From traits to trajectories: How changes in reactive temperament relate to the development of externalizing symptoms

Temperament has been linked to the development of externalizing symptoms, but the nature of these associations remains unclear. Traditional approaches often treat early reactive temperament as static, overlooking developmental variation. This study applied a longitudinal latent change score model to examine how levels and changes in Negative Affect (NA) and Surgency from age 3 to 5 predict Conduct Problems (CP) and Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms in early childhood. Data from the National Educational Panel Study (<i>N</i> = 2,477) were analyzed. Temperament was assessed at ages 3, 4, and 5 using the Children's Behavior Questionnaire, and CP and ADHD symptoms were measured at ages 5, 6, and 8 with the Strengths and Difficulties Questionnaire. Measurement invariance was established. Significant individual differences in developmental change emerged. Change in NA and Surgency, but not baseline levels, predicted higher latent CP and ADHD symptom levels at age 5 and further increases through age 8. These findings indicate that intraindividual change in reactive temperament can be a relevant marker of developmental risk. Temperamental risk for externalizing symptoms in early childhood is not fixed but may be shaped by both stable dispositions and developmental change, highlighting the importance of assessing temperament development to identify early emerging risk.