School Bullying and Mental Health in Children and Adolescents

Overview Taiwanese Journal of Psychiatry (Taipei) Vol. 24 No. 1 2010 3 School Bullying and Mental Health in Children and Adolescents Cheng-Fang Yen, M.D., Ph.D. 1,2 Bullying is a malicious aggressive behavior that is intended to harm others repeatedly. There is an imbalance in strength or power between the bullies and the victims of bullying. Studies in European countries and U.S. suggest that 20% to 30% of students are frequently involved in bullying as bullies and/or victims. Cross-sectional and longitudinal studies have recognized bullying and being victimized by bullies as health problems for school children and adolescents because of their association with a range of adjustment problems, including poor mental health and violent behavior. Bully-victims, who are involved in both bullying others and being bullied by others, have the greatest number of mental and behavioral problems. Children needing special health care are especially vulnerable to being bullied. The significant association between involvement in bullying and adverse mental health in children and adolescents indicates that the early identification of and intervention on children and adolescents at risk should be a priority for the society. Key words: Bully, mental health, school health (Taiwanese Journal of Psychiatry [Taipei] 2010;24:3-13 ) Introduction While the investigation of school bullying is a relatively recent phenomenon in Taiwan, it has been thoroughly investigated in several countries. Scandinavian countries initiated the early research regarding school bullying [1] and researchers from other countries followed their lead. Unfortunately, the attention to the issue of school bullying often follows the misery happened. For example, the horrendous shootings at Columbine High School in 1999 have fueled a national concern over peer-bullying and victimization [2]. Students involved in school shootings have been characterized as chronic bullying victims who in turn have victimized their peers [3]. Researchers studying school associated violent deaths between 1994 and 1999 found that homicide perpetrators were more likely than their victims to have been bullied at school [4]. Bullying and being victimized by bullies have been recognized as health problems for school children and adolescents because of their association with a range of adjustment problems, including poor mental health and violent behavior Department of Psychiatry, 1 Faculty of Medicine, College of Medicine, and 2 Kaohsiung Medical University Hospital, Kaohsiung Medical University, Taiwan. Received: August 1, 2008 Address correspondence to: Dr. Cheng-Fang Yen, Department of Psychiatry, Kaohsiung Medical University, No. 100, Tzyou 1st Road, Kaohsiung 807, Taiwan

4 Bullying and Mental Health [5]. Being bullied is one of the most distressing experiences for a child or adolescent, especially when it occurs over a prolonged period of time [6]. It is necessary for psychiatrists, pediatricians, school psychologists, educators and parents to increase knowledge about school bullying and victims in children and adolescents. Definition Bullying is an aggressive behavior characterized by three defining conditions: (a) negative or malicious behavior intended to harm or distress, (b) behavior repeated over a time period, and (c) a relationship in which there is an imbalance in strength or power between the parties involved [7, 8]. Thus, fighting between two persons of similar strength and skill would not be defined as bullying. Bullying behavior can be physical acts (hitting, pushing, and kicking), verbal utterances (name calling, provoking, making threats, and spreading rumors), or other behaviors (making faces or social exclusion) [9]. Bullying takes place within relatively small and stable settings (like classes), which are characterized by the presence of the same people (e.g., children) [10]. Four groups have been distinguished: pure bullies, those who bully other children only; pure victims, who are children who are victimized by bullies; bully-victims, who are children who are involved in bullying other children and who also are victims of bullying, and neutral children [11, 12]. The study on the trajectory found that the bully-victims had been bullied for the most part during an earlier time period than they bullied others; some were bullies and victims during the same period; and very few bullied others before being a victim of bullying [13]. Generally, children other than the bullies and their victims are also involved in the bullying process and may actually maintain the bullying by supporting the bully or failing to defend the victim. Salmivalli and colleagues [14] suggested that all the children in a particular class play a role in bullying and that only few of them may be considered to be uninvolved. The Prevalence Large studies in European countries and U.S. suggest that 20% to 30% of students are frequently involved in bullying as perpetrators and/or victims [7,15-18]. For example, in a nationally representative study of 6th to 10 th grade US students (n = 15,686), 13% were identified as bullies, 11% as victims, and 6% as bully-victims [7]. However, the prevalence of bullying involvement could be various across different countries and studies. For example, in a cross-national study of 113,200 students between the ages of 11 and 15 from 25 countries found that involvement in bullying varied dramatically across countries, ranging from 9% to 54% of youth [19]. A study on 5,074 adolescent school children in grade 8 (mean age 14.2 years) and grade 11 (mean age 17.4 years) in South Africa found that over a third (36.3%) of students were involved in bullying behavior, 8.2% as bullies, 19.3% as victims and 8.7% as bullyvictims [20]. A study on 1,756 Korean middle school students found that 40% of all children participated in school bullying, 17% as bullies, 14% victims, and 9% bully-victims [21]. Except for variations in social background and culture, several possible explanations for the variations in the prevalence of school bullying have been found in previous studies. School children and adolescents with difference socio-demographic characteristics may have different prevalence of bullying involvement (discussed below).

