Background Addicted Internet users present with higher rates of comorbidities, e.g., attention-deficit hyperactivity disorder (ADHD), depressive, and anxiety disorders. In addition, deficits in self-concept-related characteristics were found in addicted Internet gamers and social network users. The aim of this study was to examine the links between healthy, problematic, and addicted Internet use regarding comorbidities and self-concept-related characteristics. The association between recently developed ADHD-like symptoms without an underlying diagnosis and addictive Internet use was also examined. Methods n = 79 healthy controls, n = 35 problematic, and n = 93 addicted Internet users were assessed for comorbidities, social and emotional competencies, body image, self-esteem, and perceived stress. Apart from an ADHD-diagnosis, recently developed ADHD-like symptoms were also assessed. Results Addicted users showed more self-concept-related deficits and higher rates of comorbidities with ADHD, depressive, and anxiety disorders. Addicted and problematic users showed similarities in the prevalence of cluster B personality disorders and decreased levels of characteristics related to emotional intelligence. Participants with recently developed ADHD-like symptoms scored higher in lifetime and current severity of Internet use compared with those without ADHD symptoms. Addicted participants with recently developed ADHD symptoms showed higher lifetime Internet use severity compared with those without any symptoms. Conclusions Our findings indicate that cluster B personality disorders and premorbid problems in emotional intelligence might present a link between problematic and addictive Internet use. Furthermore, the findings provide a first indication that addictive Internet use is related to ADHD-like symptoms. Symptoms of ADHD should therefore be assessed against the background of possible addicted Internet use.
Keywords: ADHD symptoms; comorbidities; problematic and addicted Internet use; self-concept.