Psychological Assessment 2015, Vol. 27, No. 2, 567-582 © 2015 American Psychological Association 1040-3590/15/$ 12.00 http://dx.doi.org/10.1037/pas0000062 The Internet Gaming Disorder Scale Jeroen S. Lemmens and Patti M. Valkenburg University of Amsterdam Douglas A. Gentile Iowa State University Recently, the American Psychiatric Association included Internet gaming disorder (IGD) in the appendix of the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The main aim of the current study was to test the reliability and validity of 4 survey instruments to measure IGD on the basis of the 9 criteria from the DSM-5: a long (27-item) and short (9-item) polytomous scale and a long (27-item) and short (9-item) dichotomous scale. The psychometric properties of these scales were tested among a representative sample of 2,444 Dutch adolescents and adults, ages 13-40 years. Confirmatory factor analyses demonstrated that the structural validity (i.e., the dimensional structure) of all scales was satisfactory. Both types of assessment (polytomous and dichotomous) were also reliable (i.e., internally consistent) and showed good criterion-related validity, as indicated by positive correlations with time spent playing games, loneliness, and aggression and negative correlations with self-esteem, prosocial behavior, and life satisfaction. The dichotomous 9-item IGD scale showed solid psychometric properties and was the most practical scale for diagnostic purposes. Latent class analysis of this dichotomous scale indicated that 3 groups could be discerned: normal gamers, risky gamers, and disordered gamers. On the basis of the number of people in this last group, the prevalence of IGD among 13- through 40-year-olds in the Netherlands is approximately 4%. If the DSM-5 threshold for diagnosis (experiencing 5 or more criteria) is applied, the prevalence of disordered gamers is more than 5%. Keywords: gaming disorder, game addiction, pathological gaming, Internet addiction, video games The Diagnostic and Statistical Manual o f Mental Disorders (. DSM) is used by psychiatrists and psychologists in many coun- tries as the main diagnostic tool for classifying psychiatric disor- ders. In the latest version of the DSM (5th ed. [DSM-5]), the American Psychiatric Association (APA) applied some changes to the descriptions and criteria for pathological behaviors and in- cluded Internet gaming disorder as a tentative disorder in the appendix of this manual (APA, 2013). The introduction of Internet gaming disorder in the DSM-5 represents a major advance for the study, treatment, and prevention of problematic and pathological use of computer and video games. The crucial next step is to develop a survey instrument to measure Internet gaming disorder with solid psychometric properties that can be used for research and diagnostic purposes. Therefore, the main aim of the current study was to develop a valid and reliable survey instrument for Internet gaming disorder on the basis of the nine underlying criteria from the DSM-5. Because this instrument should be ap- plicable to game-playing individuals of all ages, its properties were extensively tested among a representative sample of adolescents and adults (ages 13-40 years). This article was published Online First January 5, 2015. Jeroen S. Lemmens and Patti M. Valkenburg, Amsterdam School of Communication Research, University of Amsterdam; Douglas A. Gentile, Department of Psychology, Iowa State University. Correspondence concerning this article should be addressed to Jeroen S. Lemmens, Amsterdam School of Communication Research, University of Amsterdam, Nieuwe Achtergracht 166, 1001 NG, Amsterdam, the Neth- erlands. E-mail: j.s.lemmens@uva.nl Over the last decade, many efforts have been made to define and measure the concept of pathological involvement with computer or video games. Although playing video games is not considered intrinsically pathologic or problematic, gaming can become path- ological for some players when the activity becomes dysfunc- tional, harming an individual’s social, occupational, family, school, and psychological functioning (Gentile et al., 2011). In general, pathological gaming can be described as persistent, re- current, and excessive involvement with computer or video games that cannot be controlled, despite associated problems (Griffiths, 2005; Lemmens, Valkenburg, & Peter, 2009). Although game addiction is the most popular term to describe this disorder, this term is also considered ambiguous, because many players, devel- opers, and reviewers use the term addictive as a positive adjective, indicating the enduring playability of a game and not destructive or pathological behavior (Adams, 2002). Most studies on game ad- diction or similar constructs have adapted the definition and cri- teria for pathological gambling from the DSM-IV (APA, 2000), and many have therefore applied the term pathological gaming to this type of behavior (e.g., Chiou & Wan, 2007; Gentile, 2009; Johansson & Gotestam, 2004; Keepers, 1990; Lemmens, Valken- burg, & Peter, 201 la,201 lb). After careful consideration by a multidisciplinary expert workgroup, the APA decided on the ten- tative term Internet gaming disorder in the DSM-5 (Petty & O’Brien, 2013). Therefore, this term (or its abbreviation, IGD) and its underlying nine criteria will be used when addressing the measures under investigation in the current study. The DSM-5 states that only the use of Internet games must cause clinically significant impairment to constitute a diagnosis for IGD, not the use of sexual Internet sites, online gambling, or any other kind of Internet use (APA, 2013). Although the disorder is 567