Association between Smoking and Problematic Internet Use among Japanese Adolescents: Large-Scale Nationwide Epidemiological Study

The aim of this study was to clarify the association between smoking and problematic Internet use (PIU), such as Internet addiction (IA) and excessive Internet use (EIU), among Japanese adolescents. A self-administered questionnaire was administered to students enrolled in randomly selected junior and senior high schools throughout Japan. Responses were obtained from 100,050 students (0.94:1 ratio of boys to girls). The prevalence of IA (as indicated by a Young Diagnostic Questionnaire for Internet Addiction score ≥5) in all participants, boys, and girls was 8.1%, 6.4%, and 9.9%, respectively. The prevalence of EIU (≥5 hours/day) in all participants, boys, and girls was 12.6%, 12.3%, and 13.0%, respectively. The results of multiple logistic regression analyses indicated that the adjusted odds ratios (AORs) for IA and EIU were significantly higher among students who smoked (including those who previously smoked) than among those who never smoked (p < 0.01 for all comparisons). In addition, the AORs were the highest for students who smoked ≥21 cigarettes per day. The prevalence and AORs of IA and EIU tended to increase with smoking frequency and number of cigarettes smoked per day, indicating a dose-dependent relationship. Thus, IA and EIU have strong associations with smoking. This study revealed that adolescents who routinely smoked or those who smoked more cigarettes per day had a higher risk of PIU than adolescents who did not. These findings suggest that there is a close association between smoking and PIU among Japanese adolescents.