In recent years, internet addiction has been regarded as an increasingly significant public health issue. A range of studies have demonstrated that a high prevalence of internet addiction in adolescents and young adult population is associated with evident psychiatric problems and serious functional impairment [1–4]. In Greek, Siomos et al’s study revealed that 8.2% of 2200 adolescent students aged between 12 to 18 had meet the criteria of the Diagnostic Questionnaire for Internet Addiction [4]. In US, Christakis et al. assessed 307 college students at two US universities using the Internet Addiction Test and the Patient Health Questionnaire, noting that 4% of students scored in the problematic or addicted range, and identifying a significant association between problematic internet usage and moderate to severe depression [2]. Among 50 adult patients with internet addiction, Bernadi et al. observed that 14% had a diagnosis of attention deficit and hyperactivity disorder, 15% generalized anxiety disorder, 15% social anxiety disorder, and 7% dysthymia [5]. In Taiwan, Tsai et al. identified 17.9% of university students meet the criteria of internet addiction group using the Chinese Internet Addiction Scale-Revision (CIAS-R), and the risk factors included male gender, habit of skipping breakfast, mental health morbidity, deficient social support, and neurotic personality traits [6].

The technology of online gaming has rapidly developed within the past decade, with online games becoming one of the major daily entertainments for millions of people. Prior research identified that, among the internet activities, online gaming plays an important role on internet addiction, associating with poorer prognosis and more severe social impairments [7]. Griffiths et al. reported that 80% of online gamers sacrificed at least one element of their lives, such as sleep, work, education, and socializing with friends, family, and partners, to play online games. The younger the players, the longer the time they dedicated to playing online games, associating with the further functional impairment [8]. There are four main attractions to online gaming. First, the original game design: the soundtrack, frames, background story, and the complexity of the gaming elements. Second, the role playing achievements: the online gamers may experience new virtual roles, gaining satisfaction from building up characters within levels, accumulating online resources, experiencing online adventures, and receiving online rewards. Third, online social interactions: the gamers may form virtual relationships, gaining online friends, lovers, virtual business, and conducting other types of online activities. Fourth, psychological needs and motivations: online games provide players with outlets for unsatisfying needs and motivations in the real life; within the online game world, players can acquire those they are seeking in the real life, most of the times in an easier way, which motivates them to keep on gaming [9]. The craving for online gaming and substance dependence may share similar neurobiological mechanisms, thus inducing analogous behavioral effects such as excessive usage, severe withdrawal symptoms, tolerance, and negative repercussions [10]. Although there are many previous related studies on internet addiction, but few studies specifically focus on the online gaming and associated psychiatric problem. The aim of this study was, therefore, to investigate the characteristics of online gamers and the association between online gaming hours, social phobia, and depression, using an internet survey.

Our results showed a positive correlation between weekly online gaming hours and internet addiction symptom. The results were consistent with Ko et al.'s study showing a positive correlation between total online gaming hours and total CIAS score, indicating that excessive use of online games resulted in higher risk of internet addiction, leading to more functional impairment, including failure to fulfill obligations at work, school, and home, and decreased participation in social or recreational activities [13].

Our results also showed a positive correlation between online gaming hours and depressive symptom (DSSS-Depressive Subscale), somatic symptom (DSSS-Somatic Subscale), and Pain symptom (DSSS-Pain Subscale). The association of depressive symptoms was consistent with the findings of Schimit et al.’s study that subjects with online video game dependency spent longer hours per week playing games, had higher scores for loneness or isolation, higher scores for depression, lower scores for social belonging in real life, lower scores for self-esteem, and reduced ability to cope with emotional problems compared with those without dependency [16]. In Achab et al.’s study comparing the characteristics of addict vs non-addict online gamers, these addicted gamers self-reported significantly higher rates (3 times more) of irritability, daytime sleepiness, sleep deprivation due to play, low mood and emotional changes since online gaming onset [17]. Furthermore, self-reported negative consequences of computer game playing increased strongly with average daily playing time and the prevalence of sleeping problems, depression, suicide ideations, anxiety, and obsessions/ compulsions increased with increasing playing time in Wenzel et al.’s study [15]. Previously, investigators have proposed that subjects with depression use the internet excessively as a means of self-medicating, and that internet addiction itself could also cause depressive symptoms. Internet addiction and depression may share similar risk factors, such as environment, genes, education, or stress-coping skills, and each might serve to exacerbate the severity of the other [18]. In terms of personality traits, previous studies identified that individuals with online game addiction, especially the Massive Multiplayer Online Role Playing Games (MMORPG), had more aggressive and narcissistic tendencies, less self-control, fewer real world achievements, and lower self-esteem than normal individuals [19]. However, further investigation is needed to elucidate the common mechanisms underlying internet addiction and depression.

