OBJECTIVE—To determine the clinical and psychological course of diabetes through adolescence and the relationship with glycemic control in young adulthood. RESEARCH DESIGN AND METHODS—A longitudinal cohort study of adolescents recruited from the register of the outpatient pediatric diabetes clinic. A total of 76 individuals (43 male patients, 33 female patients) aged 11–18 years completed baseline assessments, and 65 individuals (86%) were reinterviewed as young adults (20–28 years of age). Longitudinal assessments were made of glycemic control (HbA1c), weight gain (BMI), and development of complications. Adolescents completed self-report questionnaires to assess emotional and behavioral problems as well as self-esteem. As young adults, psychological state was assessed by the Revised Clinical Interview Schedule and the self-report Brief Symptom Inventory. RESULTS—Mean HbA1c levels peaked in late adolescence and were worse in female participants (average 11.1% at 18–19 years of age). The proportion of individuals who were overweight (BMI >25.0 kg/m2) increased during the 8-year period from 21 to 54% in female patients and from 2 to 28% in male patients. Serious diabetes-related events included death in one patient and cognitive impairment in two patients. Individuals in whom diabetic complications developed (25% of male patients and 38% of female patients) had significantly higher mean HbA1c levels than those without complications (difference 1.9%, 95% CI 1.1–2.7, P < 0.0001). Behavioral problems at baseline were related to higher mean HbA1c during the subsequent 8 years (ß = 0.15, SEM (ß) 0.04, P < 0.001, 95% CI 0.07–0.24). CONCLUSIONS—The outcome for this cohort was generally poor. Behavioral problems in adolescence seem to be important in influencing later glycemic control. <br/
