Attention-deficit/hyperactivity disorder (ADHD) is heterogeneous in the age at which symptoms first lead to clinical diagnosis. Recent genomic analyses of a large Danish population-based cohort showed that individuals diagnosed in childhood differ from those diagnosed in adulthood in polygenic risk scores, rare-variant burden, and patterns of genetic correlation with other psychiatric traits [1]. Childhood cases exhibited stronger overlap with autism and higher rates of rare protein-truncating…
