Objective The objective of this study was to develop diagnostic criteria for internet addiction disorder (IAD) and to evaluate the validity of our proposed diagnostic criteria for discriminating non-dependent from dependent internet use in the general population.
Methods This study was conducted in three stages: the developmental stage (110 subjects in the survey group; 408 subjects in the training group), where items of the proposed diagnostic criteria were developed and tested; the validation stage (n = 405), where the proposed criteria were evaluated for criterion-related validity; and the clinical stage (n = 150), where the criteria and the global clinical impression of IAD were evaluated by more than one psychiatrist to determine inter-rater reliability.
Results The proposed internet addiction diagnostic criteria consisted of symptom criterion (seven clinical symptoms of IAD), clinically significant impairment criterion (functional and psychosocial impairments), course criterion (duration of addiction lasting at least 3 months, with at least 6 hours of non-essential internet usage per day) and exclusion criterion (exclusion of dependency attributed to psychotic disorders). A diagnostic score of 2 + 1, where the first two symptoms (preoccupation and withdrawal symptoms) and at least one of the five other symptoms (tolerance, lack of control, continued excessive use despite knowledge of negative effects/affects, loss of interests excluding internet, and use of the internet to escape or relieve a dysphoric mood) was established. Inter-rater reliability was 98%.
Conclusion Our findings suggest that the proposed diagnostic criteria may be useful for the standardization of diagnostic criteria for IAD.