Early-life factors associated with developmental trajectories of internalizing and externalizing symptoms from early childhood through adolescence: Rhea mother—child cohort in Crete, Greece

PURPOSE: The developmental trajectories of internalizing and externalizing symptoms, including ADHD, vary widely among individuals, yet the factors that contribute to these diverse patterns are not fully understood. Our specific objectives are to empirically identify developmental trajectories of internalizing, externalizing, and ADHD symptoms from ages 4 to 15, and to explore how early-life risk factors are linked to these trajectory groups. METHODS: The study included 551 mother-child pairs of the Rhea mother-child cohort in Crete, Greece. Children's internalizing, externalizing, and ADHD symptoms were evaluated using maternal reports at ages 4 (Strengths and Difficulties Questionnaire, ADHD Test), 6, 11 and 15 years (Child Behavior Checklist, Conners' Parent Rating Scale-Revised). Group-based trajectory modeling was applied to identify trajectory groups from 4 to 15 years and multinomial logistic regression models were implemented to examine the associations between early-life risk factors and group trajectories. RESULTS: The analysis revealed four distinct trajectories for each outcome (internalizing, externalizing, and ADHD symptoms): stable low, high-decreasing, low-increasing, and stable high symptoms. Furthermore, several early-life sociodemographic and perinatal factors, such as sex, maternal and paternal age, paternal education, maternal smoking during pregnancy, and breastfeeding duration were significantly linked to the development of internalizing, externalizing, and ADHD symptoms. CONCLUSION: The study highlights the complex and dynamic nature of emotional and behavioral symptom development and the critical role of early-life determinants in shaping these trajectories. Findings suggest that early identification and intervention are crucial for preventing the persistence of psychopathology into adolescence.