Abstract

Introduction

The past decade has witnessed a rapid rise in smartphone use. As of December 2018, the number of Chinese youth netizens exceeded 200 million, of which 90% were smartphone users (China Internet Network Information Center, 2019). Particularly among adolescents, the smartphone, as an internet terminal, is the main point of access to the internet (We Are Social and Hootsuite, 2018; China Internet Network Information Center, 2019). However, despite their portability, convenience, and versatility, smartphones are causing some problems, one of which is referred to as “problematic smartphone use” (PSU) (Kuss et al., 2018; Xie et al., 2018). PSU is defined as inappropriate or excessive uses of smartphones that might interfere with everyday life, impair social functions, and/or lead to psychological and/or behavioral problems (Billieux et al., 2015). The concept of PSU mainly derives from two similar concepts. “Problematic mobile phone use” is a term and concept found in recent literature (De-Sola et al., 2017; Jiang and Zhao, 2017) and reports published before the smartphone boom (Bianchi and Phillips, 2005; Jenaro et al., 2007; Chóliz, 2010), and “problematic internet use” or “internet addiction” is a concept that has provided theoretical and methodological support for studies on PSU (Salehan and Negahban, 2013; Lee et al., 2014; Lin et al., 2014).

Many studies have found adverse consequences of PSU, particularly for adolescents. It has a negative influence on their physical health, such as headaches (Söderqvist et al., 2008), sleep problems (Söderqvist et al., 2008; Lemola et al., 2015; Xie et al., 2018), eye and vision problems (Xie et al., 2018), and so on. Other studies found that PSU damaged adolescents’ psychological and social functions (Yen et al., 2009), and it led to behavioral problems, such as aggression and smoking (Augner and Hacker, 2012). Furthermore, PSU might be associated with concentration difficulties (Söderqvist et al., 2008) and poor academic performance (Hawi and Samaha, 2016; Samaha and Hawi, 2016; Yang et al., 2019).

Because PSU might impede adolescents’ healthy development, concerns are growing about the possible correlates of PSU, such as various features of personality, emotion, interpersonal relationships, and so on (Bianchi and Phillips, 2005; Butt and Phillips, 2008; De-Sola et al., 2017; Wang et al., 2017; Kim and Koh, 2018). Some scholars proposed that PSU is an addiction-like phenomenon, similar to problem gambling (Billieux et al., 2015; Wang et al., 2016; Elhai and Contractor, 2018). Therefore, many studies have adopted the behavioral addiction perspective (Jiang and Zhao, 2017; Ihm, 2018). Because adolescents are in a critical period of physical and psychological development, exploring the causes of PSU helps us better mitigate smartphones’ adverse consequences.

Self-esteem deserves attention as a possible cause. Self-esteem is about mental representations of the self-regarding overall feelings of self-worth and self-acceptance (Rosenberg, 1965), and self-esteem is essential to adolescents’ social development and social adaptation (Robins and Trzesniewski, 2005; Trzesniewski et al., 2006). Based on the ecological systems theory and dual-factor resiliency theory, an explanatory model of adolescent problem behavior recognizes low self-esteem as one of the individual-level risk factors (Jessor et al., 2003). Many previous studies have found robust associations between low self-esteem and behavioral problems or deviance, and it has been related to aggression (Donnellan et al., 2005; Garofalo et al., 2016), smoking (Carters and Byrne, 2013), alcohol and/or drug use (Wild et al., 2004; Kavas, 2009), problem gambling (Rodda et al., 2004), and delinquency (Donnellan et al., 2005). Meanwhile, a cognitive-behavioral model of internet addiction also suggests that low self-esteem is a critical aspect of maladaptive cognition of the self, which is the core factor leading to problematic internet use (Davis, 2001). Of particular relevance to the current study, research has linked self-esteem and PSU such that low self-esteem is a risk factor of PSU (Butt and Phillips, 2008; Ha et al., 2008; Billieux, 2012; Isiklar et al., 2013), and self-esteem often has been identified as an antecedent of PSU. Wang et al. (2017) suggested that low-quality peer relationships among adolescents might lead to low self-esteem, which, in turn, might lead to PSU. Kim and Koh (2018) also found that low self-esteem was associated with PSU.

Although many studies have found direct relationships between self-esteem and PSU, more research about the internal mechanisms is needed. First, a systematic review pointed out that the link between self-esteem and PSU found by previous studies is inconsistent, such that the bivariate effects were small or moderately strong and the effects found in multivariate analyses were weaker or non-significant (Elhai et al., 2017). Therefore, exploring mediating and moderating factors might shed light on the relationship. In addition, a better understanding of mediating and moderating influences might improve our understanding of the etiology of PSU and support development of effective interventions.

