Illness Identity in Type 1 Diabetes: A Nine-Year Longitudinal Perspective in Belgian Youth

This study offers a unique long-term perspective on the development of illness identity in young individuals with type 1 diabetes and examines how this process relates to their psychological and diabetes management outcomes over time. From a seven-wave longitudinal study, spanning 9 years, data was used from 403 Dutch-speaking adolescents and emerging adults with type 1 diabetes (ages 14-25 years at baseline). The group-level development of illness identity was examined using multivariate latent growth curve modeling, and distinct developmental trajectory classes of illness identity were identified through multivariate latent class growth analysis. Mean differences in depressive symptoms, self-reported management, and hemoglobin A1c across these classes were evaluated using the Bolck-Croon-Hagenaars method. At the group level, small but significant changes were observed with youth reporting more acceptance, enrichment, and engulfment, and less rejection over time. Next, five distinct trajectory classes were identified, each displaying unique developmental patterns of the illness identity dimensions. Youth in these classes differed substantially in their experience of depressive symptoms, self-reported management, and hemoglobin A1c over time. This study demonstrates the heterogeneity in how young individuals with T1D develop their illness identity and how these differences are tied to meaningful variation in psychological and diabetes-related functioning. These findings support illness identity as a clinically relevant target to inform holistic, person-centered care for individuals with type 1 diabetes.