Antecedents and outcomes of a later attention deficit hyperactivity disorder (ADHD) diagnosis in females

Background: Females are less likely than males to be diagnosed with attention deficit hyperactivity disorder (ADHD). When diagnosed, females are older than males. Aims: In this study, we examined the childhood antecedents of later ADHD diagnosis and its impact on adolescent/emerging adult outcomes, with a focus on females. Method: In this cohort study, we used data from a Welsh nation-wide electronic cohort of 13,593 individuals (N=2,680 (19.7%) females) diagnosed with ADHD and 578,793 individuals (N=286,734 (49.5%) females) without ADHD. We compared females with later diagnoses (ages 12–25) to those with earlier, timely diagnoses (ages 5–11) and no diagnosis, in terms of childhood (ages 5–11) antecedents and adolescent/adult (ages 12–25) outcomes. We also tested for sex differences. Results: Although females with earlier ADHD diagnosis showed more health and educational difficulties in childhood than those with later diagnosed ADHD (ORs ranged from 0.18–0.92), there was clear evidence of these difficulties in females with later diagnosed ADHD, compared to females without ADHD (ORs: 1.07–9.02). In adolescence/early adulthood, females with later diagnosed ADHD used more healthcare services and had worse mental health, educational and socioeconomic outcomes than females diagnosed earlier (ORs: 1.39–4.96) and those without ADHD (ORs: 1.54–23.98). Many of these outcomes were exacerbated in females compared to males. Conclusions: The results demonstrate that later ADHD diagnosis is associated with significant negative outcomes by adolescence and disproportionately disadvantages females. Despite later diagnosis, there was clear evidence of childhood mental health and educational difficulties when compared to females without ADHD. Therefore, timely childhood ADHD diagnosis may help to mitigate later risks, especially for females.