Affective lability refers to shifts in the frequency, speed, and range of affective states (Oliver and Simons, 2004) and constitutes an important feature of psychopathology. According to previous studies, affective lability is associated with various mental and behavioral problems, including borderline personality disorder (Association, 2013; Zimmerman et al., 2017), bipolar disorder (BD) (Aminoff et al., 2012; Henry et al., 2008), major depressive disorder (Eldesouky et al., 2018; Thompson et al., 2011), attention-deficit hyperactivity disorder (Helfer et al., 2019; Skirrow and Asherson, 2013), and problem drinking (Atkinson et al., 2021; Peterson et al., 2021). In addition to its role in psychopathology, affective lability is an important concern in the normative psychological development of adolescents. The development of affect was found to change dynamically from early to late adolescence (Reitsema et al., 2022) and was influenced by the neurological, physiological, cognitive, and social changes that occur during this period (Coe-Odess et al., 2019). As a result, the affect of adolescents is highly turbulent. Thus, research is needed to explore factors related to affective lability among adolescents. Childhood trauma, which refers to maltreatment occurring in the family environment during childhood and can be further categorized as emotional, physical, and sexual abuse, or emotional and physical neglect (Bernstein et al., 2003), is an important factor related to affective lability and has attracted researchers' attention. For example, affective lability was reported to relate to childhood trauma among patients with BD (Etain et al., 2017; Marwaha et al., 2016). Other studies have reported that childhood trauma was related to affective lability in the general adult population (King, 2022; Weiss et al., 2018). However, as shown by our previous literature review, there is a lack of relevant research on the direct relationship between childhood trauma and affective lability among adolescents. Given the potential relationship between childhood trauma and psychological and behavioral problems (Herzog and Schmahl, 2018; Hunt et al., 2017), we predicted that childhood trauma is related to affective lability among adolescents.

Concerns about body image, defined as how people experience their own physical appearance, including perceptions and attitudes related to their appearance (Cash, 2012), is another major issue during adolescence. According to a 10-year national longitudinal study on ideal body image, adolescents have been increasingly pursuing thin-body silhouettes, while the incidence of overweight/obesity is increasing over time (Min et al., 2018). This means that some adolescents may be dissatisfied with their body image. McLean et al. reported that 37.9 % and 20.7 % of adolescent boys and girls, respectively, experienced moderate, and 6.8 % and 19.6 % experienced clinically significant body image dissatisfaction (McLean et al., 2022). Body image dissatisfaction was found to be associated with an increased risk of depression and anxiety among adolescents (McLean et al., 2022; Soares Filho et al., 2020; Solomon-Krakus et al., 2017; Vannucci and Ohannessian, 2018). Previous research also reported a link between body image dissatisfaction and emotion dysregulation (Kelly et al., 2020; Lev-Ari et al., 2021). A study of young men by Wyssen et al. found that body image dissatisfaction was a predictor of emotion dysregulation (Wyssen et al., 2016). As affective lability is one important aspect of emotion dysregulation, we hypothesized that body image dissatisfaction might be related to affective lability.

Evidence has suggested that childhood trauma may increase the risk of body dissatisfaction in adolescents. Childhood trauma was found to be a significant predictor of body image dissatisfaction (Constantian and Zaborek, 2021; Vartanian et al., 2018). For example, Constantian et al. found that adverse childhood experiences positively predicted body shame in a plastic surgery population (Constantian and Zaborek, 2021). In addition, in a study of adolescents, Emirtekin et al. reported a correlation between childhood emotional maltreatment and body image dissatisfaction (Emirtekin et al., 2019). Considering the interrelationships among body image dissatisfaction, childhood trauma, and emotion dysregulation, we hypothesized that body image dissatisfaction might mediate the relationship between childhood trauma and affective lability among adolescents.

Being bullied is a serious negative life event that occurs between peers and refers to exposure to aggressive and intentional actions from a group or individual over time. It involves an imbalance of power between the victim and the perpetrator (Olweus, 1993). Being bullied has attracted concern from researchers due to its widespread occurrence worldwide and harm to the psychological and physical health of adolescents (Arslan et al., 2012; Eyuboglu et al., 2021; Jadambaa et al., 2019; Loch et al., 2020). Previous studies reported that exposure to childhood trauma made adolescents more vulnerable to bullying victimization (Forster et al., 2020; Zuo et al., 2021). Just as childhood trauma is associated with affective lability, being bullied is negatively associated with emotion-regulating abilities (Herd and Kim-Spoon, 2021; Kliewer, 2016; Trompeter et al., 2018). Furthermore, there is evidence that adverse experiences occurring at different times (childhood and young adulthood) have a cumulative effect on the deterioration of emotion regulation (Stern and Thayer, 2019). Additionally, experiencing recent stressful life events was more likely to trigger depression among adolescents exposed to childhood trauma through reduced hippocampal and amygdala volume (Weissman et al., 2020). Thus, childhood trauma may interact with recent stressful life events, triggering more negative emotional reactions. Since, unlike childhood trauma, being bullied can be a recent negative experience for adolescents, we speculate that childhood trauma and recent experiences of being bullied may have an interactive impact on affective stability.

Additionally, being bullied was also found to relate to body image dissatisfaction among adolescents (Day et al., 2022; Duarte et al., 2015; Lee and Vaillancourt, 2019; Ramos Salazar, 2021) and may influence adolescents' body images. For example, many cross-sectional studies found that being recently bullied was associated with self-perceptions of being overweight (Lian et al., 2018; Lin et al., 2018; Wilson et al., 2013). Brixval et al. found that self-perceived body image, in turn, had an indirect impact on overweight adolescents, making them more vulnerable to bullying (Brixval et al., 2012). Accordingly, we hypothesized that being bullied may moderate the above mediating model on the relationship between childhood trauma and affective lability among adolescents.

Gender differences may also influence the relationship between childhood trauma and affective stability among adolescents. For example, Wei et al. reported gender differences in the positive association between childhood trauma and depressive symptoms, which was stronger for females than for males (Wei et al., 2021). Regarding differences in affective stability, there is evidence that affective development from middle childhood to late adolescence varies with gender, with girls experiencing earlier decreases in positive affect and earlier increases in negative affect compared to boys (Abitante et al., 2022; Griffith et al., 2021). Moreover, there are also gender differences in emotion-regulating ability, as different brain networks were employed when men and women regulated negative emotions (Stoica et al., 2021). In summary, we have reason to assume that gender may moderate the relationship between childhood trauma and affective lability among adolescents. Similarly, body image dissatisfaction (Bully and Elosua, 2011; Fernández-Bustos et al., 2019; Hockey et al., 2021) and environmental factors related to self-perceived body image (Michael et al., 2014) also differ with gender. Luevorasirikul et al. found that women were more concerned about their body shape and tended to be dissatisfied with it, and the development of their body image concern was more susceptible to social and cultural factors (Luevorasirikul et al., 2012). Given these findings, we explored the relationship between childhood trauma, body image dissatisfaction, and affective lability by gender and hypothesized that gender might moderate the above mediating model of the relationship between childhood trauma and affective lability among adolescents (the hypothesis model in this study is shown in Fig. 1).