Autism spectrum disorder (ASD) is a common, chronic neurodevelopmental disorder with a multifactorial etiology. It is characterized by a high degree of heterogeneity in clinical presentations and course. Factors related to its severity are poorly understood, largely due to the scarcity of multidimensional databases containing rigorously documented cases. Between 2013 and 2019, the Elena cohort recruited 900 children with a formal diagnosis of ASD, who will be followed for six years, with the study concluding in 2025. The primary objective is to study the developmental trajectories of these children and to explore their determinants through a comprehensive collection of data on clinical, psychological, social, biological, and environmental variables. This article describes the methodology, preliminary results, future directions, and expected outcomes of our project.