Yen CF 5 Meanwhile, prevalence of bullying depends highly on the behaviors studied and how questions about bullying are posed. Several methods have been used in school bullying research: self-report, peer nomination and teachers and parents observation. Self-report has most commonly been used and has advantages by providing direct access to the feelings and experiences of children involved in bullying. This is particularly useful because the children are alert to the possibility of peer abuse, have strong emotional reactions to such events, and develop vivid and lasting memories of such experiences [22]. Peer nomination allows for assessment of an individual s behaviors by peers who are most likely to have witnessed or participated in these behaviors. Meanwhile, it permits the aggregation of peer/classmate judgment about individuals roles in school bullying [21]. Teachers and parents observations have also been frequently used to represent the conditions of bullying activities in school children and adolescents. However, several studies have indicated that many students do not agree with the view of adults and researchers as the specific types of behaviors that should be regarded as bullying [23]. Meanwhile, a subset of relational type behaviors (e. g., spreading rumors, social exclusion) is covert and has recently been shown to be harder to be detected by both teachers and parents [24, 25]. Children are less likely to report incidents of relational aggression when compared with direct physical or direct verbal incidents [26]. Even the studies applying self-report to detect the prevalence of school bullying involvement varied in the contents of questions and definition: while some studies used simple one or two questions to inquire participants experiences of bullying or victimization [27, 28], other studies used multi-dimensional questionnaires to measure bully/victim problems [29, 30]. Readers should take these differences in methods to detect bullying involvement into consideration when comparing the various results of studies. Demographic Correlates Several researchers have found that boys are more often involved in bullying than girls, both as bullies and victims [20, 31, 32]. However, although boys engage in more physical aggression and bullying, the sex difference is less pronounced for verbal bullying and is sometimes the reverse for indirect bullying [33]. Bulling by physical acts is, however, less common among girls; girls typically use more subtle and indirect ways of harassment such as slandering, spreading rumors, intentionally excluding someone from the group, and manipulating friendship relations [13, 34]. Several studies have found that both bullying and being bullied tend to be more common among younger students than older ones [7, 29, 35]. But two UK studies did not find any age effect [36, 37]. According to the developmental theory of aggression of Björkqvist et al. [38], younger age groups tend to use direct (particularly physical and psychological or verbal) types of aggression more because their social skills have not developed sufficiently to use more subtle forms of aggression (such as gossiping, ostracising and spreading rumors). Victimization is more frequent in younger age groups [33]. The odds of being a victim (vs. a neutral child) were 10% lower for every 1 point increase in grade point average [39]. Accordingly, Olweus [32] found that more than 50% of bullied children in the lowest grades (8- and 9-year-olds) reported that older students bullied them. From a developmental perspective for the vulnerability to being victimized in younger children, Smith and colleagues in 1999 gave two explanations: First, younger children in school have more older chil-

6 Bullying and Mental Health dren who can bully them. Second, younger children have not yet acquired the social skills to deal effectively with bullying incidents [40]. But in a Finnish cohort, bullying and being bullied are found to be rather stable between the ages of 8 and 16 years: almost all boys who were bullied at the age of 16 years had been bullied already at age of 8 years, and half of them who bullied at 16 years of age had already been bullying when they were 8 years of age. [18]. Involvement in Bullying and Mental Health Victims of bullying Children and adolescents who are bullied have been found to have both physical health problems [19, 41, 42] and mental health problems, such as depression [19, 26, 29, 42], anxiety [16, 44], suicide ideation [45], hyperactivity [46], and conduct problems [46] and physical health problems. The effects of bullying on emotional health may persist