1. Introduction

Nearly 2 hours every day, or 5 years of the average person's life, are spent on social media. In addition, more than 200 million people in the world are influenced by the internet and social media disorder, and adolescents who spend more than 5 hours per day on social media are more easily influenced by depression. Therefore, social media addiction is a common social phenomenon nowadays [1]. A social media addict is someone who is extremely preoccupied with using social media, driven by an irresistible want to log on, and who spends so much time and energy on it that it interferes with other crucial aspects of their lives [2-3].

A study conducted by Berryman et al. examined the relationship between social media use and mental health [4]. It was concluded in this study that social media usage can cause loneliness and suicidal thoughts among other negative feelings, but it remains a poor predictor of mental health problems, although some certain behaviors can be considered as warning signs. A similar study has been conducted by the Greenwood Institute of Child Health and the University of Leicester. They conducted six focus groups on teenagers from 11-18 years old and analysed their mental health and their social media usage. The results show that social media is more likely to cause anxiety disorders for some adolescents and it is a platform for cyberbullying, and the symptoms of anxiety disorders are unlikely to be overlooked [5]. Shakya and Christakisexplored the relationship between the use of Facebook and individual well-being [6]. They found that using Facebook frequently negatively related to individual well-being. In addition, Simsek et al. conducted a comparative study on the social media addiction of high school and university students [3], and they collected data from 700 students and found both college students and high school students have a modest level of social media addiction, and whether a person is a student at a university or high school has little bearing on their level of addiction. However, gender, length of use, university department, and high school type all showed significant differences.

A study investigated the intersection of social media and the workplace. Scholars surveyed 326 full-time employees and found that social media addiction was positively related to employee work-family conflict and burnout and then reduced employee work performance [7].

These studies provide the literature and theoretical basis for us to discover the effects of social media addiction. However, the existing research has at least one research gap, that is, we little know that social media addiction causes adolescents’ mental health problems or it just happens to be another symptom of other diseases. In addition, these researches lack experiment of certain types of mental illness, such as depression, which we will mention in our study. Therefore, in our study, we will discuss the effects of social media addiction on depression and social phobia in adolescents in order to prompt society to pay attention to the outcome of adolescent social media addiction and take positive intervention measures.

2. Theory and Proposition

2.1. Social Media Addiction: Concept and Influences

Social media addiction (SMA) is a mental disorder that will cause exceptional concern about social media and irritation when individuals are unable to use it [8]. There are biological factors, psychological factors, and environmental factors that could lead to the development of social media addiction [9]. Usually, the patients do not seem to be addicted to the internet itself, but rather to certain activities. It also has a great impact on the family relationship when reality is neglected and people stop sharing secrets or information with their close friends in reality. In the last 10 years, a huge number of people have suffered from SMA, and it brings harm and burden to the individual level. But it still hasn’t been paid much attention to these years and it didn’t appear in the latest versions of The Diagnostic and Statistical Manual of Mental Disorders-V (DSM-V).

Scholars have found that social media addiction has a series of influences on an individual’s behavior and psychology [10-11]. For example, individuals have difficulty controlling their use of social media. In order to use social media, individuals often invest a lot of time and energy, which leads to poor work and study results. In addition, even if individuals know these negative outcomes, they cannot reduce their use of social media and must rely on continuous use to relieve their negative emotions. On the one hand, these behaviors and feelings reflect individuals’ overuse of social media. On the other hand, these behaviors and feelings also reflect the strong psychological dependence of individuals on social media. In summary, we propose that adolescents with social media addiction are usually unable to control themselves to use social media, which results in depression or social phobia.

2.2. Social Media Addiction and Adolescents’ Depression

Depression is a serious medical illness that causes feelings of sadness and a lack of interest in what you once enjoyed [12-13]. People with serious depression symptoms can also experience hallucinations and suicidal urges. We are supposed to feel happy when communicating with other people, but sometimes when we keep getting negative feedback, such as bullying or other negative emotions, and we are unable to pull away from this kind of unhappiness. It makes us to feel weak. Sometimes these negative emotions can stop us from doing other activities, and then we become too absorbed in the sadness. We propose that social media addiction is positively related to adolescents’ depression.

