Objective: This study examined trajectories of inattention and hyperactivity/impulsivity symptom levels across one preschool year and explored variation in trajectories by age, sex, and end-of-year impairment.
Method: Participants were 261 preschoolers (87% Head Start; 59% Caucasian; 53% boys; Mage = 3.97 years). Teachers rated ADHD symptom levels four times throughout one academic year.
Results: Results showed a course of increasing inattention that decelerated over time and steadily increasing hyperactivity/impulsivity. Group-based finite mixture modeling revealed three trajectories of inattention: stable low (57%), change (32%), and stable high (11%), as well as three trajectories of hyperactivity/impulsivity: stable low (63%), increasing (26%), and stable high (11%). Compared to children with increasing or changing symptoms levels, children with stable high levels were more impaired and children with stable low symptom levels were less impaired.
Conclusion: Findings suggest a "wait and see" approach to treatment may miss an important opportunity for early intervention.
Keywords: attention-deficit/hyperactivity disorder; developmental trajectories; early childhood; finite mixture models; impairment; preschool.