Online victimization by peers as well as its adverse consequences have become a serious public health problem. According to a review published in 2015, most studies found that the proportion of students who reported to be victims of cyberbullying ranged from 20% to 40% [1]. Data from the United States in 2015 reported that 15.5% of high school students have been bullied online [2]. Similarly, about 15% of teenagers reported being victims of cyberbullying in countries such as France, England, and Spain [3-5]. Among the Chinese population, the prevalence of cyber victimization has been reported as 18.4% and 11.9% among adolescents from Taiwan and Hong Kong, respectively [6, 7]. However, a recent study, conducted in ShenZhen Guangdong, China, showed a lower prevalence (8.7%) of cyber victimization among middle-school students [8]. In addition, a relatively higher rate of cyber victimization has also been reported (37.3% and 32%) among teenage students in Romania and Bangladesh, respectively [9, 10].
To date, a number of studies have been conducted that examined the impact of peer victimization on their physical and mental health. It has been shown that peer victims report higher rates of suicidal ideation at the age of 13 and conducted suicide attempts at the age of 15 compared with those who have not been victimized [11]. Additionally, the long-term impacts of bullying by peers on mental health have been found to persist into young adulthood [12]. With respect to online peer victimization, increased internalizing disorders [3],externalizing disorders, substance-use problems [13, 14], and a high risk of depression have been identified in victims of cyberbullying compared with nonvictims [4, 6]. The victims of cyberbullying showed significantly higher rates of suffering from psychiatric disorders compared with non-victims[10] . A study conducted in Australia has consistently suggested poor mental health among youths who experienced cyber victimization [15, 16]. Furthermore, experience of cyber victimization was found to be related to posttraumatic stress disorder (PTSD) symptoms via studying teenagers sent to the emergency department [16]. A meta-analysis demonstrated the link between suicides and both types of peer victimization (cyberbullying and face-to-face bullying), within which, cyberbullying exerted a stronger effect on suicidal ideation compared with face-to-face bullying [17]. With regard to gender differences, more emotional symptoms were observed in females, whereas more risk behavior was observed in males when subjected to cyber victimization [18]. In addition to psychological symptoms, somatic problems (such as headaches and abdominal pain) have been associated with cyberbullying [19]. Furthermore, cyberbullying victimization has been associate with a significant decrease in subjective wellbeing [20].
Given that a strong and reliable association exists between cyber victimization and critical physical and mental health problems, finding ways to intervene or prevent such problems is necessary. However, only few studies have explored the potential mechanisms underlying the links between cyber victimization and the negative outcomes mentioned above. One study conducted among Italian adolescents found that psychological resilience plays a mediating role between cyber victimization and emotional symptoms [21]. Family dinners were proposed to moderate the relationship between cyber victimization and mental health problems [13]. In addition, connectedness between students and school was identified to function as a moderator by alleviating the association between cyber victimization and suicide [22]. This study hypothesized that victims may search for other means, such as a virtual reality to cope with the pressures of being bullied. A Chinese study verified that peer victimization during 7th grade is a strong predictor for Internet-gaming addiction during the 9th grade [23]. Consistently, a significant association between peer victimization and pathological Internet use ( assessed by the Young Diagnostic Questionnaire ) has been reported in a study on German adolescents [24]. Moreover, Internet addiction was shown to be associated with cyber victimization [25, 26]. In addition, the bidirectional relationship between cyber victimization and Internet use was shown in a Chinese study, suggesting a higher likelihood of cyber victimization among youths with Internet risk behavior (e.g., chat with strangers, and post personal pictures) [6]. Internet use (more than two hours per day) was shown to predict a higher probability of being cyberbullied [9].
Internet addiction has also been considered as a psychological escape mechanism to avoid real-world problems [27] and has been proven to be associated with both mental and physical symptoms. Examples are the higher risk of Internet addition, inferior the mental health outcomes, suicidal ideation, depression, and anxiety [28, 29]. In addition, intense back pain, headaches, and increased body mass index have been observed among Internet-addicted youths [30]. Furthermore, nternet addiction has been identified to negatively impact the ophthalmologic system in the form of eye strain, and an increase of sleep disorders has been reported among Internet-addicted youths compared with non-addicted individuals [31]. Cyberbullying could occur via a special path that could lead to increased severe harm among individuals who have been bullied in their real life [32].
Based on previous research, this study hypothesized that cyber victimization is associated with Internet addiction, which in turn is related to both physical and mental health. Thus, the present study examined whether Internet addiction mediates the association between cyber victimization and both psychological and physical health.
In addition, problematic Internet use (PIU, measured through Internet addiction test), has been linked to decreased physical activity [33-35]. Physically active youths tend to obtain increased satisfaction from sleep and are less likely to develop Internet addiction compared with their peers who are physically inactive [36]. In fact, exercise rehabilitation has been applied as a measure to alleviate smartphone addiction [37].
Further studies supported that physical exercise can improve psychological and physical symptoms. Long-term physical exercise has been shown to improve negative symptoms in inpatients with mental health issues [38]. Moreover, regular exercise reduces anxiety and depression and improves self-esteem [39, 40]. From the perspective of neurobiology, physical activity leads to the release of endorphins, dopamine, noradrenaline, and serotonin, all of which can ease pain and promote a sense of euphoria and wellbeing [41]. Despite its positive effects, the role of physical exercise in the relationship between Internet addiction and both mental and physical health remains unknown. Hence, the second purpose of this study was to examine whether physical exercise plays a moderating role in the mediation posed above.