Background: Internet environments have made everyday life more convenient. On the other hand, an increasing number of people face problems in their daily lives due to excessive Internet use. Especially, Internet overuse among adolescents and young adults is of particular concern. When junior high schools were closed during the COVID-19 pandemic in 2020, it was feared that Internet dependence tendency of junior high school students would grow.

Objective: To clarify the association between Internet dependence tendency of junior high school students and problematic behaviors/physical symptoms related to Internet use during school closures under the emergency declaration, and to identify factors promoting and suppressing the tendency.

Methods: A self-administered questionnaire survey was conducted, involving 1,532 students aged 12 to 14, who had belonged to 4 junior high schools in an urban area during the period from June to July 2020. Among these students, 1,001 (male: 498; female: 503; 65.3%) without missing data for any item were analyzed.

Results: The prevalence of spending more than 2 hours for each type of Internet content was as follows: video and information search 50.5%, social networking service 25.7%, and online games 33.6%. The prevalence of Internet dependence was 11.7%, and those with Internet dependence showed more problematic behaviors and physical symptoms resulting from Internet use. The school year, time spent online, school maladjustment, need for approval, depression, and self-management skills were also found to be related to the presence of Internet dependence.

Conclusion: The results of this study showed that there was a relationship between Internet dependence tendency of junior high school students and problematic behaviors and physical symptoms resulting from Internet use when school was closed under a state of emergency, and that the factors that promoted Internet dependence tendency of junior high school students were school year, time spent online, feeling of school maladjustment, need for approval, and depression. The factors that inhibited the tendency to Internet dependence were self-management skills.