DISCUSSION
The findings suggested that depressive symptoms and loneliness had a significant impact on smartphone overdependence in adolescents in South Korea. Notably, the data in this study were collected from August to November 2020, during the global COVID-19 pandemic. At this time, South Korean adolescents mostly stayed home and had online classes in lieu of face-to-face classes [
16]. Therefore, this study was conducted in circumstances that restricted social interactions, and the findings are thus considerably valuable. Further, to analyze sex differences, participants were divided into groups by sex. The results showed that, regardless of sex, significant associations were found for smartphone overdependence, depressive symptoms, and loneliness.
The data provide evidence to support the need for the management of smartphone overdependence in adolescents with depressive symptoms or loneliness. Consequently, adolescents with high levels of loneliness or depressive symptoms should be screened as early as possible so that they may be guided to perform healthier and more diverse activities to prevent problematic smartphone use. Therefore, further studies should be conducted considering various environmental factors.
In this study, one-quarter of the examined adolescents displayed smartphone overdependence, and it was more common in girls than boys. Many previous studies also reported sex differences in problems related to smartphone use [
13,
18], with more smartphone overdependence in girls than in boys [
18]. This was also in line with a 2020 survey on smartphone overdependence in South Korea, which reported that girls were relatively more vulnerable to smartphone overdependence than boys [
7]. This may be attributed to the higher probability of girls using their smartphones for peer communication via SNS, online chats, and internet browsing, whereas boys mostly use their smartphones for playing games [
5].
A considerable advantage of this study is the use of a smartphone overdependence screening tool with high reliability as the tool was developed by a national institution in South Korea. The fact that the tool was developed primarily for use in South Korea prevents a ready comparison with other countries. As smartphone overdependence is a relatively new phenomenon, the comparison among different countries is difficult. Even in the USA, a well-established scale for smartphone overdependence has not yet been established [
21]. In certain studies, the level of smartphone overdependence was measured based on the time of use to analyze the relationship with psychosocial variables [
5]; however, the determination of smartphone overdependence or addiction solely based on increased time of use does not seem reliable. In the future, a standardized tool should be applied to compare the status of different countries with subsequent discussions [
21].
In this study, smartphone overdependence in adolescents was correlated with depressive and loneliness symptoms, regardless of sex. The former result coincides with a previous study that found more depressive symptoms in adolescents with problematic smartphone use [
18], based on the same context in which depression was suggested as a predictor of problematic smartphone use [
13]. The latter result coincides with numerous previous studies that reported that self-perceived loneliness in adolescents has a significant effect on smartphone addiction [
4,
15]; higher levels of loneliness lead to higher problematic smartphone use [
3], and an increase in smartphone dependency leads to an increase in loneliness [
22]. This result is thus indicative of how smartphones may be used to compensate for the lack of social interactions [
17] and how loneliness may influence smartphone overdependence. Adolescents who perceive a high level of loneliness resort to the use of smartphones to overcome loneliness, which unintentionally causes daily problems; thus, the preference for the virtual reality experienced through smartphone use increases [
15]. One way to solve the problem of smartphone overdependence may be to reduce loneliness in adolescents by providing activities in which they participate in social interactions [
14,
17].
With the rapid distribution of smartphones in South Korea, the problem of social maladaptation caused by smartphone use has become a widespread social issue [
2,
11]. The problematic behaviors related to smartphone use are not being addicted to the device itself, but rather being addicted to the content that they provide [
10]. For adolescents, however, smartphone use is a means of communication and a crucial source of information; thus, it is extremely difficult to prevent their use altogether. To minimize the problems related to smartphone use, it is necessary to provide an environment for adolescents to reduce their levels of loneliness and depression. Effective social support and psychological guidance are likely to help adolescents use their smartphones in more reasonable and appropriate ways. Problematic smartphone use is also predicted to decrease through the promotion of the healthy use of SNS and positive social relationships [
13]. In the future, suitable social interventions and measures should be developed and applied to prevent smartphone addiction among adolescents.
Practitioners providing care for adolescents should consider the following. Firstly, with the understanding of the impact of depressive symptoms and loneliness on smartphone overdependence in adolescents, appropriate help should be provided to maintain good mental health. Practitioners should discuss smartphone use with adolescents to help clarify the relationships among smartphone use, dependence, and psychological health. Secondly, cellular phone distraction reduction application [
23] may be recommended to adolescents for them to manage their smartphone usage more effectively.
This study had a few limitations that inform future researchers. Firstly, this study presents results obtained during the special circumstances of the COVID-19 pandemic. Thus, the results should be compared with the future trends of changes concerning smartphone overdependence, depressive symptoms, and loneliness after the COVID-19 pandemic. Secondly, several relevant factors that were examined previously were not included in this study (e.g., shyness [
11], self-esteem [
22], and interpersonal relationships [
18]). Future researchers may wish to elaborate on these prior findings. Thirdly, the levels of depressive symptoms and loneliness were measured through students’ self-reported responses; thus, there is a possibility of under- or over-estimation owing to the lack of objective indicators. Notably, participants completed a measure of depression using a short-term timeframe. In future studies, depressive symptoms and loneliness should be measured more objectively, while their severity should also be analyzed.
The unique significance of this study lies in the fact that it was conducted in a situation where the global COVID-19 pandemic persists to restrict social interactions. One-quarter of adolescents displayed smartphone overdependence, which was more common in girls than boys. Students’ smartphone overdependence was influenced by depressive symptoms and loneliness, regardless of sex. Consequently, appropriate interventions and policies should be developed to resolve the problem of smartphone overdependence through the reduction of adolescents’ depressive and loneliness symptoms.