Background: Conceptualising internet addiction and assessing its symptoms has presented a significant challenge for researchers over the past 25 years. Recently, the Internet Disorder Scale (IDS-15), which is based on the criteria for Internet Gaming Disorder (IGD) from DSM-5, has emerged as a promising instrument to assess internet addiction. The main objective of the present study was to evaluate the psychometric properties of the Slovenian IDS-15.
Methods: The sample was recruited from the National Survey on the Use of Tobacco, Alcohol and Other Drugs that was conducted in 2018 on a nationally representative sample (N = 16,000; age range: 15-64 years; 62.4% response rate). The final sample comprised 9,161 participants, with 80.9% reporting having used the internet at least once a week (n = 7,413). A structured questionnaire was designed and internet addiction was assessed using the IDS-15.
Results: Confirmatory Factor Analysis showed acceptable fit to the proposed four-factor structure of the IDS-15. The reliability, and criterion, convergent and discriminant validity were also found to be adequate with a notable exception of the first item of the scale, as shown by its lower factor loading and higher variability. Additionally, latent profile analysis was used to distinguish between internet users with low (n = 3,818; 51.5%), medium (n = 3,111; 42.0%) and high (n = 484; 6.4%) addiction risk. Furthermore, the high-risk class was associated with higher IDS-15 factor scores, higher frequency of internet use in leisure time, and lower age of first internet use.
Conclusions: The present study provides new insights about the strengths and shortcomings of the IDS-15. Moreover, the results provide an insight into the prevalence of internet addiction in Slovenia, as well as associations with other potential factors. The results serve as the basis for further analyses on internet addiction epidemiology, policymaking activities, and design for targeted public health interventions in Slovenia.