Trajectories of childhood atopic dermatitis and their association with attention‐deficit hyperactivity disorder

Background The comorbidity between atopic dermatitis (AD) and attention‐deficit hyperactivity disorder (ADHD) has garnered attention, yet their longitudinal relationship remains unclear. Understanding how AD trajectories relate to ADHD risk is crucial for elucidating the mechanisms underlying this comorbidity. Methods This single‐center, retrospective cohort study included 1992 AD patients born between 2013 and 2014. Data on AD frequency during the first decade of life (10 timepoints), ADHD outcomes (diagnosis or reported symptoms), and various risk‐factor covariates were collected from electronic medical records and telephone follow‐ups. Group‐based trajectory modeling was used to assess AD trajectories; ADHD odds across AD trajectories were analyzed using Firth's penalized likelihood logistic regression. Results A series of two‐ to five‐cluster models for AD trajectories was analyzed, ultimately identifying a four‐cluster solution (entropy = 0.96): early‐onset transient (EOT), early‐onset persistent (EOP), mid‐onset transient (MOT), and late‐onset persistent (LOP). ADHD diagnoses and symptoms were identified in 215 (10.8%) and 243 (12.2%) participants, respectively. Regression analysis identified that the EOP and EOT groups had 3.7 (OR = 3.7, 95% CI: 2.1–7.1, p < .001) and 2.7 (OR = 2.7, 95% CI: 1.5–5.3, p < .001) times higher odds of an ADHD diagnosis, as well as 3.0 (OR = 3.0, 95% CI: 1.8–5.3, p < .001) and 2.1 (OR = 2.1, 95% CI: 1.3–3.7, p = .004) times higher odds of reported ADHD symptoms, respectively, compared with the LOP group. Conclusions Childhood AD trajectories characterized by early‐life AD exposure were associated with higher odds of ADHD, with persistent exposure potentially exerting a cumulative effect. These findings provide insights into the underlying pathogenesis linking AD and ADHD and may inform future intervention strategies.