over time. For example, children who were bullied repeatedly through middle adolescence were found to have lower self-esteem and more depressive symptoms after they grew up [47]. Girls who were bullied tended to have eating disorders [16]. Victims have also been found to show various social difficulties [15, 46, 48, 49], such as high levels of social anxiety [50, 51], loneliness [47], avoidance of social situations [52] and social skills deficits [53]. Both chronic adversities and failure to receive support from the social network might increase the risk of depression. The learned helplessness theory may be used to explain why some victimized youth experience internalizing symptomology [54]. On the other hand, it has been reported that internalizing problems contributed to becoming a victim, which again increased later internalizing symptoms [50]. The direction of causality between victimization and mental health complaints can thus be both ways [16]. Meanwhile, peer rejection and peer abuse that are inherent to school bullying may have a direct effect to cause suicidal ideation and suicidal behaviors in children and adolescents [29]. Researchers also found that violent and antisocial behaviors were increased in victims of bullying [20]. One could speculate that the increased levels of violence in victims may be due to their victimization and/or subsequent need for self-defense. Contrariously, the increased level of violence in victims can produce both anxious and aggressive reaction patterns in the subset of vulnerable victims [32]. Increased levels of theft in victims may be in response to extortion from bullies (e.g., stealing from home to pay off bullies). Or it may be a form of comfort stealing or attention-seeking as a response to the distress of victimization [20]. Although some research were found that low self-esteem is not associated with victimization when the effects of anxiety and depression have been controlled for [44], the results of most of studies generally indicate that low self-esteem or low global self-worth is associated with repeated victimizations [47, 48, 50]. Low self-esteem has also been found to mediate the linkages of victimization with emotional problems for girls [55]. Bullies Bullying is associated with violent behaviors [56], hyperactivity [41, 46, 57] and school problems [58, 59]. Some research have shown that the aggression displayed by bullies is likely to reflect a controlled behavior that is oriented toward achieving instrumental outcomes [60, 61]. Bullies engage in high rates of interpersonal power dominance and instrumental aggression such as coerc-

Yen CF 7 ing others to give them their property. Longitudinal studies show that this type of behavior pattern, i. e., externalizing problems, is relatively stable over time. Aggressive trajectories are associated with subsequent antisocial and criminal behavior in adolescence [62]. Age at onset and level or form of aggression have become important factors in understanding antisocial development [63], because early onset of antisocial behavior is regarded as a reliable predictor of adult antisociality [64]. Bullies have been found to have higher risk for health problems [19] and social adjustment [19]. Among girls, eating disorders were associated with bullying [16]. Children who habitually bully are significantly more likely to experience high levels of depression [19, 26, 44] and suicidal ideation [65]. Another study showed that the association between bullying and suicidal ideation exist in boys [65]. The relatively high levels of suicidal ideation of male bullies are possibly related to generally high levels of aggressiveness. This explanation may be based on psychological effects of having engaged repeatedly in unjustifiable acts of aggressiveness against less powerful individuals [65]. Furthermore, the association is also possibly related to negative styles of parenting commonly experienced by children who bully [66]. Whether bullies have low self-esteem is still a disputed issue [34, 67, 68]. Bully-victims Previous studies found that compared with the pure bullies and victims, the bully-victims have the greatest number of problems including (a) externalizing behavior, hyperactivity, and conduct disorder [41, 69], and the highest risk of weapon carrying [19]; (b) concurrent and future psychological and psychosomatic symptoms [15-17, 70,]; (c) referrals to psychiatric services [71]; (d) the highest probability of persistence of involvement in bullying [71]; (e) the highest relative risk of suicidal ideation [43]; (f) the poorest school and interpersonal function [11, 19, 41, 