Davis’s (2001) cognitive-behavioral model proposes that psychological distress, such as depression, is an essential and significant catalyst of problematic internet use. Recent studies on PSU indicated that depression predicted PSU (Panova and Lleras, 2016; Kuss et al., 2018), and it has been linked to problematic internet use, problem gambling, and other behavioral problems (Armstrong et al., 2000; Rodda et al., 2004). Kim et al. (2015) suggested that, when individuals felt depressed, they tend to use their smartphones to cope with their negative emotions. In other words, using a smartphone is considered an experiential avoidance strategy to divert aversive emotional content. However, experiential avoidance is ineffective for achieving that outcome, and, instead, it has adverse consequences (Kim et al., 2015; Chou et al., 2018). Meanwhile, influential theories of depression have considered aspects of low self-esteem as a vulnerability factor that confers risk to depression. For instance, Orth and Robins (2013) validated the vulnerability model of the relationship between low self-esteem and depression, which considered self-esteem to be a leading cause of depression. Further, individuals with lower self-esteem was more likely to develop depression than those with high self-esteem (Orth et al., 2014). From the view of the buffer hypothesis, low self-esteem is also one of the most important susceptibility factors to depression, which tends to lead to depression in individuals under the influence of stressful life events (Murrell et al., 1991; Hankin et al., 2007). In particular, the hopelessness and self-esteem theory of depression holds that depression occurs as a result of negative attributional style, low self-esteem and negative life events, where hopelessness plays a mediating role, low self-esteem playing a stimulating role, and high self-esteem acting as a buffer (Metalsky et al., 1993). A meta-analysis of longitudinal studies supported this contention, revealing that the effect of self-esteem on depression was significantly stronger than that of depression on self-esteem (Sowislo and Orth, 2013). This implies that depression might play a mediating role in the relationship between self-esteem and PSU.

Interpersonal trust is vital to healthy psychosocial development and key to the formation and maintenance of healthy interpersonal relationships (Gurtman, 1992; Simpson, 2007). Interpersonal trust has been defined as a psychological state of voluntarily placing oneself in an undefended or vulnerable position based on confident expectations of the good intentions and actions of others (Rousseau et al., 1998; Haselhuhn et al., 2015). The emancipation theory of trust proposes that people with high levels of interpersonal trust often expand their social networks (Yamagishi and Yamagishi, 1994; Yamagishi, 1998). Previous studies also found that interpersonal trust among children and adolescents related to higher social status (Buzzelli, 1988), less loneliness (Rotenberg et al., 2004), and better-quality peer relationships (Rotenberg et al., 2004). Ihm (2018) interpreted PSU as a social problem stemming from a lack of offline social networks and in-person social support. When an individual’s needs are not being met, she or he might turn to virtual sources of support as an alternative, which might lead to pathological smartphone usage. Davis’s (2001) cognitive-behavioral model also proposes that the need for social contact and reinforcement obtained online would increase the desire to remain in a virtual social life. From this perspective, the benefits of interpersonal trust mentioned above might reduce the emergence of PSU by providing alternative ways to meet individuals’ needs.

Previous studies have also found a negative association between trust and depression (Kim et al., 2012; Betts et al., 2017). Specifically, lower interpersonal trust increased the incidence of depression (Kim et al., 2012; Frank et al., 2014; Betts et al., 2017), whereas higher interpersonal trust (as a component of social capital) buffered the effects of financial stress on depression (Frank et al., 2014). Moreover, individuals with higher interpersonal trust had better psychosocial adjustment (Lester and Gatto, 1990; Rotenberg et al., 2004). A study of Chinese and American adolescents and young adults found that interpersonal trust facilitated the support-seeking process and was associated with appropriate help-seeking, which, in turn, predicted the likelihood of expressing emotional distress to friends (Mortenson, 2009). In this way, trust might also mitigate the adverse effects of depression. Therefore, interpersonal trust might buffer the relationship between self-esteem and PSU via depression.

This study’s main objectives were to explore the relationships among self-esteem, depression, interpersonal trust, and PSU and to test a moderated mediation model of the influence of self-esteem on PSU mediated by depression and moderated by interpersonal trust. Based on the results of previous studies, three hypotheses were proposed as follows.

• Hypothesis 1. Self-esteem would be negatively related to problematic smartphone use.

• Hypothesis 2. Depression would mediate the effect of self-esteem on problematic smartphone use.

• Hypothesis 3. Interpersonal trust would moderate the direct and indirect relationships between self-esteem and PSU via depression. Specifically, interpersonal trust would buffer the direct effect of self-esteem on problematic smartphone use (Hypothesis 3a), and buffer the mediating influence of depression on the effect of self-esteem on problematic smartphone use (Hypothesis 3b).

Materials and Methods

Results

Moderated Mediation Effects

Hypotheses 3a and 3b were tested by estimating a moderated mediation model (model 59) with PROCESS macro (Hayes, 2013) that included age and gender as control variables.

