International Classification of Diseases, used by the WHO (World Health Organisation), includes 10 groups such as delusional disorders, mood disorders, etc. and clinical/personality disorders are part of the same group
Different types of internet addiction were identified. This means it is not clear whether all types achieved the same effects of treatment (30% Males- pornography, 30% Females – online chat rooms)
Questionnaires about their own feelings and behaviour may be inaccurate because participants might lie or give socially desirable responses. This means data might not be a valid picture of how their behaviour has changed during treatment