72-74]; (g) the highest relative risk of alcohol use [19]; and (h) the most physical injuries [2, 74]. Meanwhile, boy bully-victims tend to have eating disorders [16]. This group may be at greatest risk of developing psychopathology [73, 75]. These findings suggest that bully-victims may be a distinct group of the most troubled among all students involved with bullying. Thus, it has been proposed that bully-victims could benefit from early identification and intervention in particular [76]. Some researchers failed to differentiate the bully-victims from the bullies and victims. For example, the study of Liang and colleagues [20] showed that the bully-victims level of fighting, weapon-carrying, theft, and risk-taking behaviors do not significantly exceed those of the bullying group, and that their increased suicidal ideation is similar to that in the victim group. These findings suggest that bully-victims constitute an overlap between bully and victim categories, and that an elevated risk exists for the negative outcomes of both groups [20]. In contrast to the aggression displayed by bullies, bully-victims are likely to have a controlled behavior which is oriented toward achieving instrumental outcomes [60, 61]. Often, bullyvictims aggression is reflecting an underlying state of poorly modulated anger and irritability [77]. Results of longitudinal studies The association between school bullying and psychopathologic behavior has been extensively debated with two 2 causal hypotheses [75]: (A) antecedent psychopathologic behavior is a cause

8 Bullying and Mental Health of subsequent bullying, and (B) bullying can lead to future psychopathologic behaviors. The first hypothesis was supported by previous findings showing that children with internalizing or externalizing problems have a higher risk of involvement with bullying [48, 50]. The second hypothesis was supported by previous reports of deteriorating behavioral, emotional, and psychosocial functioning in children who experienced peer victimization [32, 78, 79]. This debate is unresolved because cross-sectional research designs have made it impossible to establish causality in either direction [75]. Only longitudinal studies can provide data to clarify the causality of direction. Table 1 lists the results of several large-scale, longitudinal studies on the associations between involvement in bullying and mental health. The results of longitudinal studies suggest that involvement in bullying in children and adolescents is a risk factor for subsequent mental health and conduct problems. Table 1. The results of large-scale, longitudinal studies on the associations between involvement in bullying and mental health Authors Sample Follow-up period Arseneault et al., 2006 Bond et al., 2001 Kim et al., 2006 Kumpulainen et al., 2000 Sourander et al., 2007a Sourander et al., 2007b 2,232 US children at the age of 5 years 2,680 Australian adolescents at the age of 13 years 1,655 Korean seventh and eighth-grade students 1,316 Finnish children at the age of 8.5 years 2551 Finnish boys at the age of 8 years 2,540 Finnish boys at the age of 8 years Results 2 years Pure victims and bully/victims showed more behavior and school adjustment problems at 7 years of age after controlling for preexisting adjustment problems at 5 years of age. 1 year Victimization at age 13 predicted the onset of self-reported symptoms of anxiety and depression 1 year later. 10 months Victims at baseline showed increased risk of social problems. Bullies had increased aggression. Bully-victims had increased aggression and externalizing problems. Wave 1: 8.5 year old; Wave 2: 12.5 years old; Wave 3: 15.5 years old Children involved in bullying, in particular those who were bully-victims at the age of 8.5 years and those who were victims at the age of 12.5 years had more psychiatric symptoms at the age of 15.5 years. The probability of being deviant at the age of 15.5 years was higher among children involved in bullying at the age of 8.5 or 12.5 years than among noninvolved children. 8 to 12 years Frequent pure bullying predicted both occasional and repeated offending, whereas bully-victimization predicted repeated offending. Bullying predicted most types of crime when controlled with parental education level. Frequent bullies or victims without a high level of psychiatric symptoms were not at an elevated risk for later criminality. 10 to 15 years Frequent pure victimization predicted anxiety disorders, and frequent pure bullying predicted antisocial personality disorder, whereas frequent bully-victimization predicted both anxiety and antisocial personality disorder.