Table 3 indicates there was a significant negative direct influence of self-esteem on depression; however, its direct effect on PSU was not statistically significant. A significant moderating effect of interpersonal trust on the direct effect of self-esteem on PSU was found (Table 3). We plotted the results for PSU predicted by self-esteem separately for low (one standard deviation below the mean) and high (one standard deviation above the mean) interpersonal trust (Supplementary Figure 1). Simple slope tests revealed that respondents with high trust and relatively high self-esteem had significantly lower PSU, β_simple = −0.16, SE = 0.07, p = 0.02, 95% CI = [−0.30, −0.02]. However, for the respondents with low trust, the direct effect of self-esteem on PSU was not statistically significant, β_simple = 0.05, SE = 0.06, p = 0.43, 95% CI = [−0.07, 0.17].

TABLE 3

Testing the moderated mediating effect of self-esteem on PSU.

Predictors	On DEP				On PSU
	β	SE	p	95% CI	β	SE	p	95% CI
Gender	0.03	0.03	0.32	[−0.03, 0.09]	0.05	0.04	0.20	[−0.03, 0.12]
Age	–0.04	0.03	0.16	[−0.10, 0.02]	0.10	0.04	0.008	[0.03, 0.18]
SE	–0.51	0.03	<0.001	[−0.58, −0.45]	–0.06	0.05	0.24	[−0.15, 0.04]
SE × IT	<0.001	0.03	1.00	[−0.05, 0.05]	–0.11	0.05	0.02	[−0.20, −0.01]
DEP					0.27	0.05	<0.001	[0.17, 0.37]
DEP × IT					–0.11	0.05	0.01	[−0.20, −0.03]
R2	0.46		<0.001		0.12		<0.001
F	108.23				11.89

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Analyses conducted using PROCESS model 59, N = 637. Gender was dummy coded (1 = female and 0 = male). SE, self-esteem; IT, interpersonal trust; DEP, depression; PSU, problematic smartphone use.

The direct effect of depression on PSU was statistically significant (Table 2). However, the relationship between depression and PSU was moderated by interpersonal trust. Simple slope tests indicated that the association of depression with PSU was weaker for respondents with high trust (i.e., one standard deviation above the mean; β_simple = 0.16, p = 0.03, 95% CI = [0.01, 0.30]) than for respondents with low trust (i.e., one standard deviation below the mean; β_simple = 0.39, SE = 0.06, p < 0.001, 95% CI = [0.26, 0.51]; Supplementary Figure 2).

Last, the bias-corrected percentile bootstrap method further revealed a significant moderated mediation effect, β = 0.12, SE = 0.05, 95% CI = [0.02, 0.22], in which interpersonal trust moderated the mediating effect of depression by buffering its influence on PSU. The indirect effect of self-esteem on PSU via depression was statistically significant for the respondents with low trust (i.e., one standard below the mean), β = −0.20, SE = 0.04, 95% CI = [−0.27, −0.13]. In contrast, this indirect effect was non-significant for respondents with high trust (i.e., one standard above the mean), β = −0.08, SE = 0.04, 95% CI = [−0.16, 0.0001]. The moderated mediation model is shown in Figure 1. Given that interpersonal trust moderated just the second stage of the mediation process, a second-stage moderation model, which is a type of moderated mediation model, was established (Hayes, 2013). Therefore, Hypothesis 3 was partially supported.

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FIGURE 1

The moderated mediation model controlling for age and gender (all coefficients standardized). SE, self-esteem; DEP, depression; PSU, problematic smartphone use; IT, interpersonal trust. *p < 0.05; ***p < 0.001.

Discussion

Empirical support exists for a link between self-esteem and PSU in which self-esteem negatively predicts PSU. However, its internal mechanisms are ambiguous. The purpose of this study was to investigate whether self-esteem indirectly related to PSU via depression and whether the direct and indirect associations between self-esteem and PSU were moderated by interpersonal trust. The findings indicated that the predictive effect of low self-esteem on PSU was mostly explained by increased depression, and it was buffered by interpersonal trust. For respondents with high trust, higher self-esteem was associated with less PSU; however, for respondents with low trust, the direct effect of self-esteem on PSU was not significant. Further, the association between depression and PSU was weaker for the high trust rather than the low trust respondents. Thus, these analyses established a moderated mediation model.

Conclusion

This study tested a moderated mediation model to examine the psychological factors underlying the relationship between self-esteem and PSU. In brief, the results found that low self-esteem was a risk factor for problematic use of smartphones in a sample of Chinese middle school students, and it predicted PSU through the level of depression, the effects of which on PSU were buffered by interpersonal trust. These findings substantially contribute to our understanding of PSU and behavioral addiction.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation, to any qualified researcher.

Ethics Statement

The studies involving human participants were reviewed and approved by the Research Ethics Committee of Renmin University of China. Written informed consent to participate in this study was provided by the participants’ legal guardian/next of kin.

Author Contributions

CL and YD analyzed the data and wrote the draft. DL and YD collected the data, supervised the study, revised the manuscript, and provided the funding sources. All authors designed the study, had full access to all the data, and have taken responsibility for the integrity of the data and accuracy of the data analysis.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgments

Footnotes

References