Introduction
Adverse childhood experiences (ACEs) are defined as potentially traumatic or otherwise negative events in a child’s social or familial environment (e.g., child abuse, neglect) that may cause distress or harm and disrupt the child’s development and well-being (Felitti et al.,
1998). Prevalence estimates suggest that approximately 60.1% of people experience at least one ACE during their childhood and 16.1% experience four or more ACEs (Madigan et al.,
2023). ACEs have been consistently linked with poor mental health outcomes in adolescents, reflecting a dose-dependent relationship whereby more ACEs are linked with poorer mental health (Green et al.,
2010). The original ACEs were based on seminal work by Felitti et al. (
1998) and focused on areas of abuse and neglect, as well as household dysfunction (e.g., parental alcohol abuse). Building on these original ACEs, scholars have been working to redefine and update the original ACEs to reflect other relevant adversities that impact the mental health of young people (Finkelhor et al.,
2013). Such work has suggested that bullying victimization may be considered an ACE (Karatekin & Hill,
2019). Bullying refers to repeated, intentional acts of interpersonal aggression with an imbalance of power (Olweus,
1991). This could include verbal threats, physical harm, and social exclusion both in-person and online (cyberbullying; (Smith et al.,
2008)). Like the original ACEs, bullying victimization is linked to mental health problems, and potentially long-lasting effects (Brunstein Klomek et al.,
2019). This study builds on emerging evidence suggesting that ACEs and bullying victimization co-occur, by investigating how this co-occurrence impacts mental health problems, especially during early adolescence.
The developmental trajectory from childhood to early adulthood is a crucial period, as it is vulnerable to the establishment of several health-related risk factors and development of mental health problems (Solmi et al.,
2021). From a developmental perspective, ACEs are commonly experienced during early childhood or persistently throughout childhood (Fisher et al.,
2010). In contrast, issues with bullying victimization are more common during late childhood and early adolescence, as social contexts change throughout development and children begin to spend more time with their peers (Hawes et al.,
2021). Thus, understanding the interplay between ACEs and bullying victimization on mental health problems in early adolescents is critical for informing early interventions. Previous research on contextual factors relating to bullying found that several family characteristics such as harsh parenting (Barker et al.,
2008), low family income (Barker et al.,
2008), and child maltreatment place children at greater risk for bullying victimization (Bowes et al.,
2009). As such, it is important to further investigate the association between ACEs and bullying victimization to understand whether both are independently associated with mental health problems, or whether having a history of ACEs amplifies the negative association between bullying victimization and mental health problems.
The cumulative risk model is the most prominent theoretical framework to understand the impact of ACEs. The cumulative risk model proposes that cumulative adversity is linearly associated with negative outcomes, whereby more adversity is linked with more negative outcomes (Evans et al.,
2013). Research tends to support this model (Appleyard et al.,
2005), whereby the accumulation of toxic stress generated by ACEs over time is thought to explain the dose-dependent association between ACE exposure and mental health outcomes (Shonkoff et al.,
2012). However, the model has also been criticized as it implies that all negative events are equal and that all potential combinations have the same outcome (Jaen et al.,
2023). Previous research has shown that some ACEs (e.g., childhood sexual abuse) are linked with worse outcomes than others (e.g., parental separation), and that there are interactive effects between different combinations of ACEs (Putnam et al.,
2020).
While interactive effects have been observed among the traditional ACEs, whereby some combinations have a multiplicative effect on mental health problems (i.e., experiencing more adversities does not just increase the risk for mental health problems linearly, but proliferates the risk), this has not been extended to bullying victimization. It is unclear whether bullying victimization would have a cumulative effect, as predicted by the cumulative risk theory, or a multiplicative effect on mental health problems in adolescents. Here, a cumulative effect refers to both the exposure to ACEs and exposure to bullying victimization being associated with more mental health problems in a dose-dependent relationship whereby greater exposure is linked with worse outcomes. A multiplicative effect would see an interaction of the ACEs and bullying victimization whereby one might alter the direction of the relationship with mental health problems such that it amplifies the problem. For example, having been exposed to ACEs may amplify the relationship between bullying victimization and mental health problems. One study to date has investigated the overlap between bullying victimization and substance use in adolescents (Afifi et al.,
2020). Findings support the cumulative risk model, whereby both ACEs and bullying victimization were uniquely associated with substance use without interacting with one another. However, no such research has yet explored mental health problems at a broader scale, including internalizing problems (i.e., depression, anxiety), in the context of early adolescence.
