychotic experiences in three different models.
Model 1: The results of the null model (including only an intercept and random class effects) show that the overall mean score of subclinical psychotic experiences across classes is 1.36. The random part of the model allows us to partition the variance in individual and class level variance. The results indicate that 3.9 % of the variance can be attributed to differences between classes. A likelihood ratio test comparing the null multilevel model with a null singlelevel model, indicated that the class effect was significant (chibar2(01) = 43.50, p = 0.0000). Model 2: This model tests the relationship between bully type and psychotic symptoms, assuming that this effect is the same in all classes. The results indicate that compared to the noninvolved, all bully types are associated with a higher score on subclinical psychotic experiences. The effect appears to be most strong among the bully-victims (b = 0.26), followed by the victims (b = 0.19), and the bullies (b = 0.10). In a next step, the effects of bully type were allowed to vary across classes. The likelihood ratio test statistic, comparing a model in which effects of bully type were allowed to vary across classes with a model in which these effects were fixed, indicated that the effect of bully type differed across classes (LR = 34 on 3 df, p \ 0.001). Model 3: In a final model, it was tested whether these differences across classes could be explained by the bully climate. The cross-level interaction term of bully climate and bully type, was small but significant, (b = -0.0044, p \ 0.05), indicating that the effect of being a bully-victim on subclinical psychotic experiences, was less strong in
Table 3 The relationship between bully type, bully climate, and subclinical psychotic experiences Fixed effects
Model 1
Model 2
Model 3
Coeff.
SE
Coeff.
SE
Coeff.
SE
1.363
0.006
1.343
0.006
1.336
0.009
Bully
0.103
0.016
0.118
0.023
Victim
0.190
0.020
0.219
0.029
0.257
0.039
0.328 -0.002
0.060 0.002
Intercept Bully types
Bully-victim Bully climate 9 bully Bully climate 9 victim
20.004
-0.002
Bully climate 9 bully-victim
-0.006
0.004
Random effects Intercept
0.003
0.000
0.003
0.001
Bully climate 9 bully
0.003
0.001
0.014
0.006
Bully climate 9 victim
0.029
0.011
Bully climate 9 bully-victim
0.046
0.027
0.077
0.002
Residual
0.082
0.002
0.079
0.002
Model 1: null model (random intercept) Model 2: random intercept and fixed effects of bully type Model 3: random intercept, cross-level interaction of bully type, and bully climate Bold: P \ 0.0001, except for interaction terms: P \ 0.05
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classes with higher levels of bully climate (i.e., a higher percentage of classmates involved in bullying).
Discussion This study aimed to examine the association between bullying in school classes and the prevalence of subclinical psychotic experiences among students who bully or are being bullied, hereby also analyzing whether the presence of other students who bully or are being bullied in a school class (the bully climate) moderates the relationship between bullying and psychotic experiences. Although the prevalence of subclinical psychotic experiences is low, a clear effect of being involved in bullying is found, with children who are involved in bullying reporting higher levels of subclinical psychotic experiences than non-involved children. Bully-victims and victims report the highest levels of subclinical psychotic experiences, (a mean score of, respectively, 1.59 (SE = 0.38) and 1.53 (SE = 0.35) on the CAPE) which is in line with previous research on the effect of bullying on psychotic problems [22, 28, 40]. This can partly be explained by the fact that the characteristics of bullied children also enhance their risk of becoming ensnared in bullying experiences on the one hand, while making them vulnerable for the effects of bullying at the same time. Bullies are often impulsive and aggressive toward their environment [1, 40]. They often show other problem behavior as well, as expressed in higher prevalences of conduct disorder [1, 2]. It is possible that they are more sensitive to developing psychotic phenomena, like subclinical psychotic experiences, than non-involved children, as patterns of antisocial behavior in childhood and early adolescence have been observed prior to the onset of schizophrenia [20, 25]. Victims are often insecure, withdrawn and have a negative self-image [1]. Previous research showed that psychotic experiences such as hallucinations and delusions are associated with a low selfesteem [4] and paranoia with negative interpersonal beliefs, which are associated with previous (negative) interpersonal experiences [6, 7, 26]. Although the mentioned studies focused on family relations, bullying can also be seen as a negative interpersonal experience. Paranoid delusions have been described as an extreme method to maintain selfesteem in individuals with a low self-esteem [6]. Bullyvictims are seen as the most troubled. They are aggressive, like bullies, but also have internalizing problems and a negative self-image, like victims [40]. Their personality appears to be the most disturbed, because they have got contradictory meanings about themselves. They feel powerful but at the same time mention numerous negative characteristics [22]. In a study of Mynard and Joseph [34] who studied the association of personality dimensions with
