Baseline Psychopathology and Developmental Trajectories of ADHD Symptoms from Late Childhood Through Adolescence

Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms show substantial developmental heterogeneity, yet less is known about how co-occurring psychopathology is associated with membership in different longitudinal symptom trajectories. This study examined developmental trajectories of parent-reported ADHD symptoms across seven annual assessment waves from late childhood through adolescence using data from the Adolescent Brain Cognitive Development (ABCD) Study. ADHD symptoms were assessed using the Child Behavior Checklist DSM-5-Oriented ADHD Problems scale and therefore represent dimensional symptom scores rather than clinical ADHD diagnoses. Growth mixture modelling was conducted in an analytic sample of 9718 participants and identified three trajectory classes: low/stable (79.87%), high/stable (10.77%), and remitting (9.36%). Baseline associations with class membership were subsequently examined using the R3STEP procedure in 9716 participants, preserving the identified class structure while accounting for classification uncertainty. Relative to the low/stable class, male sex and higher baseline affective, anxiety, conduct, and oppositional defiant problem scores were associated with greater odds of membership in both the remitting and high/stable classes, whereas age and somatic problems showed no clear associations. Comparisons between the remitting and high/stable classes were largely similar, although male sex was associated with greater odds of remitting-class membership. Overall, the findings demonstrate substantial heterogeneity in the developmental course of ADHD symptoms and suggest that baseline co-occurring psychopathology is associated primarily with differentiation between lower- and higher-symptom trajectories rather than clearly distinguishing persistent from remitting elevated-symptom pathways.