Internet gaming disorder symptoms and functional impairment in a non‐clinical sample of adolescents and young adults in Japan

Internet gaming disorder (IGD) has attracted increasing attention as a potential mental health concern among adolescents and young adults.1, 2 IGD has also been reported to frequently co-occur with a range of psychiatric conditions.3 Although excessive game play time is often considered a core feature of problematic gaming, substantial debate remains regarding the extent to which time spent gaming alone reflects addictive behavior or clinically meaningful disorder, particularly in non-clinical populations.4 Symptom-based screening tools may therefore identify individuals with elevated gaming-related symptoms even in the absence of functional impairment. This approach allowed us to examine symptom severity across a broad range of gaming involvement. The present study examined the distribution of the ten-item internet gaming disorder test (IGDT-10)5, 6 scores and their associations with game play time, demographic characteristics, and functional impairment in a non-clinical sample of adolescents and young adults in Japan. This cross-sectional study used data from a nationwide online survey conducted by LINE Research Inc. LINE Research is one of the largest smartphone-based survey platforms in Japan, with a broad user base across demographic groups. A total of 420 individuals aged 15–29 years participated, equally stratified by age group (15–19 years, 20–29 years) and sex. The total sample (n = 420) was equally divided into four groups defined by age and sex (15–19 years/male, 15–19 years/female, 20–29 years/male, 20–29 years/female), with 105 participants in each group. Given the targeted age range (15–29 years), approximately two-thirds of participants were students. Among them, 337 participants (80.2%) who reported playing digital games at least once a week were included in the analyses. IGD symptoms were assessed using the IGDT-10, based on DSM-5 criteria.7 Symptom severity was evaluated using the modified version scoring method (IGDT-10-MV),8 in which responses of “sometimes” or “often” are counted as symptom endorsement, with a recommended cutoff of ≥5. Participants also reported their average daily game play time (<1 h, 1–3 h, 3–6 h, ≥6 h), age, sex, and occupational status (student or employed). Functional impairment related to gaming was defined as endorsement of either or both of the two IGDT-10 items assessing impairment (items 9 and 10) at the level of “often,” consistent with a single DSM-5 criterion. Because IGDT-10-MV scores were non-normally distributed, Spearman's rank correlation coefficient, the Kruskal–Wallis test, and the Mann–Whitney U test were used. Statistical significance was set at p < 0.05 (two-tailed). The study protocol was approved by the Ethics Committee of Tokiwa Hospital. Given the anonymous and non-interventional nature of the secondary data analysis, the requirement for written informed consent from individual participants was waived. IGDT-10-MV scores were significantly and positively correlated with daily game play time (Spearman's ρ = 0.36, p < 0.001). Comparisons across the four game play time categories showed a significant group difference (Kruskal–Wallis test, H = 46.06, df = 3, p < 0.001), with median IGDT-10-MV scores increasing progressively with longer game play time (Figure 1). Using the IGDT-10-MV cutoff, 128 participants (38.0% of game players) screened positive for elevated IGD symptoms. It should be noted that this figure reflects screening positivity based on a symptom-based instrument and does not indicate clinically diagnosed IGD. No significant differences in IGDT-10-MV scores were observed between participants aged ≤18 years and ≥19 years (p = 0.056), between those in their teens and twenties (p = 0.072), or between students and employed participants (p = 0.445). Functional impairment related to gaming was identified in 19 participants (5.6% of game players). Participants with functional impairment showed significantly higher IGDT-10-MV scores than those without impairment (Mann–Whitney U test, U = 556.0, z = 6.02, p < 0.001), with median scores of 8.0 and 3.0, respectively. Notably, several participants without functional impairment also exhibited relatively high IGDT-10-MV scores, indicating a dissociation between symptom severity and impairment in a subset of individuals. Based on the original IGDT-10 scoring method, the prevalence of probable IGD in the total sample was 3.6%. This prevalence is broadly consistent with estimates reported in previous studies.9 This study provides normative data on IGDT-10 scores in a non-clinical sample of adolescents and young adults in Japan and highlights a robust association between game play time and IGD symptom severity. At the same time, the results support previous concerns that gaming duration alone does not adequately capture clinically relevant disorder. Although more than one-third of game players screened positive for elevated symptoms using the IGDT-10-MV, only a small proportion exhibited functional impairment. Because the IGDT-10-MV is designed to maximize sensitivity in community settings, exceeding the cutoff indicates elevated symptomatology rather than a confirmed clinical diagnosis. Accordingly, the proportion of screening-positive participants should not be interpreted as the prevalence of IGD in the general population. The marked elevation of IGDT-10-MV scores among participants with functional impairment suggests that impairment represents a critical threshold distinguishing clinically meaningful disorder from subclinical symptomatology. These findings underscore the importance of incorporating functional impairment into screening and assessment frameworks for IGD, particularly when applying symptom-based instruments in community samples.10 Several limitations should be noted, including the cross-sectional design, small sample size, and reliance on self-report data. Furthermore, functional impairment was operationalized based on endorsement of two IGDT-10 items at the level of “often.” Although this approach approximates the DSM-5 criterion for clinically significant impairment, it captures only limited aspects of functioning and does not comprehensively assess impairment across academic, occupational, social, and family domains over time. In addition, participants were recruited through an online survey panel operated by LINE Research Inc., which may overrepresent individuals who are highly engaged with digital platforms and online activities, including gaming, while underrepresenting those with lower digital engagement or survey avoidance. Therefore, the distribution of IGDT-10-MV scores and the proportion of screening-positive participants observed in this study should be interpreted in light of potential selection bias. Despite these limitations, the present findings contribute to a clearer understanding of the continuum between gaming behavior, symptom severity, and functional outcomes in young people. The findings are most appropriately generalized to digitally active adolescents and young adults who participate in online survey panels, rather than to the entire youth population in Japan. Masaru Tateno: Writing—original draft; data curation; methodology; formal analysis; conceptualization. Akira Imamura: Writing—review and editing; methodology; project administration; funding acquisition. Takeshi Inoue: Writing—review and editing; conceptualization. Takanobu Matsuzaki: Writing—review and editing; conceptualization. Daisuke Jitoku: Writing—review and editing; conceptualization; supervision; funding acquisition. The authors would like to thank all the participants in this study and LINE Research Inc. for their support in participant recruitment through an online survey platform. The authors acknowledge editorial assistance by ChatGPT (OpenAI) in language polishing. All content decisions and verifications were made by the authors. The authors declare no conflict of interest. The study protocol was approved by the Ethics Committee of Tokiwa Hospital (TH-251215). Given the anonymous and non-interventional nature of the secondary data analysis, the requirement for written informed consent from individual participants was waived. N/A N/A The data that support the findings of this study are available from the corresponding author, Masaru Tateno, upon reasonable request. Requests will be considered on an individual basis based on ethical considerations and study requirements.