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bullying, bully-victims differed from both bullies and victims on some dimensions as social acceptance and neuroticism, but in general were seen as closer reminiscent of bullies than victims. Like bullies, it is also possible for bully-victims that they are more sensitive to developing psychotic phenomena, like subclinical psychotic experiences, than non-involved children. The bully climate of a classroom can moderate the effect of bullying on subclinical psychotic experiences, in particular of victims. Our study showed that the higher the bully climate, the less subclinical psychotic experiences were associated with being bullied (b = -0.004). It could be hypothesized that in these classes victims find more support from other victims, which may buffer the negative effect of bullying on their psychological functioning. Victims may reach out for each other and get support from the fact that they are not the only ones who are being bullied. This is in line with the ethnic or group density hypothesis. Support for this hypothesis is found by Nishina and Juvonen [35] who found that victims of bullying reported higher levels of anxiety and had a lower self-esteem than children who were not bullied. However, when they witnessed someone else being bullied, they felt less anxious and had a higher self-esteem on days when they were bullied themselves. They only felt humiliated and angry when they saw themselves as lone targets. Some victims blame themselves for being bullied [18]. Witnessing someone else being bullied in a classroom could also reduce their thoughts of self-blame: ‘‘it’s not only me, so i’m not the one to blame’’. This could also partly explain the fact that the interaction with bully climate is only found for victims and not for bullies and bully-victims. Victims are personally affected when they are being bullied, as some of them tend to blame themselves for it. The more other kids are being bullied, the less they need to blame themselves [18] and thus the less it may personally affect them. Another explanation is more focused on bullying as a group phenomenon. Sentse et al. [39] conducted a study on the effect of bullying in a classroom on peer preference. It showed that in a classroom where bullying is non-normative (there are not many victims), both victims and bullies are rejected by the group. In a classroom where bullying is normative (there are many victims), victims are still rejected by their classmates (although slightly less than in a classroom where bullying is non-normative), while bullies are more preferred by their classmates. Thus, the average behavior of classmates determines whether you will be accepted in a classroom or not.
Implications First of all, it is important to point out that bullying cannot be justified and should always be prevented. Although a
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high amount of bullying in classes seems to benefit the victims, the average score on subclinical psychotic experiences, even in classes where bullying is more common, is still higher in involved than in non-involved children. Both teachers and students should be aware of the (long-term) effect of bullying on the mental health of victims. Our results suggest that it is important for victims in classes where bullying is not quite common, to get into contact with co-victims. This could give them some support. Subsequently, knowing they are not the only ones could reduce their thoughts of self-blame, negative selfimage, and low self-esteem, which could reduce their paranoid delusions (their extreme method to maintain selfesteem).
Limitations A number of limitations of this study need to be mentioned. The first limitation concerns the measurement of bullying and subclinical psychotic experiences. Bullying and subclinical psychotic experiences are measured by self-report, which can lead to incorrect or social desirable answers. A second limitation is the fact that the data are cross-sectional and therefore we cannot disentangle the temporal relationship between subclinical psychotic experiences and bully climate and no inferences can be made on causality. Furthermore, those who were excluded from the analyses because of missing items on the CAPE, differed from those included in the analyses on a number of characteristics (e.g., excluded cases were more often bully-victims and more often attended classes with a high bully climate). Therefore, we may have underestimated the strength of the relationship between bullying and subclinical psychotic experiences. The prevalence of bullying types was rather low, with small percentage of students being bully-victim. Lack of power may explain the fact that we only found significant interactions between bullying climate and being a victim. A final limitation is that the questions about bullying are asked about the school (and not specifically the class), so it is not clear whether the victims stay in the same class as their bullies or not. On the other hand, students in the same class are together more often and it is likely that reported bullying takes place in this context. Conflict of interest On behalf of all authors, the corresponding author states that there is no conflict of interest.
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