Late-Onset ADHD symptoms in the general population: A scoping review of longitudinal trajectories in population-based cohorts

Background and objectives The developmental validity of late-onset ADHD remains debated. This scoping review aimed to synthesize evidence from longitudinal trajectory studies in the general population to (1) examine the existence and characteristics of late-onset ADHD symptom trajectories, and (2) identify associated factors. Methods Following PRISMA-ScR guidelines, we systematically reviewed longitudinal studies published up to May 2025 that applied person-centered trajectory modeling to ADHD symptoms in population-based cohorts. Twelve eligible studies were included. Results Among the twelve studies included in this scoping review, ten identified at least one symptom trajectory consistent with late-onset ADHD, with prevalence estimates ranging from 3 % to 17.5 %, and were analyzed to examine associated factors. These late-onset trajectories were predominantly inattentive and less disruptive than persistent profiles, but consistently observed across cohorts but were reported in the majority of cohorts (10/12), not all. The most robustly supported associated factors included higher childhood cognitive functioning, fewer early externalizing problems, emerging internalizing psychopathology during adolescence, lower family socioeconomic status, female gender, and polygenic liability for ADHD. However, methodological variability, particularly in informant source, symptom measurement and model specification, significantly influenced identification. Notably, no study assessed sleep-wake disturbances, treatment history, contextual supports or neurological antecedents. Conclusion Late-onset ADHD trajectories are commonly identified in general population cohorts (10/12 studies). Their interpretation calls for a dimensional, developmentally sensitive framework. Future studies should incorporate overlooked domains such as sleep-wake functioning, treatment exposure, and neurological risk factors to refine clinical characterization and diagnostic criteria.