Adolescent non-suicidal self-injury (NSSI) is a serious psychological and behavioral problem. Long-term NSSI behavior can damage individual health and well-being (White et al., 2021) and may ultimately lead to adolescent suicide (Muehlenkamp, 2005; Hawton et al., 2012; Tanner et al., 2015; Xu et al., 2019). The reported prevalence of NSSI among Chinese adolescents ranges from 14–34%. (Han et al., 2018; Li et al., 2020; Lan et al., 2022; Hu et al., 2023), indicating the severity of the issue. Adolescent bullying has also been discussed extensively. Bullying has a negative impact on adolescent physiology and psychology and is related to NSSI behavior (Huang et al., 2022). However, some scholars posit that the social support individuals receive has a greater impact on their NSSI behavior (Yang et al., 2015). The family plays a crucial role as an environmental factor in the growth and development of adolescents, and parental support has an vital impact on adolescent NSSI behavior (Kidd et al., 2006). Peer support, as another important social support subsystem, can affect adolescent NSSI behavior (Peng et al., 2019). Positive peer and family relationships have been shown to moderate interpersonal problems and help mitigate or reduce NSSI behavior (Adrian et al., 2011; Christoffersen et al., 2015). Drawing from previous research experiences, it's evident that parental support and peer support are closely linked to adolescent NSSI behaviors, while adolescent encounters with bullying are also connected to NSSI incidents. Yet, the precise mechanisms by which parental support and peer support influence adolescent NSSI behaviors among bullying victims remain unclear, warranting a more comprehensive exploration. Consequently, this study will delve into the combined effects of parental support and peer support on adolescent bullying and NSSI, alongside an examination of how social connectedness mediates the relationship between adolescent bullying and NSSI. The ultimate goal is to establish a theoretical foundation for strategies aimed at preventing and intervening in adolescent NSSI behaviors.
1.1 Relationship between Bullying and NSSI
Bullying is “deliberate, repetitive, negative (unpleasant or hurtful) behavior by one or more individuals against a person who has difficulty defending himself or herself” (Olweus and Limber, 2010). According to general strain theory (GST), bullying can have lasting negative physical and psychological effects for adolescents(Huang et al., 2022). Previous studies have shown that adolescent bullying is associated with NSSI risk (Jantzer et al., 2015; Huang et al., 2022) and an important predictor of adolescent NSSI (Hamada et al., 2018). Moreover, adolescents who have experienced bullying have a much higher risk of NSSI than peers who have not (Huang et al., 2022). Bullied adolescents may use NSSI as a way to seek attention and help (Heerde and Hemphill, 2019), relieve stress related to bullying (Serafini et al., 2023), and reduce their inner guilt and pain by punishing themselves (Hawton et al., 2012; Zetterqvist, 2015; Meszaros et al., 2017). For instance, when individuals face interpersonal pressures like physical or verbal abuse, they may find it challenging to effectively handle the ensuing distress(Serafini et al., 2021). Consequently, they may perceive NSSI as a coping strategy to regulate and alleviate acute negative effects or emotional arousal (Serafini et al., 2021), aiming to alleviate their suffering (Zetterqvist, 2015). Therefore, for adolescents who may be exposed to bullying, taking steps to avoid the negative consequences of bullying can help reduce their engagement in NSSI behavior(Adrian et al, 2011; Jantzer et al., 2015; Huang et al., 2022). In order to verify the impact of bullying on NSSI, this study puts forward hypothesis H1: There is a significant positive correlation between adolescent bullying and NSSI.
1.2 Relationship between Parental and Peer Support and NSSI
According to Bronfenbrenner's ecological system theory (1979), the development of an individual is shaped by the reciprocal interaction between the individual and their surrounding environment. Within this framework, peers and parents hold substantial importance as influential factors in the environment, which greatly impacts the growth and development of adolescents (Shek and Sun, 2014).
The functional theory of NSSI (Nock, 2010) holds that individuals with a subordinate status or social failure can adopt NSSI behavior to increase the attention and support they receive. For example, the lack of support from family and the pressure from peers can influence an individual's engagement in NSSI behavior(Brausch and Gutierrez, 2010; Baetens et al., 2015; Burke et al., 2015; Tanner et al., 2015). Positive family functioning has been shown to effectively prevent adolescent NSSI behavior (Kidd et al., 2006; Jiang et al., 2016; White et al., 2021), or is beneficial in stopping it (Tatnell et al., 2014), whereas poor family relationships can exert pressure on adolescents that leads lead to NSSI behavior (Wang et al., 2011). Peers also play an important role in adolescent growth and development, and improving peer relationships and providing peer support may mediate interpersonal problems and help alleviate NSSI behavior (Adrian et al., 2011).
