Bullying has been conceptualised as a distinct type of aggression characterised by a multifaceted form of mistreatment seen mostly at schools and at work. The most widely employed definition of bullying emphasises persistent and repeated negative actions intended to intimidate or hurt a weaker person. Bullying includes acts of deliberate physical aggression (e.g. knocks, punches and kicks), verbal aggression (e.g. name calling and threats), relational aggression (e.g. social isolation and rumour spreading) and cyber aggression (e.g. text messaging and e-mailing hurtful messages or pictures) . The negative interaction must occur relatively often (roughly on a weekly basis) and over a prolonged period of time (often 6 months) . Given the seriousness of bullying, prevention of childhood and adolescent bullying has long been considered an important social and clinical problem.
The prevalence of bullying
The prevalence of bullying among adolescents varies across countries. In two large cross-national studies – The Health Behavior in School-aged Children Survey and the Global School-based Students Health Survey – totalling 218,104 students in 66 countries aged between 11 and 15 years, the average prevalence of bullying victimisation at least once during the past month was 32.1 % in the first study, and in second study, 37.4 % of participants reported that they had been bullied at least once within the past 2 months. However, in both studies, a large variation in prevalence was found across countries, from 6 to 41 % in the first study and from 9 to 54 % in the second . In spite of large differences in the prevalence of bullying, the results indicate that too many pupils suffer from being victims of aggressive acts intended to hurt them.
The consequences of being bullied
The consequences of childhood bullying victimization are serious. Both cross-sectional and longitudinal studies have found that being a victim of bullying is associated with long-term psychological problems, including loneliness, general and social anxiety, diminished self-esteem, increased depressive symptoms and more frequent use of pain medication [4–6]. Finally, being a victim of bullying is an important risk factor for suicidal behaviour in adolescence and early adulthood [7, 8]. A review based on 37 studies found that any kind of participation in bullying increased the risk of suicidal ideation and/or behaviour. The strongest risk was for victim-perpetrators . However, bullies also suffer because severe suicidal ideation has been found among both those who were bullied and among those who were bullies .
Not surprisingly, many antibullying programmes and interventions have been implemented in an attempt to reduce the prevalence of being bullied. Unfortunately, the success of intervention programmes to prevent or mitigate bullying in childhood and adolescence has been limited. A synthesis of the existing research on antibullying programmes concluded that the majority of programmes yielded no significant reductions in self-reported bullying, and therefore only cautious recommendations could be made .
Theoretical frame of reference
Given the limited efficacy of bullying intervention programmes, the purpose of the present study was to more closely investigate multiple risk factors for bullying. Identifying risk factors can provide a basis for designing intervention programmes to prevent or reduce bullying among children and adolescents.
Studies on bullying at schools have identified several risk factors such as gender, age and deviate appearance of the victim; personal characteristics such as low self-esteem and lack of adequate coping skills; social status among peers and socioeconomic status in society. However, bullying is a complex phenomenon, and there is no single explanation for why some children are bullied by others . Furthermore, bullying is conceptualised as a distinct type of aggressive behaviour, and psychological theories of aggression assert that the occurrence of aggression can seldom be reduced to one single factor but is more likely to be influenced by several factors simultaneously . Aggressions, like other forms of complex behaviour, stem from the interplay of a wide range of personal, situational and social factors. Therefore, aggressive behaviour such as bullying occurs as a result of interactions between the persons involved and factors in the social context that may either facilitate or mitigate the risk of such behaviour [12, 13]. Although a detailed discussion of the causes of aggression is beyond the scope of this paper, it is important to underline the complexity of the task of identifying risk factors that are relevant in understanding bullying at schools and workplaces.
Several risk factors for being bullying at schools have been identified (for a review see ), but most studies identifying risk factors for bullying have included only a limited number of risk factors in their statistical models. All the risk variables may be correlated with each other, but some may be more important than others in predicting bullying. Therefore, the present study will simultaneously examine several different risk factors in young people related to their individual and personal levels, social levels and socioeconomic levels in order to identify the most important risk factors for bullying at schools and workplaces. This knowledge may be important in order to prevent bullying.
Preventing bullying may be good for the bullied as well as for the bullies in term of the negative psychological outcomes for both parties.
