In the scientific report (Handygebrauch der Schweizer Jugend; April 2012) Gregor Waller and Daniel Süss of the University of Applied Sciences Zurich report a handy (that is the Swiss word for mobile phone) dependence of 5.3% in a representative sample with 1223 Swiss youths (age 12 to 19). The predictors found for mobile phone dependence are negative relationship to parents, extraversion (activity) and impulsivity (urgency).
In my opinion, these predictors are hints that youths with a mobile phone dependence have some further problems in their life. Often persons with one problem behaviour show also other problematic behaviours and / or disorders (e.g. review of Amstrong et al., 2002 about youth substance dependence and psychiatric comorbidity: DOI: 10.1037/0022-006X.70.6.1224).
I suppose, most of these 5% with a mobile phone dependence are youths that accumulate some other problems like absenteeism, substance use, internal and external problems? Reviews report up to 50% and more comorbidity of internal, external and substance use disorders (e.g. Cowenbergh et al., 2006; DOI: 10.1007/s00787-006-0535-6).
The main problem would not be mobile phone dependence. But: these young people are just the “bad and unlucky ones”.