IntroductionJapan is assumed to have serious health and social problems due to Internet overuse, but little is known about the actual conditions. This study was conducted to investigate the prevalence of problematic Internet use (PIU) and associated Internet use in adolescents in Japan.MethodsA nationwide survey of adolescent Internet use was conducted in 2012 and 2013. The participants were 100,050 students from randomly selected junior and senior high schools nationwide who gave valid responses to a self-reported questionnaire. The questionnaire included questions on Internet use and the Japanese version of the Young's Diagnostic Questionnaire (YDQ) as well as other questions related to lifestyle habits. Internet users were classified by gender according to three categories on the basis of their YDQ scores: adaptive use, maladaptive use, and PIU.ResultsThe estimated prevalence of PIU was 6.2% in males, 9.8% in females, and 7.9% in total; it closely correlated with female gender, school grades, and number of Internet hours. The following common and gender-specific applications that conferred a risk of PIU were identified: downloading (both genders), online gaming (males), social networking services, blogs, and bulletin boards (females).ConclusionsA cross-sectional survey using YDQ of a large number of high school students yielded a PIU prevalence of 7.9% in Japan. This study showed that problems associated with Internet overuse have already become serious; therefore, planning and implementation of prevention and control measures is urgently required.

Recently, many young people have developed Internet use disorders (IUD) as a result of the proliferation of Internet-enabled devices, leading to serious health and social problems worldwide. On occasion, medical and educational institutions, governments, and other groups have sought to take preventive action or treat IUD. In many cases, the preferred treatment for IUD is to set recommendations for appropriate Internet use. Reportedly, psychosocial therapies (including cognitive behavioral therapy, family therapy, and compound therapy) for IUD and pharmacotherapies (including antidepressant drugs and psychostimulants) for comorbid psychiatric or development disorders have been effective at reducing the degree and symptoms of IUD. In some countries, treatment camps have been developed for adolescents with IUD, and preventive education (including lectures and group discussions) has been provided for general adolescents. Such efforts have been effective at reducing the average degree of IUD severity. Some future IUD risk factors (e.g. being male, suffering from attention-deficit hyperactivity disorder, and exhibiting deteriorating psychiatric symptoms) have begun to be identified. However, clinical studies, treatment, and preventive actions are insufficient for treating IUD and standard treatments and preventive systems have yet to be established. Educational and medical institutions, government, families, and others must take greater action and cooperate more effectively in order to treat or prevent IUD.

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Data from a specialist treatment facility for Internet addiction (IA) in Japan showed that (a) the vast majority of treatment seekers are addicted to online games, (b) their symptoms are often quite severe, and (c) there is a significant demand for IA treatment. In addition, systemic obstacles to the delivery of medical services in Japan exist due to the exclusion of IA criteria from ICD-10. Consequently, the inclusion of GD criteria in ICD-11 will almost certainly increase the capacity and quality of treatment through advances in research and possible changes in national medical systems to meet treatment demand.

Background and aims An important proportion of infants and adolescents in Japan are using Internet-equipped devices, including smartphones, tablets, and game consoles. However, the relationship between the risk of IA and the age at initial habitual Internet use remains unknown. We aimed to investigate this relationship among adolescents. Methods We surveyed 1,775 subjects in seven public junior high schools in Kanagawa prefecture, Japan, in November 2017. Students were asked to complete the Young's Diagnostic Questionnaire (YDQ), which captured information regarding gender, school grade, night sleep, age at which they first started using the Internet at least once weekly, Internet usage situation, and Internet use time for purposes other than study. Data from subjects who reported experience of weekly Internet use were analyzed. Results Junior high school students who were younger at initial weekly Internet use tended to have problematic Internet use (PIU) and to spend more time on Internet activities. In particular, initial weekly Internet use before the age of five in boys was associated with a significantly increased risk of PIU (YDQ ≥ 5), with an odds ratio of 14.955, compared with initial weekly Internet use after the age of 12. Smartphone ownership significantly increased the risk of PIU compared with no ownership among the total population and among girls. Discussion and Conclusions Junior high school male students displayed a robust relationship between initial weekly Internet use and PIU, whereas junior high school female students displayed a particularly strong relationship between smartphone ownership and PIU. Therefore, longitudinal IA preventive education from an early age is necessary.