Working Title: The Development and Psychometric Evaluation of the Internet Disorder Scale (IDS-15). Short Title: Development of the Internet Disorder Scale (IDS-15). Authors:

Introduction: Previously published research suggests that improvement in the assessment of Internet addiction (IA) is paramount in advancing the field. However, little has been done to address inconsistencies in the assessment of IA using a more updated framework. The aim of the present study was to develop a new instrument to assess IA based on a modification of the nine Internet Gaming Disorder (IGD) criteria as suggested by the American Psychiatric Association in the latest (fifth) edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), and to provide a taxonomy of the potential risk of IA risk among participants. Methods: A heterogeneous sample of Internet users (n=1,105) was recruited online (61.3% males, mean age 33 years). Construct validity of the new instrument – Internet Disorder Scale (IDS-15) – was assessed by means of factorial, convergent, and discriminant validity. Criterionrelated validity and reliability were also investigated. Additionally, latent profile analysis (LPA) was carried out to differentiate and characterize Internet users based on their potential IA risk. Results: The construct and criterion-related validity of the IDS15 were both warranted. The IDS-15 proved to be a valid and reliable tool. Using the LPA, participants were classed as “low addiction risk” (n = 183, 18.2%), “medium addiction risk” (n = 456, 41.1%), and “high addiction risk” (n = 455, 40.77%). Furthermore, key differences emerged among these classes in terms of age, relationship status, cigarette consumption, weekly Internet usage, age of Internet use initiation, and IDS-15 total scores. Conclusions: The present findings support the viability of using adapted IGD criteria as a framework to assess IA.