Specifically, on the one hand, social media addiction can cause adolescents to lose their hobbies in the real world and their interest in reality will decrease [13]. Their brains are accustomed to the surge of large amounts of dopamine that online activity provides, and the regular activity can no longer satisfy them. Over time, adolescents may lose enough enthusiasm for the real world to find it less fun, which eventually leads to depression. On the other hand, social media is full of information about other people’s life status, and a study from the University of Pennsylvania found that adolescents who engage in social comparison behavior on social media are also depressed when they find other people’s life status to be better and cooler over time. Based on this finding, we can argue that not only life status, but also when adolescents find themselves worse than others in many ways through social media over a long period of time, they become more depressed.

As a result of being addicted to social media, adolescents will gradually lose interest in real life and make a great deal of negative social comparisons, which may result in depression.

2.3. Social Media Addiction and Adolescents’ Social Phobia

Generally, social phobia involves an excessive and unreasonable fear of objects or situations outside of one’s control, although the individual is aware that the fear reaction is excessive or unreasonable, it continues to persist and is difficult to manage [14]. We propose that social media addiction is positively related to adolescents’ social phobia.

Specifically, on the one hand, social media provides adolescents with more diverse forms of interaction, such as the use of funny emoticons, which will encourage adolescents to rely on online forms of interaction. Long-term addiction to social media will gradually make adolescents lose the ability to communicate offline with high quality, which may make them unwilling to communicate and interact with others offline. Over time, they may become resistant to offline social communication; that is, social media addiction may positively relate to adolescents’ social phobia. On the other hand, interaction and communication in social media have a high fault tolerance rate. For example, when people send a wrong message, they can withdraw it in time, which will reduce people’s social communication costs. But offline, people do not have such opportunities. Once said, it is difficult to take back, which may also reduce the willingness of adolescents to interact offline, and even the fear of offline interaction [15]. Therefore, after being addicted to social media, adolescents may gradually lose their willingness to interact offline. In summary, when adolescents are addicted to social media, they will gradually lose interest in offline interaction because online interaction provides richer forms of interaction and has a higher fault tolerance rate [16], which will make adolescents gradually dependent on online interaction and lose the ability and willingness to engage in offline interaction. Therefore, we propose that social media addiction can lead to adolescents’ resistance and fear of offline interaction.

3. Conclusion and Discussion

3.1. Research Conclusion

At present, social media addiction is a common phenomenon in our daily lives. This study first summarizes the concept and connotation of social media addiction, then sorts out the influences of social media addiction on individuals, and finally proposes that social media addiction will have an impact on adolescents’ depression and social phobia.

3.2. Theorical Contributions

There are two theoretical contributions to this work. On the one hand, this study advances ideas about how social media addiction affects adolescent depression and its causes while also enhancing the mechanism by which it does so. However, this study refines the influence mechanism of social media addiction on teenagers' social phobia and further proposes the influence of social media addiction on adolescents' social phobia and its causes. Understanding these connections and causes can help us better comprehend how social media addiction affects teenagers.

3.3. Practical Value

This study has two practical values. First, society should pay more attention to adolescents’ social media addiction and take effective intervention measures to manage this social phenomenon. Especially for enterprises providing social media software, the time and frequency of adolescents’ use of social media should be detected and controlled under the intervention of the government and social organizations.

Second, for schools and parents, reasonable interventions should be carried out on adolescents’ use of social media. On the one hand, it is necessary to help adolescents understand the negative influences of social media addiction and urge them to be vigilant. On the other hand, adolescents should be guided to use social media to carry out healthy and positive social activities. When necessary, adolescents’ use of social media should be strictly monitored.

3.4. Limitations and Future Research Directions

This study has two limitations, which are worthy of further exploration by scholars. First, our study is a theoretical study, which only proposed the influence of social media addiction on adolescents’ depression and social phobia in theory and did not carry out empirical research. Scholars can empirically test the two relationships we proposed in future studies and enhance the persuasiveness and theoretical contribution of the study.

Second, What are the mediators of the effect of social media addiction on teenagers' depression and social phobia, as our study did not explicitly propose the internal mechanism of social media addiction affecting adolescents' depression and social phobia? For example, does social media addiction affect adolescents’ depression through reducing life satisfaction In future studies, scholars can refine the internal mechanism of the relationship we propose and conduct empirical tests [17].