Further, positive family relationships can moderate interpersonal problems (e.g., peer relationships) and help mitigate or reduce NSSI behavior (Adrian et al., 2011; Christoffersen et al., 2015). Negative events in peer relationships can contribute to the occurrence of adolescent NSSI behaviors (Peng et al., 2019), and close parent–child relationships can reduce individual NSSI behavior and be a protective factor for adolescents who engage in NSSI because of poor peer relationships (Kidd et al., 2006). Therefore, parental and peer support play a significant role in the prevention of adolescent NSSI. However, how parental and peer support jointly influence adolescent NSSI behavior still requires further exploration. This study proposes hypothesis H2: High levels of parental and peer support have a significant positive effect on adolescent NSSI.
1.3 Relationships among Parental Support, Peer Support, Bullying, and NSSI
The environmental theory model of NSSI posits that the environment in which an individual lives is a stable system. When the equilibrium of the system is threatened, individuals may engage in NSSI as a means to restore physical balance caused by environmental factors (Feng, 2008). A study demonstrated that while parental support can serve as a protective factor against bullying and other forms of harm, it may also heighten the risk of engaging in NSSI behavior (Baetens et al., 2015). This is because adolescents may adopt and even repeat NSSI behavior to receive parental attention (Tschan et al., 2019).
Life model theory argues that problems in life reflect an imbalance between people and the environment, and a poor interpersonal process will affect the outcome of an individual’s personal life and their response to environmental factors (Payne, 2014). Some studies suggest that adolescent NSSI behavior usually occurs in a social environment with negative interpersonal influences and emotional distress (Hankin and Abela, 2011; Jantzer et al., 2015). For adolescents, bullying and being bullied are negative interpersonal events (Scholte et al., 2013), and may lead to NSSI without intervention or adjustment, thereby affecting their interpersonal communication and emotions (Burke et al., 2015; Huang et al., 2022). Individuals who experience bullying are gradually socially excluded, resulting in lower social competence and self-esteem (Chiu and Vargo, 2022), and a lack of peer support can increase loneliness, social frustration, and low self-worth (Nation et al., 2008).
As bullying victimization among adolescents predicts NSSI behavior (Hamada et al., 2018), and parental and peer support mitigate the relationship between adolescent bullying and NSSI. Therefore, exploring how the matching of parental and peer support affects the internal relationship between bullying and NSSI in adolescents has positive practical significance for preventing and intervening those who suffer from bullying and exhibit NSSI behavior. Thus, this study proposes hypothesis H3: Bullying mediates the relationship between the matching effects of parental and peer support and NSSI.
1.4 Role of Social Connectedness in Bullying and NSSI
Social connectedness is the subjective perception of intimacy in one’s surrounding interpersonal relationships and regular cognition of interpersonal patterns, reflecting one’s internal sense of belonging (Lee and Robbins, 1998; Xie, 2021). Studies have shown that social connectedness is a protective factor against common psychological distress symptoms that are negatively correlated with interpersonal problems and positively correlated with social support (Lee et al., 2001). A lack of social support and connectedness affects peer acceptance of victims of bullying (Longobardi et al., 2021) and increases NSSI behavior in those victims (Esposito et al., 2019). Studies have shown that social connection regulates the relationship between risk factors and risk (Taliaferro et al., 2019). Bullying victims’ perceived social support can alleviate their internal distress (Chiu and Vargo, 2022). In contrast, a lack of perceived social support (Rueger et al., 2016) is closely related to NSSI behavior (Nock et al., 2006). For instance, in cases where parents struggle to find effective approaches for engaging with their children (White et al., 2021), children with NSSI behavior may choose to seek help from outside rather than their parents (Fortune et al., 2008; Berger et al., 2013). Hence, promoting enhanced social connectedness may have a beneficial impact on preventing NSSI among adolescents (Estrada et al., 2019).
For adolescents personally, parental and peer support are objectively present, while the social connection ability of adolescents reflects how effectively they perceive and utilize the level of parental and peer support. Therefore, this study also attempts to explore the moderating role of social connectedness ability between parental and peer support in the relationship between bullying and NSSI. This study proposes hypothesis H4: Social connectedness moderates the relationship between "parent-peer support match," bullying, and NSSI.
In summary, current studies have shown that adolescents' parental support and peer support are closely related to adolescent bullying and NSSI, and social connectedness can help alleviate the effects of adolescent bullying and NSSI. However, it is still unclear which factor, parental support or peer support, plays a primary role when adolescents experience bullying at school, or how the combined effect of these two factors influences the mechanism of adolescent bullying and NSSI behavior. For individual adolescents, family and school are important environmental factors in their growth and development. Thus, by discussing the role of NSSI, bullying, and parental and peer support, as well as the mediating role of social bonding in bullying and NSSI, the foundation is laid for the effective "home-school collaborative" model for the prevention and intervention of NSSI in adolescents. This study will build upon previous research to explore the mechanisms by which parental support and peer support impact adolescent bullying and NSSI behaviors, while proposing a moderated mediation model (as shown in Fig. 1). The main focus will be on investigating three specific issues: (1) using polynomial regression and response surface analysis, this study examined the influence of parental and peer support on adolescent bullying; (2) mediating role of adolescent bullying between parental support, peer support, and NSSI behavior; and (3) moderating role of social connectedness between adolescent bullying and NSSI behavior.
(Fig. 1 near here)