From the abstract: "Objective: Recent studies suggest attention-deficit/hyperactivity disorder (ADHD) may emerge post-childhood. We integrate qualitative methods to systematically characterize contextual factors that may (a) delay identification of ADHD in childhood and (b) inform why ADHD symptoms emerge post-childhood. Method: Suspected late-onset ADHD cases from the local normative comparison group of the Multimodal Treatment Study of ADHD completed a qualitative interview (14 young adults and 7 caregivers). Interviews were qualitatively analyzed. Results: We identified five themes. Three themes may attenuate or delay identification of childhood ADHD: external factors (e.g., supportive adults), internal factors (e.g., strong intellectual functioning), and other factors (e.g., dismissive attitudes toward ADHD). Two themes may accompany an increase in ADHD symptoms post-childhood: external factors (e.g., increased external demands) and internal factors (e.g., perceived stress). Conclusion: Clinicians should probe these factors in suspected late-onset cases to address (a) whether, how, and to what extent ADHD was attenuated in childhood and (b) why symptoms emerge post-childhood."