Background and aims: Social variables including parental and family factors may serve as risk factors for Internet Gaming Disorder (IGD) in adolescents. An IGD treatment programme should address these factors. We assessed two family therapies - multidimensional family therapy (MDFT) and family therapy as usual (FTAU) - on their impact on the prevalence of IGD and IGD symptoms. Methods: Eligible for this randomised controlled trial comparing MDFT (N 5 12) with FTAU (N 5 30) were adolescents of 12-19 years old meeting at least 5 of the 9 DSM-5 IGD criteria and with at least one parent willing to participate in the study. The youths were recruited from the Centre Ph
enix-Mail, which offers outpatient adolescent addiction care in Geneva. Assessments occurred at baseline and 6 and 12 months. Results: Both family therapies decreased the prevalence of IGD across the one-year period. Both therapies also lowered the number of IGD criteria met, with MDFT outperforming FTAU. There was no effect on the amount of time spent on gaming. At baseline, parents judged their child?s gaming problems to be important whereas the adolescents thought these problems were minimal. This discrepancy in judgment diminished across the study period as parents became milder in rating problem severity. MDFT better retained families in treatment than FTAU. Discussion and Conclusions: Family therapy, especially MDFT, was effective in treating adolescent IGD. Improvements in family relationships may contribute to the treatment success. Our findings are promising but need to be replicated in larger study. Trial registration number: ISRCTN 11142726.  Kulcsszavak: internet gaming disorder, adolescent, multidimensional family therapy, randomised controlled tria