Although problematic online gaming (POG) and problematic Internet use (PIU) have become a significant public mental health problem, their definitions and diagnoses remain heterogeneous. In 2013, internet gaming disorder (IGD) was included in section three, “Conditions for further study,” of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) [1]. Of the non-substance addictive behaviors, only gambling disorder has been reclassified in the substancerelated and addictive disorders section. Although IGD shares common properties with substance use disorder and pathologic gambling, research on IGD is not yet sufficient to support the establishment of specific diagnostic criteria [2]. To clarify this complicated concept, a study on IGD risk factors and comorbidities was recommended [3].

There are several risk factors associated with POG and PIU. Older adolescents and young adult males were the most vulnerable groups associated with POG [4] and male gender is also considered to have a higher susceptibility to PIU [5]. In terms of cognitive function, intelligence and flexibility are associated with both POG and PIU [6,7]. In an adolescent study, lower selfesteem and satisfaction with daily life were associated with POG severity, but only in males [8]. In a hierarchical model that included gender, age, cognitive function, and social interaction, psychopathological conditions such as attention, mood, anxiety, and impulsivity were the strongest risk factors for POG [9]. Among the psychopathological conditions associated with POG, attention deficit/hyperactivity disorder (ADHD) has been suggested to be the most significant predictor of POG by both cross-sectional and prospective studies [10]. In a study of young adult college students, adult ADHD and depressive disorder were associated with PIU, but only in males [11]. In a systematic review of PIU and comorbid psychopathology, depression and ADHD symptoms showed the most significant and consistent correlations with PIU [12]. In a recent study of a representative sample of European adolescents, while PIU was associated with depression, POG was associated with male gender and peer problems [13].

Online gaming user experiences are associated with POG [14]. Witmer and Singer (1998) defined “presence” as the subjective experience of being in one place or environment, even when one is physically situated in another. The authors also developed a theoretical construct called “immersive tendency,” which relates to the tendency to become involved in a continuous stream of stimuli. While presence is an experiential concept, immersive tendency is a personality trait positively correlated with presence. It is the disposition to become involved in everyday activities, and the ability to focus on a particular activity. Immersive tendency is evaluated according to everyday activities, such as watching movies, reading novels, and dreaming, while presence is evaluated according to individual experiences in mediated environments. In a recent study with high-ranked game players, addicted gamers had higher immersive tendency than highly engaged, non-addicted players [15]. In concept, immersive tendency may be a specific risk factor for IGD independent of gaming context, such as a player’s motivation.

To our knowledge, no study has examined the relationship between immersive tendency and POG/PIU with comorbid psychopathologies such as ADHD and depression. The aim of the study was to investigate whether the direct relationship between immersive tendency and POG/PIU is mediated by ADHD symptoms.

This study was conducted with undergraduate students. To minimize the influence of confounding factors, we restricted our sample to a homogeneous population of male students, aged 19-29 years, from two high-ranking universities in South Korea (Seoul National University and Yonsei University). For another physiological experiment, we recruited 26 actively gaming and 29 control students. Several conditions were included as participant screening criteria: 1) a maladaptive preoccupation with both online and offline computer gaming; 2) severe suffering or impairment due to computer gaming; 3) a Young’s Internet Addiction Test (YIAT) score of more than 50 points [16]; and 4) more than four hours of computer gaming daily [17]. A psychiatrist interviewed the participants to assess for any Axis I psychiatric disorders that could lead to excessive computer usage, such as mania, hypomania, or a substance-related disorder. The psychiatrist rated the severity of participants’ depression using the Montgomery-Åsberg Depression Rating Scale, to exclude participants with significant depression [18]. One participant was diagnosed with bipolar disorder and ADHD, and excluded on this basis. Another participant was excluded because he was receiving treatment for narcolepsy with stimulant medication. Two participants were excluded as they returned incomplete questionnaires. In total, the analysis was conducted with 51 male undergraduate students; 23 active gamers and 28 control participants. Written consents were obtained from participants before the experiment.

The Institutional Review Board of the Seoul National University Hospital approved the study protocol (IRB 1101-090-349), and we obtained written informed consent from each participant.

All participants were of Korean ethnicity. Ages ranged from 19 to 29 years, and the mean age was 23.1 years (SD=2.4) (Table 1). Immersive tendency scores had a wide range, from 13 to 94, considering the possible range of 0 to 108. The mean score was 50.0 (SD=17.0). Although the psychiatric interviews were performed to exclude participants with any major psychiatric conditions, the adult ADHD subscales identified significant problems affecting 5.9-11.8% of the participants. However, no participants scored higher than the cutoff scores on all the three adult ADHD subscales. Of the 51 participants, six (11.8%) reported childhood ADHD symptoms, and two had no significant problems according to the current ADHD subscales. Eighteen (35.3%) were classified as the POG group. According to the different PIU ratings, 12 (23.5%) were classified as the PIU group, and 10 participants showed significant POG and PIU problems.

