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. 2021 Oct 12;27(2):1000–1009. doi: 10.1038/s41380-021-01315-7

Table 1.

Characteristics of included studies.

Study (first author, year) Geographic area Age category Gender mix PUI definition PUI type Control definition PUI Control
N Mean age (SD) % M N Mean age (SD) % M
Choi et al. (2017) [33] South Korea Adults Male only Males in their 20 and 30 s who mostly played League of Legends, FIFA, or Sudden Attack; fulfilled the proposed DSM criteria. IGD Non-gaming users 22 29.5 (4.7) 100 24 27.2 (4.9) 100
Han et al. (2012) [34] South Korea Youth Male only YIAT > 50; game play time >4 h/day/30 h/week; impaired behaviors or distress OGA Healthy comparison group; game play time <3 h/day and <3 day/week 20 20.9 (2.0) 100 18 20.9 (2.1) 100
Horvath et al. (2020) [35] Germany Youth Mixed Smartphone owners aged 18–30 expressing interest in a study of “dysfunctional smartphone use”; SAS-SV > 31 (males), >33 (females) SPA Smartphone owners aged 18–30 expressing interest in a study of “dysfunctional smartphone use”; SAS-SV below cut-off 22 22.5 (3.0) 32 26 23.0 (3.2) 31
Jin et al. (2016) [36] China Youth Mixed Participated in online games such as League of Legends as major online behavior; fulfilled proposed DSM criteria; YIAT > 50 IGD Healthy control group with Internet use; participated in online games such as League of Legends as major online behavior; YIAT 20–30 25 19.1 (1.1) 64 21 18.8 (1.8) 67
Ko et al. (2015) [37] Taiwan Youth/ Adultsa Male only IGD diagnosis for >2 years according to DCIA; participated in online gaming for an average of ≥4 h/day on weekdays and ≥8 h/day on weekends IGD Never fulfilled DCIA 30 23.6 (2.5) 100 30 24.2 (2.5) 100
Lee, Namkoong et al. (2018)b [50] South Korea Youth/ Adultsa Male only YIAT > 50; reported gaming as the primary purpose of their Internet use; fulfilled proposed DSM criteria IGD Healthy controls; YIAT < 50; spent <2 h/day on online gaming 31 24.0 (2.6) 100 30 23.0 (2.8) 100
Lee, Park et al. (2018)c [38] South Korea Youth Male only YIAT ≥ 50; reported main use of Internet was playing games; clinician-administered interview to assess the core components of addiction IGD Healthy controls 45 23.8 (1.5) 100 35 23.4 (1.7) 100
Lin et al. (2015) [39] China Youth Male only YIAT ≥ 50; reported “spending most of their online time playing online games (>50 %)” IGA Healthy controls 35 22.2 (3.1) 100 36 22.3 (2.5) 100
Seok and Sohn (2018) [40] South Korea Youth Male only Fulfilled proposed DSM criteria IGD Healthy controls 20 21.7 (2.7) 100 20 22.4 (2.6) 100
Sun et al. (2014) [41] China Youth Mixed Fulfilled modified YDQ criteria; subjects characterized as the IGA subtype (mostly focused on online gaming when using the Internet) IGA Healthy controls; sometimes played online/mobile games but did not meet diagnostic criteria for IGAd 18 20.5 (3.6) 83 21 22.0 (2.4) 86
C. Wang et al. (2021) [42] China Youth Mixed YIAT ≥ 50; fulfilled ≥ 5 proposed DSM criteria IGD Healthy controls; YIAT < 50; fulfilled <5 proposed DSM criteria; never played online games or spent <2 h/day playing online games in the last 2 yearsd 26 23.2 (2.5) 54 28 23.4 (2.8) 54
S. Wang et al. (2018)c [43] China Youth Male only Fulfilled ≥ 5 proposed DSM criteria; YIAT ≥ 50; reported Internet gaming as primary online activity IGD Normal controls; fulfilled <4 proposed DSM criteria; YIAT < 30 48 20.6 (1.0) 100 32 21.1 (2.2) 100
Y. Wang et al. (2016) [44] China Youth Mixed MPAI > 51 MPD Non-MPD 34 21.6 (2.1) 38 34 21.7 (1.9) 38
Z. Wang et al. (2018)c [45] China Youth Mixed Regularly played “League of Legends” for at least a year; fulfilled ≥ 5 proposed DSM criteria; YIAT ≥ 50 IGD Recreational game users; regularly played “League of Legends” for at least a year and as frequently as the IGD subjects (at least 5/7 days and >14 h/week); fulfilled <4 proposed DSM criteria; YIAT < 50 38 20.7 (2.1) 71 66 21.3 (2.0) 56
Weng et al. (2013) [46] China Youth Mixed Fulfilled modified YDQ criteria; playing online games was the primary Internet activity OGA Healthy individuals without OGA 17 16.3 (3.0) 24 17 15.5 (3.2) 12
Yoon et al. (2017) [47] South Korea Youth/ Adultsa Male only Fulfilled proposed DSM criteria; YIAT ≥ 50; spent > 4 h/day and > 30 h/week involved in Internet gaming IGD Healthy controls; used the Internet <2 h/day 19 22.9 (5.2) 100 25 25.4 (3.8) 100
Yuan et al. (2011) [48] China Youth Mixed Fulfilled modified YDQ criteria IAD Healthy controls; spent <2 h/day on the internet 18 19.4 (3.1) 67 18 19.5 (2.8) 67
Zhou et al. (2011) [49] China Youth Mixed Fulfilled modified YDQ criteria IA Healthy individuals sometimes played games but did not meet diagnostic criteria for IAd 18 17.2 (2.6) 89 15 17.8 (2.6) 87

DCIA diagnostic criteria for Internet addiction, DSM Diagnostic and Statistical Manual of Mental Disorders (5th ed.), IA Internet addiction, IAD Internet addiction disorder, IGA Internet gaming addiction, IGD Internet gaming disorder, M male, MPAI mobile phone addiction index, MPD mobile phone dependence, OGA online game addiction, PUI Problematic Usage of the Internet, SAS-SV short version of the Smartphone Addiction Scale, SPA smartphone addiction, YDQ Young’s diagnostic questionnaire, YIAT Young’s online Internet addiction test.

aMean ages reported in the two samples fell into both the Youth and Adults categories.

bIncluded in the voxel-based morphometry meta-analysis but not in secondary analyses.

cSurface-based morphometry studies included only in secondary analyses.

dIncludes information from unpublished sources.