Risk factors for bullying
Potential risk factors for bullying at the individual level include gender, age, physical appearance and health behaviour. Regarding gender, the results are inconsistent, and no substantial gender differences have been observed among adolescents in terms of the frequency of being bullied either at school or at work . With respect to age, results from both cross-sectional and longitudinal studies on bullying at schools show that the prevalence of bullying tends to fall with age during adolescence [15–17].
When teens are asked why some adolescents are bullied, a common response is the deviant appearance of the victim . Overweight and obesity have been found to be associated with an increased risk of being bullied in both cross-sectional studies and cohort studies [19–22]. Also, bullying has been found to be related to underweight in adolescents , and even short pupils are at greater risk of being bullied . Apparently, any deviance from the physical norm may increase the risk of being bullied. Being a smoker also has been found to increase the risk of being bullied, but the results of studies on the relation between smoking and bullying are inconsistent [25–27].
At the personal level, self-esteem has been found to be associated with bullying . Self-esteem refers to the global and evaluative view of oneself, and low self-esteem is associated with a variety of psychological dysfunctions, whereas high self-esteem is associated with social adeptness, leadership, higher levels of adjustment and good social skills. Therefore, because of poor social skills and low levels of adjustment, it seems plausible that low self-esteem may be a risk factor for being bullying. It is, however, unclear whether low self-esteem is a risk factor for bullying or a consequence of being bullied [29–31]. For instance, among 2326 Italian adolescents, Brighi et al.  found that low global self-esteem was a risk factor for victimisation, but on the other hand, another study found that victimisation was the most consistent predictor of low self-esteem . Thus, it is unclear whether low self-esteem is a risk factor for or a consequence of being bullied. Furthermore, most studies are cross-sectional in design, making causal interpretations difficult. In this study, self-esteem was conceptualised as a risk factor, because it is considered to be a general internal presentation of social acceptance and rejection and a measure of social functioning. Thus, low self-esteem could be a risk factor for being a target of bullying.
Studies have demonstrated associations between an increased risk of being bullied and conflicts with parents and being from a family characterised by a punitive, conflicting and nonsupportive parenting style [10, 32]. Additionally, victims’ homes have been found to be characterised by a higher level of criticism and fewer rules  and having authoritative parents who rarely value their children and tend not to give them the opportunity to speak up for themselves . Overly protective parenting style could be a risk factor for bullying as well because parents who are overly protective of their children and do not let them handle conflicts with peers by themselves may contribute to the causation of bullying [35, 36]. However, the causal direction is unclear because of the cross-sectional design of these studies, and protective parenting could also be an outcome of bullying.
One consequence of inadequate parenting style or poor family functioning may be children’s insufficient coping strategies. For instance, a study found a clear relation between perceived parenting practices and coping in offspring . These researchers found that parenting characterised by warmth and acceptance involved both a high degree of parental monitoring but also parental demands for age-appropriate behaviour. Thus, the child may learn that events are to some degree controllable. The result of the study was that the children of parents using an accepting and warm parenting style more often used problem-focused coping strategies than did children who reported that their parents used other rearing styles. Therefore, one of the consequences of inadequate parenting style or poor family functioning may be inadequate coping skills and lack of social skills needed in order to resolve conflicts in the peer group or with work colleagues due to lack of experience with conflict resolution in the family. Based on this background, we sought to examine whether poor family functioning and overprotective parents predict bullying later at school or work.
The associations between bullying and coping have been examined in several studies, and the results show that victims of bullying lack adaptive coping strategies and more often use avoidant coping or similar strategies that might be considered similar [10, 38, 39]. For instance, one study found that victims of bullying rarely asked for help or talked about what happened, but instead remained passive . Another study found a positive association between emotionally oriented coping strategies and victimisation . Thus, it seems relevant to study the association between coping and bullying.
Regarding coping strategies, it is important to include the victims’ appraisal of the bullying situation because appraisals, according to the transactional theory of stress, determine the coping response, and thus victims’ perceptions of control become important for the implementation of coping strategies .
The concept of sense of coherence brings the perception of control and manageability into consideration. The concept refers to the individual’s perception of comprehensibility, meaningfulness and manageability, the last referring to expectations about the availability of adequate resources to cope with stressors. Sense of coherence affects how individuals perceive the events that happen to them, as well as the extent to which they perceive these events as controllable. Persons with a strong sense of coherence are described as more resistant to stress and able to cope adaptively , and studies have found a direct effect of sense of coherence on stress . One study found that strong sense of coherence offered protective benefits to targets exposed to bullying , and another study found that employees with a low sense of coherence more often were subjected to violence . In the present study, we analysed whether a low sense of coherence is a risk factor for bullying.
