Reply to reviewersReviewer #1 Comment 1: The aim of the study was to investigate the relationships between Problematic Internet Use (PIU) and time spent online, online activities and psychopathology, by taking cross-cultural and gender differences into account. Additionaly it was aimed to explore the prevalence of PIU among European Internet users according the 5593 responding internet users. The topic is timely and interesting.It is not clearly explained if problematic gaming, gambling and pornography are subdimensions of Problematic Internet Use (PIU) or different independent variables. Answer 1:We provided some additional information on page 1: "Therefore, PIU represents generalized PIU (Davis, 2001) and can include several specific uses, such as online gaming, gambling or pornography use (Laconi, Tricard, & Chabrol, 2015).".Comment 2: Which gap in the literature will be filled through this research, in other words what is the value added to the literature by this paper?Answer 2: We added additional information regarding this thanks to this comment, as follows: "Cross-cultural studies allow a better understanding of results given the use of the same methodology, timeline or statistical analysis. However, few cross-cultural studies have been performed on PIU, despite it being an international health issue. To our knowledge, only one cross-cultural study explored PIU among 989 adults of four European countries (Sariyska et al., 2014), the others being focused on adolescents, and none exclusively among European users. PIU has been the subject of many studies since the last decade, but there is a need for cross-cultural empirical research.". Comment 3: The possible reasons of the differences between countries based on the results of the study need to explained.Answer 3: More explanation has been provided in the discussion section and the second paragraph of this section begins by "Apart from the question of whether PIU as a phenomenon is on the increase, it is fascinating that comparing the countries we investigated, startling differences in the numbers of problematic users were found. Further research is *Response to Reviewers needed to determine whether a stable pattern emerges and what the reasons for these differences may be.".Besides, in the limitations section, we added: "Cultural background may be a weaker predictor of online behavior than age of onset for Internet use or participation in specific online communities. It can be argued that the Internet is facilitating the spread of new trends worldwide at a much faster rate than before, but also that it creates an international community in its own right, which is evident with the community of online gaming or social media.". Comment 4: The conclusion part is not satisfactory, also implications are missing. Answer 4:The conclusion has been modified. As all the reviewers suggested, an Implication section has been added.Comment 5 : Although the researchers tried to sample all ages, 2/3 of it is university students which can dominate the sample and may lead to ...

Objectives: The nine-item Problematic Internet Use Questionnaire (PIUQ-9) is a brief self-report screening instrument for problematic internet use. The main objective of the present study was to explore the psychometric properties of the PIUQ-9 among nine different language-based samples of European internet users (Italian, German, French, Polish, Turkish, Hungarian, English, and Greek). Methods: The total sample comprised 5,593 internet users (38.1% men), aged between 18 and 87 years ( M = 25.81; SD = 8.61). Via online recruitment, participants completed the PIUQ-9, the Brief Symptom Inventory (BSI) and items about time spent online. Results: Confirmatory factor analysis demonstrated that the bifactor model with one general factor (i.e., general problem) and two-specific factors (i.e., obsession and neglect + control disorder) yielded acceptable or good fit indices in all subsamples except for one. The common variance index in the bifactor model indicated that the general problem factor explained from 57.0 to 76.5% of common variance, which supports the presence of a strong global factor. According to the multiple indicators multiple causes (MIMIC) model, psychiatric symptoms had a moderate-to-strong direct effect on the general problem factor in all subsamples, ranging from β = 0.28 to β = 0.52 supporting the construct validity of the scale. Furthermore, in a majority of the subsamples, time spent online during the weekend had considerably higher effect sizes on the general problem factor than time spent online during weekdays. Conclusion: The present study highlights the appropriate psychometric properties of the PIUQ-9 across a number of European languages and cultures.

Background and aimsInternet Gaming Disorder is included in the Diagnostic and statistical manual of mental disorders (5th edition) as a disorder that merits further research. The diagnostic criteria are based on those for Substance Use Disorder and Gambling Disorder. Excessive gamblers and persons with Substance Use Disorder show attentional biases towards stimuli related to their addictions. We investigated whether excessive Internet gamers show a similar attentional bias, by using two established experimental paradigms.MethodsWe measured reaction times of excessive Internet gamers and non-gamers (N = 51, 23.7 ± 2.7 years) by using an addiction Stroop with computer-related and neutral words, as well as a visual probe with computer-related and neutral pictures. Mixed design analyses of variance with the between-subjects factor group (gamer/non-gamer) and the within-subjects factor stimulus type (computer-related/neutral) were calculated for the reaction times as well as for valence and familiarity ratings of the stimulus material.ResultsIn the addiction Stroop, an interaction for group × word type was found: Only gamers showed longer reaction times to computer-related words compared to neutral words, thus exhibiting an attentional bias. In the visual probe, no differences in reaction time between computer-related and neutral pictures were found in either group, but the gamers were faster overall.ConclusionsAn attentional bias towards computer-related stimuli was found in excessive Internet gamers, by using an addiction Stroop but not by using a visual probe. A possible explanation for the discrepancy could lie in the fact that the visual probe may have been too easy for the gamers.

With the inclusion of Internet Gaming Disorder (IGD) in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders comes the need for a reliable and valid questionnaire to assess the diagnosis. The Internet Gaming Disorder Questionnaire (IGDQ) is a short tool that measures IGD. Our study aimed at investigating its psychometric properties in a sample of German gamers. Eight hundred ninety-four Internet game players (mean age: 26.5 ± 8.5 years, range: 18-75 years, 87.36% male) completed an online version of the IGDQ and the Compulsive Internet Use Scale (CIUS) and provided information on their Internet and gaming use. Item and reliability analyses were computed. To investigate the component structure, the sample was randomly divided into two subsamples. A maximum likelihood factor analysis was conducted for one subsample and a confirmatory factor analysis (CFA) for the other subsample. The IGDQ had a Cronbach's alpha of 0.70. The IGDQ score correlated with the CIUS score (r = 0.59) and the time spent playing (r = 0.24). The maximum likelihood factor analysis extracted one component, explaining 30.26% of the variance, which was confirmed by the CFA. The correlation of the IGDQ score with the CIUS score is a first indicator that the IGDQ allows for valid interpretations. In all, 7.94% of the gamers met the criteria for IGD.

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