Yen CF 9 Involvement in Bullying among Children with Special Health Care Needs A study on the attributions of getting bullied in a sample of 10-year-old children found that the most common characteristic was that the victims have a different appearance [80]. Another study also found that children thought that other children get bullied because they were small, weak, and soft [81]. Those study results indicate that children needing special health care may be more vulnerable to being bullied. The National Survey of Children s Health on 102,000 US households found that being a child needing special health care is associated with being bullied [82]. Previous studies found that children with learning difficulties [83], autism [84, 85] and intellectual disability [86] are more likely to be bullied than those in general children population. Contrariwise, the National Survey of Children s Health also showed that a child having a chronic behavioral, emotional, or developmental problem is associated with bullying others and with being a bully/victim [82]. While children with autism but without attentiondeficit/hyperactivity disorder (ADHD) are not at greater risk for bullying, children with both autism and ADHD have increased odds of bullying others [87]. Those findings may help mental health providers, pediatricians, and schools use targeted screening and interventions to address bullying for children with special health care needs [82]. Clinical implication The significant association between involvement in bullying and adverse mental health in children and adolescents mentioned above indicates that the early identification of those at risk should be a priority for the society. All mental health workers, educators, pediatricians, and family physicians have a pivotal opportunity to screen, identify, and prevent school bullying and adverse mental health in children and adolescents [29]. Although bullying is probably referred for psychiatric consultation [41], many bullies and victims had no contact with the child mental health services. Identifying the bullies and victims is the fist step to assess and to intervene in their mental health problems. On the other hand, an approach to screening that relies first on identifying bullies, victims, or bully-victims, and then conducts a psychiatric screening could be a cost-effective alternative to universal screening of all children for psychiatric problems, especially when child mental health resources are scarce. However, the screening approach requires second-stage clinical evaluations, effectively functioning child mental health services, and efforts to assist families in obtaining help [73]. Additional studies that address the prevalence of involvement in bullying, their negative impacts on mental health, and resilience factors (e. g., parental and social support systems and the child s cognitive and social skills in dealing with bullying behavior) among children and adolescents in Taiwan are warranted. References 1. Olweus D: Aggression in the Schools: Bullying and Whipping Boys. Washington, DC: Hemisphere, 1978. 2. Stein JA, Dukes RL, Warren JI: Adolescent male bullies, victims, and bully-victims: a comparison of psychosocial and behavioral characteristics. J Pediatr Psychol 2007;2:273-82. 3. Unnever JD: Bullies, aggressive victims, and victims: Are they distinct groups? Aggress Behav 2005;31:153-71. 4. Anderson M, Kaufman J, Simon TR, et al.: Schoolassociated violent deaths in the United States, 1994-1999. JAMA 2001;286:2695-702.

10 Bullying and Mental Health 5. Spivak H, Prothrow-Stith D: The need to address bullying an important component of violence prevention. JAMA 2001;285:2131-2. 6. Whitney I, Nabuzoka D, Smith PK: Bullying in schools: mainstream and special needs. Support for Learning 1992;7:3-7. 7. Nansel TR, Overpeck MO, Pilla RS, Ruan WJ, Simons-Morton B, Scheidt P: Bullying behaviors among U.S. youth: prevalence and association with psychosocial adjustment. JAMA 2001;16: 2094-100. 8. Olweus D: Bullying at School: What We Know and What We Can Do. Oxford, United Kingdom: Blackwell Publishers, 1993. 9. Wolke D,Woods S, Bloomfield L, Karstadt L: The association between direct and relational bullying and behaviour problems among primary school children. J Child Psychol Psychiatry 2000;41:989-1002. 10. Camodeca M, Goossens FA: Aggression, social cognitions, anger and sadness in bullies and victims. J Child Psychol Psychiatry 2005;46:186-97. 