In regard to the social context, bullying is related to social status in the group. Indicators of status are social preference, popularity, school performance and socioeconomic status. Research has found that low levels of social preference and low levels of perceived popularity are associated with an increased risk of being bullied [46, 47]. However, the cross-sectional nature of the studies cannot exclude the possibility that low social status may be an outcome and not a precursor of bullying, and therefore more longitudinal studies are needed. Furthermore, a meta-analysis concluded that bullied pupils were more likely to achieve lower grades than nonbullied pupils. Low grades may reflect interpersonal and social difficulties that may increase the risk of bullying. However, the cross-sectional nature of the studies cannot exclude that bullying may lead to mental distress, which could affect school performance . Although the negative relation between victimisation and academic performance is significant, there are few longitudinal studies on this topic. Thus, it is unclear whether victimisation can be conceptualised as a risk factor or an outcome of poor academic performance. In the present study, low social status and low school performance were conceptualised as risk factors for bullying; even though some longitudinal studies have shown that being a victim of bullying predicts later academic difficulties, there are only limited results supporting this notion .
Finally, the socioeconomic status in society is also related to bullying, and research has revealed that exposure to bullying is patterned by socioeconomic status because adolescents from lower socioeconomic status families are at higher risk of being bullied [50–53]
One explanation could be that inequalities in society may lead to more widespread approval of behaviours associated with social status differences such as bullying . Furthermore, growing up in a low social status family might be associated with more stress in the form of unemployment, divorce, illness and moving, which might affect children’s adaptive skills , again possibly increasing the risk of being bullied.
Stability of victimisation from bullying at school and at work
Given the negative consequences of bullying, it is important to examine the continuance continued risk of being bullied. In other words, is being bullied once a risk factor in itself for later victimisation?
Relatively little attention has been given to the effect of being bullied once on later victimisation, and the few studies that have examined the stability of victimisation from bullying during adolescence have found the risk of being bullied to be relatively stable. For instance, it was found that being a victim of bullying at age 8 was associated with victimisation 8 years later [8, 16]. So far only a few studies have differentiated between victimisation that continues from primary school to secondary school and from primary school to the workplace. Both at school and at work, environmental and organisational factors can be sources of bullying, so the stability of victimisation from primary school to the workplace would not necessarily be expected because environmental and organisational factors change. In spite of this, researchers have found that the highest risk factor for being bullied in the workplace was being a bully victim at school . This relationship was seen for both males and females. Furthermore, another study found that victims who are bullied at school report being bullied at work somewhat more often than do others . These results indicate that factors of continuity in the risk of victimisation could be more related to individual attributes such as low self-esteem, personality, lack of sufficient coping strategies and poor ability to establish protective social relationships than to environmental and organisational factors. While both studies were retrospective in design, which could have resulted in recall bias, the results indicate that being bullied once may be an important risk factor for being bullied later. In spite of the expansion of research on bullying victimisation, few studies have investigated possible links between individuals’ experience of previous victimisation at school and later victimisation at work or secondary school .
Research has revealed several different risk factors for being bullied at school.
Using data from a prospective cohort study of young people from the western part of Denmark, this study examines several risk factors for being bullied at 17–18 years of age, making it possible to test the independent contribution of each risk factor after adjustment for covariates in the same domain.
The purpose of the present study was to identify risk factors measured at age 14–15 for being bullied at age 17–18 at either work or school. Additionally, the study examines the associations between victimisation at the age of 14–15 years and victimisation later at the age of 17–18 years at a site of higher education or at work.
More specifically, the purposes of the study were as follows:
To examine the prevalence of being bullied at age 15 and at age 18 at work and at school
To identity the most important risk factors for being bullied at age 18, including the following:
Individual risk factors: gender, body mass index, smoking, previously being bullied at age 15
Personal risk factors: self-esteem and sense of coherence at age 15
Social risk factors: parental relations and family function at age 15
Coping strategies: avoidance strategies and support seeking at age 15
Indicators of social status: social position in peer group and social position in society at age 15
To examine the continuity of being bullied from age 15 to age 18