For the association of online gaming hours and somatic/pain symptoms, it might be explained that excessive game-playing leaded to muscle soreness, dry eyes, sleep deprivation, inadequate exercising, and even changes in dietary habits [20]. However, previous studies had shown the patients with depression had more somatic and pain symptoms. Half the depressed patients reported multiple unexplained somatic symptoms, and denied psychological symptoms of depression on direct questioning [21]. Some previous studies have suggested that patients in non-Western countries are more likely to report somatic symptoms than are patients in Western countries. The presence of any physical symptom increased the likelihood of a diagnosis of a mood or anxiety disorder by at least twofold to three-fold [22]. These online gamers might not identify their depression, but feel many somatic symptoms such as headache, chest tightness, and muscle pain to make them can't focus on school or work, and just spent much time on online game. For the clinical implication, the online gamer who complain many somatic and pain symptoms, we should pay attention to the possibility of depression.

Our results also demonstrated a positive correlation between online gaming hours and social anxiety symptoms by SPIN score. These results suggest that players who suffer from social phobic symptoms are more likely to indulge in the virtual reality provided by online games to avoid real life face to face social distress. Previous studies had shown the individuals with internet addiction had psychopathological characteristics of low self-esteem, low self-perception, and low confidence, but this social detachment in internet could result in further interpersonal frustrations in players’ real lives [23–25]. Achab et al. demonstrated online gamers with positive dependence Adapted Scale had more social, financial, marital, family, and/or professional difficulties since they started online gaming [17]. These findings highlighted the importance of identifying the problem of social anxiety/phobia when treating excessively using online gamers.

Another interesting finding is the gender difference. In our present study, 121 (16.8%) of the participants were female, with similar ages, years of education, and CIAS scores to the male online gamers. Females form a smaller proportion of the online gaming population. They also had shorter histories of online gaming and shorter weekly online gaming hours, but had more severe somatic, pain, and social phobic symptoms than the male players. The regression model also indicated the female gender is a predictor of depression according to DSSS score. Actually the gender difference has been identified in previous studies of substance addiction. Tuchman et al. reported gender differences in motivations for substance abuse, with females more likely to use illicit drugs for self-medication of depression or as a means of coping with stressful life events [26]. Women with substance-use problems are with more familial circumstances such as domestic violence, over-responsibility and divorce as high impact factors that lead to drug abuse [27]. Among 425 undergraduate students with problematic internet use, Hetzel-Riggin et al. reported that depression, keeping to oneself, and decreased tension increased problematic internet use in female online gamers [24]. In general, the majority of online gamers were males, these female online gamer had shorter histories of online gaming and shorter weekly online gaming hours, but had more severe somatic, pain, and social phobic symptoms than the male players. The results indicated these female players tend to engage in online games as a means of coping with depression, somatic symptoms, pain symptoms, and social anxiety. From the clinical point of view, the female online gamer might be with higher risk of depression.

To our best knowledge, this is the first study to investigate excessive online game hours and its association with depressive, social phobic, and internet addiction symptoms. However, there were some limitations. First, the enlisting of study subjects via invitation from online gaming websites introduces selection bias, thus the validity of their responses cannot be ensured. Second, the study is a descriptive, cross-sectional study. A prospective study would have represented a more meaningful means of evaluating the causal relationship between long hours spent playing online games and depression, social phobia, and internet addiction. Third, diagnoses of internet addiction, depression and social phobia could not be confirmed through self-completed questionnaires. Further investigation by face-to-face interview is needed to validate the findings. Fourth, the positive correlation between time spent on gaming and the internet addiction scale may be different for the subgroup of people with highly skilled hobbies or professions. In our survey, we didn’t identify this factor, and it deserves further research.

In conclusion, in the study population, online gamers who played excessively had higher incidence of comorbidities including internet addiction, depression, and social phobia. Depressive symptoms increased in severity with longer weekly online gaming hours, female gender, and severity of social phobia symptoms. These findings could prove useful when devising future strategies for prevention and intervention of problematic online gaming habits.