11. Schwartz D: Subtypes of victims and aggressors in children s peer groups. J Abnorm Child Psychol 2000;28:181-92. 12. Woods S, White E: The association between bullying behaviour, arousal levels and behaviour problems. J Adolesc 2005;28:381-95. 13. Frisén A, Jonsson AK, Persson C: Adolescents perception of bullying: who is the victim? Who is the bully? what can be done to stop bullying? Adolescence 2007;42:749-61. 14. Salmivalli C, Lagerspetz K, Björkqvist K, Österman K, Kaukiainen A: Bullying as a group process: participant roles and their relations to social status within the group. Aggress Behav 1996;22:1-15. 15. Forero R, McLellan L, Rissel C, Bauman A: Bullying behaviour and psychosocial health among school students in New South Wales, Australia: cross sectional survey. Br Med J 1999; 319:344-48. 16. Kaltiala-Heino R, Rimpelä M, Rantanen P, Rimpelä A: Bullying at school an indicator of adolescents at risk for mental disorders. J Adolesc 2000;23:661-74. 17. Kumpulainen K, Räsänen E: Children involved in bullying at elementary school age: their psychiatric symptoms and deviance in adolescence. An epidemiological sample. Child Abuse Negl 2000;24:1567-77. 18. Sourander A, Helstelä L, Helenius H, Piha J: Persistence of bullying from childhood to adolescence: a longitudinal 8-year follow-up study. Child Abuse Negl 2000;24:873-81. 19. Nansel TR, Craig W, Overpeck MD, Saluja G, Ruan WJ: Health Behaviour in School-aged Children Bullying Analyses Working Group. Cross-national consistency in the relationship between bullying behaviors and psychosocial adjustment. Arch Pediatr Adolesc Med 2004;158:730-6. 20. Liang H, Flisher AJ, Lombard CJ: Bullying, violence, and risk behavior in South African school students. Child Abuse Negl 2007;31:161-71. 21. Kim YS, Koh YJ, Leventhal BL: Prevalence of school bullying in Korean middle school students. Arch Pediatr Adolesc Med 2004;158:737-41. 22. Ladd GW, Kochenderfer-Ladd BJ: Identifying victims of peer aggression from early to middle childhood: analysis of cross-informant data for concordance, estimation of relational adjustment, prevalence of victimization, and characteristics of identified victims. Psychol Assess 2002;14:74-96. 23. Boulton MJ, Bucci E, Hawker DDS: Swedish and English secondary school pupils attitudes towards, and conceptions of, bullying: concurrent links with bully/victim involvement. Scand J Psychol 1999;40: 277-87. 24. Magdol L, Moffitt TE, Caspi A, Newman DL, Fagan J, Silva PA: Gender differences in partner violence in a birth cohort of 21-year-olds: bridging the gap between clinical and epidemiological approaches. J Consult Clin Psychol 1997;65:68-78. 25. Rivers I, Smith PK: Types of bullying behaviour and their correlates. Aggress Behav 1994;20:359-68. 26. Seals D, Young J: Bullying and victimization: prevalence and relationship to gender, grade level, ethnicity, self-esteem, and depression. Adolescence 2003;38: 735-47. 27. Ball HA, Arseneault L, Taylor A, Maughan B, Caspi A, Moffitt TE: Genetic and environmental influences on victims, bullies and bully-victims in childhood. J

Yen CF 11 Child Psychol Psychiatry 2008;49:104-12. 28. Janssen I, Craig WM, Boyce WF, Pickett W: Associations between overweight and obesity with bullying behaviors in school-aged children. Pediatrics 2004;113:187-94. 29. Carlyle KE, Steinman KJ: Demographic differences in the prevalence, co-occurrence, and correlates of adolescent bullying at school. J Sch Health 2007;77: 623-9. 30. Kyriakides L, Kaloyirou C, Lindsay G: An analysis of the Revised Olweus Bully/victim Questionnaire using the Rasch measurement model. Br J Educ Psychol 2006;76:781-801. 31. Glew GM, Fan MY, Katon W, Rivara FP, Kernic MA: Bullying, psychosocial adjustment, and academic performance in elementary school. Arch Pediatr Adolesc Med 2005;15:1026-31. 32. Olweus D: Bullying at school: long-terms outcomes for the victims and an effective school-based intervention program. In: Aggressive Behavior: Current Perspectives. Ann Arbor: University of Michigan, 1994:97-130. 33. Smith PK: Bullying: Recent developments. Child Adoles Ment Health 2004;9:98-103. 34. Olweus D: Bully/victim problems in school: facts and interventions. Eur J Psychol Educ 1997;12: 495-510. 35. Olweus D: Bully/victim problems among school children: Basic facts and effects of a school based intervention programme. In: Pepler D, Rubin K, eds. The Development and Treatment of Childhood Aggression. Hillsdale, NJ: Lawrence Erlbaum, 1991. 