Purpose: This study investigated the prevalence and correlates of problematic internet use (PIU) in a large sample of adolescents based on the type of internet service used. Materials and Methods: The study was conducted from 2008 to 2010, and 223,542 adolescents aged 12 to 18 years participated in the study. The participants responded to a self-report questionnaire including items for demographic factors, internet usage time, most used internet service and mental health. The PIU was assessed with the Internet Addiction Proneness Scale for Youth-Short Form. Results: The overall prevalence rate of PIU was 5.2%, and the prevalence rates stratified by sex were 7.7% in boys and 3.8% in girls. The distribution of most used internet services was significantly different across sexes. The most commonly used internet services were gaming (58.1%) in boys and blogging (22.1%) and messenger/chatting (20.3%) in girls. The odds ratio for PIU was significantly different according to the most used internet service; using the internet mostly for pornography compared to information searching had the highest odds ratio (4.526-fold higher). Depressive episodes, suicidal ideation, and suicidal attempts were significantly associated with higher odds ratios for PIU (1.725-, 1.747-and 1.361-fold, respectively). Conclusion: The present study identified clinically important information about PIU in adolescents. The distribution of PIU has different patterns based on sex and specific internet services. Studies of PIU with well-defined methodology and assessment tools for PIU of each specific internet service are needed.

In a case of 46-year-old woman suffering from schizophrenia for over 20 years, she experienced frequent episodes of dyspnea and confirmed as superimposed with myasthenia gravis (MG). Throughout the seven-year follow-up period, after diagnosed as MG, she has been hospitalized 6 times and also diagnosed as colorectal cancer. Authors experienced various conditions associated with untoward effects of medication for myasthenia, schizophrenia, and colorectal cancer. Therefore, authors reported considerations for the pharmacotherapy of schizophrenia with myasthenia gravis.