Sex and intelligence quotient differences in age of diagnosis among youth with attention‐deficit hyperactivity disorder

Objectives Attention‐deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental condition and is characterized by inattention, hyperactivity, and impulsivity. Research suggests that some populations, such as females and individuals with high intelligence quotients may be a risk for late ADHD diagnosis and subsequent treatment. Our goal is to advance our understanding of ADHD diagnosis, by examining (1) how child sex and cognitive abilities together are related to the age of diagnosis and (2) whether symptom presentation, current internalizing and externalizing symptoms, and demographic factors are related to age of diagnosis. Methods Our analyses contained children who completed the required tests (N = 568) from a pre‐existing dataset of 1380 children with ADHD from the Province of Ontario Neurodevelopmental Disorders (POND) Network (pond‐network.ca). First, we conducted a moderation analysis with sex as the predictor, cognitive abilities as the moderator, and age of diagnosis as the outcome. Second, we conducted correlation analyses examining how symptom presentation, current internalizing and externalizing symptoms, and demographic factors are related to age of diagnosis. Results Higher IQ was related to a later age of diagnosis. Higher hyperactive–impulsive symptoms and externalizing symptoms were related to an earlier age of diagnosis. Internalizing symptoms were trend associated with a later age of diagnosis in girls. Higher socioeconomic status and non‐White maternal ethnicity were related to later age of diagnosis. Conclusions IQ, sex, ADHD symptomology, internalizing symptoms, externalizing symptoms, and socio‐demographic factors affect the age of diagnosis.