A strength of this study was the use of a large, longitudinal dataset and the application of an advanced methodological approach that separates between-person (i.e., stable trait levels) and within-person (i.e., causal processes) associations, providing clear evidence for links between ADHD symptoms and both family and school climate independent from the DRD4 and 5-HTTLPR genotypes across adolescent development. Here, DRD4 is linked to attention deficit-hyperactivity disorder.