Background: Premature infants may be at risk for lower effortful control, and subsequent lower academic achievement, peer competence, and emotional and physical wellness throughout the lifespan. However, because prematurity is related to obstetrical and neonatal complications, it is unclear what may drive the effect. Effortful control also has a strong heritable component; therefore, environmental factors during pregnancy and the neonatal period may interact with genetic factors to predict effortful control development. In this study, I aimed to dissect the influences of genetics, prematurity, and neonatal and obstetrical complications on the development of effortful control from 12 months to 10 years using a twin cohort. Methods: This study used data from the Arizona Twin Project, an ongoing longitudinal study of approximately 350 pairs of twins. Twins were primarily Hispanic/Latinx (23.8%-27.1%) and non-Hispanic/Latinx White (53.2%-57.8%), and families ranged in socioeconomic status with around one-third falling below or near the poverty line. Of the twins, 62.6% were born prematurely. Effortful control was assessed via parent report at six waves. Results: There was not a significant relationship between gestational age and effortful control regardless of whether obstetrical and neonatal complications were controlled for. Biometric twin modeling revealed that the attentional focusing subdomain of effortful control was highly heritable. Gestational age did not moderate genetic and environmental estimates. Conclusions: The findings help inform the risk assessment of prematurity and provide evidence for differing etiology of each subdomain of effortful control and the strong role of genetics in effortful control development.

Among children in the United States, there is a high prevalence of psychopathology. Understanding what contributes to the development of these disorders in early adolescence and late childhood is key to informing intervention efforts. This study aimed to understand the impacts of economic and social stress on the development of internalizing and externalizing psychopathology in children. Additionally, with the knowledge that supportive adult relationships can buffer psychopathology impacts, it sought to uncover if supportive sibling relationships can alter the relationship between stress and psychopathology. Data was collected through both home visits and online questionnaires as part of the Arizona Twin Project. The sample of the twins at eight years old included 355 families (M = 8.43 years, SD = .68) and 709 twins (MZ = 29.9%, same-sex DZ = 37.8%, opposite-sex DZ = 31.7%, and unknown zygosity = 0.6%) with ethnically and socioeconomically diverse backgrounds. Families were followed longitudinally with annual assessments at ages 9, 10, and 11. Our results showcased a significant positive relationship between economic stress and the development of internalizing and externalizing psychopathology symptoms in children. Our social stress indicators were categorized into family stress and negative parenting constructs. It was observed that family stress was linked to an increase in both internalizing and externalizing symptoms. However, when it came to parenting behaviors, no significant associations were identified with the development of either externalizing or internalizing symptoms in our study. In terms of the potential moderating effects of a positive sibling relationship, no significant results were found. Ultimately, our study showcases the adverse impact of stress on children and early adolescents. Further research on the impacts of the relationship between siblings can help us to better understand the dynamics in the home as a whole and explore whether relationships beyond those with supportive adults can contribute to resilience in children. This knowledge may guide interventions and preventive measures aimed at mitigating the effects of psychopathology in young individuals.