Understanding whether ACEs and bullying victimization follow a cumulative or multiplicative pattern will have important implications for both the conceptualization of ACEs and early intervention. According to the cumulative risk model, current conceptualizations of ACEs partly rely on the understanding that ACEs are interrelated and cumulative in explaining outcomes. If the overlap between ACEs and bullying victimization is cumulative in terms of mental health problems, this will provide further evidence for including bullying victimization in screening tools for ACEs. However, if the overlap is multiplicative ACEs and bullying victimization may be better understood, and screened for, as separate risk factors for mental health problems.
Discussion
Currently, little is known about how the co-occurrence of ACEs and bullying victimization is associated with mental health problems in early adolescents. In line with previous research, findings showed strong and independent associations between both ACEs and bullying victimization, with mental health problems (Afifi et al.,
2020). Overall, the findings provide further evidence for a cumulative risk model of adversity (McLaughlin et al.,
2012).
Similar to previous research on ACEs, both internalizing and externalizing problems showed similar patterns of associations (Brieant et al.,
2022). Both exposure to ACEs and bullying victimization may place adolescents at risk for any mental health problem, rather than specific symptoms. Indeed, similar underlying mechanisms may link ACEs and bullying victimization to mental health problems, such as emotion dysregulation (Herd & Kim-Spoon,
2021), low self-esteem (Kim et al.,
2022),and maladaptive coping (Trompeter et al.,
2018). However, to date, such research has largely focused on specific types of ACEs or bullying victimization. Based on findings from the current study, future research should consider both cumulative ACEs and bullying victimization to further understand the underlying psychological mechanisms linking these exposures to mental health problems. While the current study was framed within the cumulative risk model of adversity, other models and approaches should be tested to determine how to best conceptualize co-occurring adversities throughout childhood. For example, future research should examine how bullying victimization fits within the threat-deprivation model of adversity, which posits that adversities have differential impacts on development depending on whether they align with a threat-response (e.g., family conflict) or a deprivations-response (e.g., emotional neglect) (McLaughlin & Sheridan,
2016).
While the findings support a cumulative risk pattern overall, one exception regarding cumulative bullying victimization and externalizing problems should be noted. That is, among adolescents with ACE exposure there was a greater difference in externalizing problems between adolescents with high cumulative bullying exposure and low cumulative bullying exposure compared to those with no ACE exposure (see Figure
4). Adolescents who have a history of ACE exposure may be at increased risk for externalizing problems if they also experience bullying victimization. While the finding was small in effect size, this finding has important implications for early intervention efforts targeting externalizing problems that typically onset in adolescence, such as substance use (Behrendt et al.,
2009). Such intervention efforts may benefit from targeting early adolescents who have experienced both ACEs and bullying victimization to reduce externalizing problems to avoid escalation throughout adolescence.
The present study findings have significant policy, clinical, and public health implications, particularly for screening and prevention efforts. ACEs affect early adolescents at a critical time of development, and there have been ongoing calls for screening during primary care visits (Pardee et al.,
2017). Findings from the current study suggest that in addition to screening for the original ACEs in pediatric care settings for example, screening for bullying victimization may improve detection of adversity and more accurately identify adolescents at risk for mental health problems. Schools and educators should be aware of the overlap between ACEs and bullying victimization and consider that adolescents who have experienced ACEs and/or bullying victimization are likely to be experiencing other types of victimization and/or mental health problems. In particular, while educators may not have insight into specific childhood adversities faced by students, they might have knowledge about general adversity. However, more research is needed to understand potential protective factors that might mitigate the association between ACEs, bullying victimization and adolescent mental health problems.
Despite these important implications, several limitations should be noted. Firstly, due to the observational nature of the study, no causal relationships can be made, and residual confounders may exist; however, known confounders were adjusted for. Secondly, questions regarding ACEs and bullying victimization were retrospective and hence vulnerable to recall bias and social desirability bias. Lastly, our conceptualization of bullying victimization was broad by including any instances of bullying victimization. This was in part due to the nature of the cyberbullying measure, which did not capture the frequency of bullying. Future research should examine whether different patterns hold when examining chronic bullying victimization.
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