This study was done for the TEENCOPE Study Group.

Objective To determine mediators of 12-month outcomes of Internet interventions for youth with type 1 diabetes transitioning to adolescence. Methods In this multisite clinical trial, 320 youth were randomized to one of two Internet-based interventions: Coping skills (TEENCOPETM) or diabetes education (Managing Diabetes). Mediators of the interventions ’ effects on glycosylated hemoglobin and quality of life were exam-ined. Data were collected at baseline and at 3, 6, and 12 months. Results Self-efficacy mediated treat-ment effects on quality of life in both interventions. For TEENCOPETM, stress reactivity, primary control coping, and secondary control coping mediated treatment effects, whereas for Managing Diabetes, social ac-ceptance mediated treatment effects. There were no significant effects of either intervention on glycosylated hemoglobin. Conclusions 2 Internet interventions for youth with type 1 diabetes resulted in improved quality of life by different mechanisms, suggesting components of both diabetes education and coping skills may help to achieve better outcomes in youth with type 1 diabetes. Key words coping skills; intervention studies; quality of life; type 1 diabetes mellitus. Type 1 diabetes is one of the most common and challeng-ing chronic illnesses affecting youth in the United States, with projected estimates of the incidence increasin