DDepression affects up to 300 million people worldwide and is one of the greatest causes of disability in the world. While many aspects of depression trajectories from adolescence to adulthood are well understood, depression is still among the most unreliable diagnoses of all categorical mental disorders. Additionally, changes in symptom levels across adolescence and young adulthood are as yet poorly understood. This may result from nosological conceptualizations of mental disorders that do not vary for children as compared to adolescents or adults. Only the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders describes irritability rather than depressed mood as an additional core symptom for children and adolescents. In this vein, researchers and practitioners often apply sum score models that reflect these considerations. However, these models rely on strong assumptions and we therefore aim to use Avon Longitudinal Study of Parents and Children data to investigate depressive symptoms in more depth.