36. Smith P: The silent nightmare: bullying and victimization in school peer groups. Psychologist 1991;4: 243-8. 37. Johnson HR, Thompson MJJ, Wilkinson S, Walsh L, Balding J, Wright V: Vulnerability to bullying: teacher-reported conduct and emotional problems, hyperactivity, peer relationship difficulties and prosocial behaviour in primary school children. Educ Psychol 2002;22:553-6. 38. Björkqvist K, Osterman K, Kaukiainen A: The development of direct and indirect aggressive strategies in males and females. In: Of Mice and Women: Aspects of Female Aggression, Björkqvist K, Niemela P, eds. San Diego, CA: Academic Press, 1992. 39. Glew GM, Fan MY, Katon W, Rivara FP: Bullying and school safety. J Pediatr 2008;152:123-8. 40. Smith PK, Madsen KC, Moody JC: What causes the age decline in reports of being bullied at school? towards a developmental analysis of risks of being bullied. Educ Res 1999;41:267-85. 41. Kumpulainen K, Räsänen E, Henttonen I et al: Bullying and psychiatric symptoms among elementary school-age children. Child Abuse Negl 1998;22: 705-17. 42. Williams K, Chambers M, Logan S, Robinson D: Association of common health symptoms with bullying in primary school children. Br Med J 1996;313: 17-9. 43. Kaltialo-Heino R, Rimpelä M, Marttunen M, Rimpelä A, Ratenen P: Bullying, depression and suicidal ideation in Finnish adolescents: school survey. BMJ 1999;319:348-50. 44. Salmon G, Jones A, Smith DM: Bullying in school: self-reported anxiety and self-esteem in secondary school children. BMJ 1998;317:924-5. 45. Kim YS, Koh YJ, Leventhal B: School bullying and suicidal risk in Korean middle school students. Pediatrics 2005;115:357-63. 46. Gini G: Associations between bullying behaviour, psychosomatic complaints, emotional and behavioural problems. J Paediatr Child Health, 2007 (in press). 47. Olweus D: Victimization by peers: antecedents and long-term outcomes. In: Rubin K, Asendorf JB, eds. Social Withdrawal, Inhibition, and Shyness in Children. Hillsdale, NJ: Lawrence Erlbaum Associates, 1993:315-41. 48. Boulton MJ, Smith PK: Bully/victim problems in middle-school children: stability, self-perceived competence, peer perceptions and peer acceptance. Br J Dev Psychol 1994;12:315-29. 49. Crick NR, Bigbee MA: Relational and overt forms of peer victimization: a multiinformant approach. J Consult Clin Psychol 1998;66:337-47.

12 Bullying and Mental Health 50. Hodges E, Perry D: Personal and interpersonal antecedents and consequences of victimization by peers. J Pers Soc Psychol 1999;76:677-85. 51. Walter KS, Inderbitzen HM: Social anxiety and peer relations among adolescents: testing a psychobiological model. J Anxiety Disord 1998;12:183-98. 52. Storch EA, Masia-Warner CL: The relationship of peer victimization to social anxiety and loneliness in adolescent females. J Adolesc 2004;27:351-62. 53. Schwartz D, Dodge KA, Coie JD: The emergence of chronic peer victimization in boys play groups. Child Dev 1993;64:1755-72. 54. Swearer SM, Grills AE, Haye KM, Cary PT: Internalizing problems in students involved in bullying and victimization: implications for intervention. In: Espelage DL, Swearer SM, eds. Bullying in American Schools: A Social-ecological Perspective on Prevention and Intervention. Mahwah, NJ: Lawrence Erlbaum Associates, 2004:63-83. 55. Lopez C, Dubois DL: Peer victimization and rejection: investigation of an integrative model of effects on emotional, behavioral, and academic adjustment in early adolescence. J Clin Child Adolesc Psychol 2005;34:25-36. 56. Nansel TR, Overpeck MD, Haynie DL, Ruan WJ, Scheidt P: Relationships between bullying and violence among US youth. Arch Pediatr Adolesc Med 2003;157:348-53. 57. Rigby K, Slee PT: Dimensions of interpersonal relation among Australian children and implications for psychological well-being. J Soc Psychol 1993;133: 33-42. 58. Loeber R, Dishion TJ: Early predictors of male delinquency: a review. Psychol Bull 1983;94:68-99. 59. Slee PT, Rigby K: Australian school children s self appraisal of interpersonal relations: the bullying experience. Child Psychiatry Hum Dev 1993;23:273-82. 60. Crick NR, Dodge KA: Social information-processing mechanisms in reactive and proactive aggression. Child Dev 1996;67:993-1002. 61. Dodge KA, Coie JD: Social-information-processing factors in reactive and proactive aggression in children s peer group. J Pers Soc Psychol 1987;53: 1146-58. 62. Nagin D, Tremblay RE: Trajectories of boys physical aggression, opposition, and hyperactivity on the path to physically violent and nonviolent juvenile delinquency. Child Dev 1999;70:1181-96. 