Throughout childhood, self-control undergoes substantial development, influenced by both genetic and environmental factors. Although the relative ranking of individuals’ self-control levels stabilizes in early adolescence, the developmental trajectory of the genetic risk for low self-control (LSC) remains poorly understood. This gap in our knowledge raises some critical questions: Is the genetic risk for LSC the same across childhood or are there specific developmental windows during which the risk exerts its strongest influence? Importantly, how do environmental factors, such as parenting, socioeconomic status, or neighbourhood characteristics, modify this genetic risk? This project aims to provide the first comprehensive answers to these questions. Focusing on childhood is crucial as this life stage is strongly shaped by environmental factors, making it an ideal target for intervention strategies, and these analyses will help to identify the optimal timeframe for maximizing the effectiveness. To achieve this objective, longitudinal structural equation modelling (SEM) will examine the dynamic association between LSC polygenic score (PGS) and early phenotypic manifestations in cohorts from 3 countries (UK, NL, CZ) and identify critical developmental windows. The models will incorporate selected environmental factors to test for gene-environment interaction (GxE).