There was no significant difference in age between the active gamers, who played online games more than hours a day, and the control students (Table 2). Active gamers had higher scores in immersive tendency, ADHD symptoms, POG, and PIU than the control group.

As shown in Table 3, immersive tendency had a significant relationship with ADHD, POG, and PIU.

The current study presents, to the best of our knowledge, the first report demonstrating that the association between immersive tendency and POG/PIU is mediated by ADHD symptoms. Although the association between ADHD and POG/PIU has been investigated, there are few studies on the effect of immersive tendency symptoms, and no studies have observed immersive tendency and ADHD simultaneously. This study found that current ADHD symptoms, especially inattention, mediate the effect of immersive tendency on POG/PIU, which explains the mediation model better than ADHD symptoms during childhood.

Within online gaming, the motivations of players differ from one another and depend on personal factors [29]. In a study with massively multi-player online gamers, those who play for immersion motivation showed association with PIU [30]. The immersion motivation consists of discovery, role-playing, customization and escapism.

In a recent study on differences between addicted gamers and engaged players, the immersion motivation showed significant group difference [31]. However, the immersion motivation in those studies was evaluated on gaming experiences. Therefore, motivation could not be evaluated before game exposure. On the contrary, the immersive tendency questionnaire measures differences in personal tendencies toward presence through engagement in everyday activities, such as watching movies and television programs, reading books, and dreaming [19]. In a previous study on the differences between gaming addiction and high gaming engagement, addicted gamers scored higher on the immersive tendency questionnaire than highly engaged gamers [15]. However, the study did not evaluate other comorbid conditions, such as depression and anxiety. In the present study, the psychiatrist interviews and depression ratings excluded participants with comorbid conditions. Therefore, the study can more clearly explain the role of immersive tendency as a specific risk factor for POG/ PIU. Moreover, gamers who score high on immersive tendency are absorbed and immersed in computer games through not only spatial presence, but also “flow,” the sensation of being involved in gaming action [32]. Through these processes, a person with higher immersive tendency can experience the more hedonic effect of Internet gaming.

According to genetic evidence and stimulant-response studies, ADHD is a subtype of reward deficiency syndrome with dysfunction in the brain reward cascade such as in the dopamine system [33]. From childhood to adulthood, ADHD is associated with both the initiation and persistence of habit-forming illnesses, such as alcohol dependence and substance addiction [34]. Moreover, the association between ADHD and addiction is not limited to substances. Sustained ADHD throughout childhood and young adulthood increases the severity of gambling problems [35]. The relationship between ADHD and gaming addiction has emerged from evidence on comorbidity, common mechanisms, and genetic associations [10]. Patients with ADHD play an internet game, which releases dopamine, for self-medication like other addictive substances [36]. A person with higher immersive tendency may have a more exaggerated dopamine release in a virtual gaming environment, which makes internet gaming more addictive. Patients with higher immersive tendency might be more susceptible to internet gaming, and this susceptibility may be mediated by ADHD.

In addition, a previous study recorded that excessive online gamers experience biological changes in the ECG and respiratory systems, compared to a control group with similar demographic conditions [17]. The findings from this study revealed a conditional subordinate relationship between central inhibitory and autonomic responses, which result in excessive gaming when experiencing pleasurable online stimuli. Additional methods could be conducted spontaneously to provide a more solid background to the findings from present study.

The present study has several limitations. First, the small number of participants in a highly homogenous social group, active gamers, may not sufficient to generalize the findings. To minimize possible confounding effects, we applied tightly controlled conditions. Although most studies have focused on children and adolescents, the prevalence of problematic gaming is also high in young adults, especially males [37]. To generalize the results of the present study, further studies that recruit a larger number of participants to cross-check the relationship between diverse demographic factors such as age, gender, education level are required.

Second, the present study did not investigate other comorbid psychopathologies, such as depression and anxiety. Immersive tendency may be a common risk factor for IGD, and depression can mediate the effect of the immersive tendency on IGD. A third limitation of the present study is that at the time of writing, there is no standard assessment instrument for IGD. Three POG/PIU scales were used to address this problem.

We observed the mediating effect of ADHD on the association between immersive tendency and IGD. It has been documented that ADHD symptoms must be controlled to treat IGD. We cautiously suggest that immersive tendency be evaluated as a factor that increases individual susceptibility to IGD.