63. Sourander A, Jensen P, Rönning JA et al: Childhood bullies and victims and their risk of criminality in late adolescence: the Finnish From a Boy to a Man study. Arch Pediatr Adolesc Med 2007;161:546-52. 64. Moffitt TE, Caspi A, Harrington H, Milne BJ: Males on the life-course-persistent and adolescence-limited antisocial pathways: follow-up at age 26 years. Dev Psychopathol 2002;14:179-207. 65. Rigby K, Slee PT: Suicidal ideation among adolescent school children, involvement in bully victim problems and perceived low social support. Suicide Life Threat Behav 1999;29:119-30. 66. Rigby K: Psycho-social functioning in families of Australian adolescent school-children involved in bully victim problems. J Fam Ther 1994;16:173-89. 67. O Moore M: Critical issues for teacher training to counter bullying and victimization in Ireland. Aggress Behav 2000;26:99-111. 68. Kaukiainen A, Salmivalli C, Lagerspetz K, et al.: Learning difficulties, social intelligence, and selfconcept: connections to bully-victim problems. Scand J Psychol 2002;43:269-78. 69. Kokkinos CM, Panayiotou G: Predicting bullying and victimization among early adolescents: Associations with disruptive behavior disorders. aggress Behav 2004;30:520-33. 70. Fekkes M, Pijpers FIM, Verloove-Vanhorick SP: Bullying behavior and associations with psychosomatic complaints and depression in victims. J Pediatr 2004;144:17-22. 71. Kumpulainen K, Rasanen E, Henttonen I: Children involved in bullying: psychological disturbance and the persistence of the involvement. Child Abuse Negl 1999;23:1253-62. 72. Juvonen J, Graham S, Schuster MA: Bullying among young adolescents: the strong, the weak, and the troubled. Pediatrics 2003;112:1231-7. 73. Sourander A, Jensen P, Rönning JA et al: What is the

Yen CF 13 early adulthood outcome of boys who bully or are bullied in childhood? The Finnish From a Boy to a Man study. Pediatrics 2007;120:397-404. 74. Veenstra R, Lindenberg S, Oldehinkel AJ, De Winter AF, Verhulst FC, Ormel J: Bullying and victimization in elementary schools: a comparison of bullies, victims, bully/victims, and uninvolved preadolescents. Dev Psychol 2005;41:672-82. 75. Kim YS, Leventhal BL, Koh YJ, Hubbard A, Boyce AT: School bullying and youth violence: causes or consequences of psychopathology? Arch Gen Psychiatry 2006;63:1035-41. 76. Arseneault L, Walsh E, Trzesniewski K, Newcombe R, Caspi A, Moffitt TE: Bullying victimization uniquely contributes to adjustment problems in young children: a nationally representative cohort study. Pediatrics 2006;118:130-8. 77. Toblin RL, Schwartz D, Gorman AH, Abouezzeddine T: Social-cognitive and behavioral attributes of aggressive victims of bullying. J Appl Dev Psychol 2005;26:329-46. 78. Hanish LD, Guerra NG: A longitudinal analysis of patterns of adjustment following peer victimization. Dev Psychopathol 2002;14:69-89. 79. Ladd GW, Troop-Gordon W: The role of chronic peer difficulties in the development of children s psychological adjustment problems. Child Dev 2003;74: 1344-67. 80. Erling A, Hwang P: Swedish 10-year-old children s perceptions and experiences of bullying. J Sch Violence 2004;3:33-43. 81. Boulton MJ, Underwood K: Bully/victim problems among middle school children. Br J Educ Psychol 1992;62:73-87. 82. Van Cleave J, Davis MM: Bullying and peer victimization among children with special health care needs. Pediatrics 2006;118:e1212-9. 83. Nabuzoka D, Smith PK: Sociometric status and social behaviour of children with and without learning difficulties. J Child Psychol Psychiatry 1993;34: 1435-48. 84. Little L: Peer victimization of children with Asperger spectrum disorders. J Am Acad Child Adolesc Psychiatry 2001;40:995-6. 85. Marini Z, Fairbairn L, Zuber R: Peer harassment in individuals with developmental disabilities: towards the development of a multidimensional bullying identification model. Dev Disabilities Bull 2001;29: 170-95. 86. Whitney I, Smith PK, Thompson D: Bullying and children with special educational needs. In: Smith PK, Sharp S eds. School Bullying: Insight and Perspectives. Routledge, London, 1994:213-40. 87. Montes G, Halterman JS: Bullying among children with autism and the influence of comorbidity with ADHD: a population-based study. Ambul Pediatr 2007;7:253-7. 88. Bond L, Carlin JB, Thomas L, Rubin K, Patton G: Does bullying cause emotional problems? a prospective study of young teenagers. BMJ 2001;323:480-4.