Although there is extensive research on temperament and its relation to psychopathology, most studies to date have used a dimensional approach to temperament, assessing one or two temperament traits at a time, which does not account for the interrelatedness between temperament dimensions. Recent studies have identified statistical methods that can capture these heterogenous relations that take a more typological approach. The current study used data from a racially/ethnically and socioeconomically diverse sample of twins to investigate whether using these different analytic methods together to capture temperament contribute to the conceptualization of phenotypic and genetic temperamental risk for later cross-reporter factors of anxiety, depression, externalizing, and ADHD. In breaking psychopathology down into its respective components, as measured by multiple reporters, I found that temperamental genetic risk for psychopathology differed depending on the psychopathology factors assessed. In using both dimensional and typological approaches to temperament, I found that high negative emotionality may only act as a risk factor for anxiety and ADHD when children also have low effortful control and high impulsivity. Results also showed an inconsistent role of genetics and the environment that explain the relation between temperament and psychopathology depending on the approach used. Examining typological and dimensional approaches together supported well-known findings and challenged others, highlighting importance of taking multiple approaches in investigating the phenotypic relation between temperament and psychopathology, and its etiology.

Aggressive and violent behavior is expressed differently across development, but for some adolescents, this behavior leads to criminal justice involvement through arrests and incarceration. Further, according to the biopsychosocial model, aggressive behavior is influenced by both genetics and the environment. This study sought to examine the differential impacts of early childhood environmental cumulative risk and genetic risk on the developmental cascade from middle childhood behavioral aggression and lack of control to adolescent antisocial behavior or callous-unemotional traits, to emerging adult involvement with the criminal justice system, and whether the effects of risk were mitigated by receiving the Family Check-Up (FCU) prevention program in childhood. The sample included high-risk youth (N = 731; 50% female, 50% White, 28% Black, 13% Hispanic, 9% Indigenous, Native Hawaiian, or Asian; of these 13% were multiracial; Mincome = $28,993; representative 515 genotyped) involved in a randomized-controlled trial of the Family Check-Up and followed longitudinally across 11 waves from ages 2 through 19 years. Behavioral measures included parent-report of behavioral aggression and observational lack of control in middle childhood, self-report of antisocial behavior and callous-unemotional (CU) traits in adolescence, and self-report of involvement with the legal system at age 19. Results of longitudinal structural equation modeling (SEM) supported a developmental cascade from middle childhood behavioral aggression to antisocial behavior in adolescence to legal system involvement. Early cumulative environmental risk and polygenic risk tolerance (RT PGS) significantly predicted involvement with the legal system at age 19, while RT PGS also predicted antisocial behavior in adolescence. Further, intervention effects were found for the FCU, such that the FCU disrupted the effects of RT PGS and middle childhood aggression on antisocial behavior and CU traits in adolescence. This study showed that the FCU can mitigate polygenic risk, supporting the benefit of early psychosocial prevention programs. Importantly, this study showed initial evidence that prevention programs targeting early childhood conduct problems could potentially reduce rates of justice system involvement, including arrests and incarceration, by the age of 19.

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.

This dissertation combines three first-author manuscripts that focused broadly on the study of adolescent sleep within a family context (Sasser et al., 2021; Sasser & Oshri, 2023; Sasser et al., 2023). First, Chapter 1 introduces the theoretical background and empirical research that grounded the research questions and hypotheses explored across the studies. The first study (Chapter 2) examined the influence of family connection on actigraphy-measured sleep among Latinx late adolescents and explored family dynamics and cultural values as potential moderators. The second study (Chapter 3) investigated daily and average concordance between parent and youth actigraphy-measured sleep and how this varied as a function of family context (e.g., parenting, family functioning). The third study (Chapter 4) examined concordance in actigraphy sleep among parent-youth and sibling dyads and explored how relations differed across zygosity type and sleeping arrangements. The dissertation concludes with an immersive discussion (Chapter 5) that summarizes the key differences, similarities, and takeaways across studies and highlights future directions and implications for developmental science, public policy, and clinical interventions. Collectively, this dissertation contributes to the understanding of youth and adolescent sleep within a family context by identifying proximal (e.g., daily interactions with parents/siblings) and broader family-level factors (e.g., dynamics, culture) that may help promote more healthful sleep among both adolescents and their family members.

Various physical and psychological forms of development take place during the transition from childhood to adolescence, including the onset of puberty, delayed sleep-wake behavior patterns, and increases in internalizing symptomatology. Theory suggests that pubertal processes influence the onset of internalizing symptoms, and this association may differ between boys and girls. The contextual amplification hypothesis suggests that pubertal development interacts with contextual or dispositional factors to impact risk for psychopathology. Family stress and peer stress are two critical factors during early adolescence that have potential moderating effects on the association between pubertal development and internalizing symptoms. In line with the biopsychosocial framework, the current study examined various psychosocial (e.g., family stress, peer stress) and biological (e.g., sleep, genetics) factors that may have effects on the puberty-internalizing relation. Participants were a racially/ethnically and socioeconomically diverse sample of twins who were part of an ongoing longitudinal study (N=818 children; Arizona Twin Project; Lemery-Chalfant et al. 2019). The current study examined the association between puberty and internalizing symptoms, with stress (i.e., family, peer) as potential moderators, and sleep indicators (i.e., objective and self-reported sleep) as potential mediators. Behavior genetic analyses explored the moderated heritability of family stress on internalizing symptoms. Findings revealed that greater pubertal development predicted higher internalizing symptoms in boys, but not girls. For girls, peer stress interacted with pubertal development to predict internalizing symptoms, but simple slopes were not significant. Sleep indicators were not significant mediators between pubertal development and internalizing symptoms for boys or girls. Univariate twin models revealed environmental influences on internalizing symptoms, and both genetic and environmental influences on peer stress. Family stress did not significantly moderate the genetic and environmental influences of internalizing symptoms.

Approximately 20% of youth experience mental health problems (Vasileva et al., 2021), and dimensions of early childhood temperament, specifically negative affectivity and effortful control, predict later mental health (Rothbart, 2007). Examining temperament using person-centered methods, particularly in stressful contexts, may improve our understanding of vulnerability to adolescent emotional problems. The current study examined whether specific patterns, or types, of infant temperament longitudinally predicted adolescent anxiety and depression symptoms and whether family relationship stress moderated this association. We hypothesized that infants with a Negative Dysregulated temperament would experience higher anxiety and depression symptoms in later childhood compared to those with a Typical Expressive temperament, and that family relationship stress would exacerbate this link. In an ongoing-longitudinal study of families with twins (N=563, 51% female, 29.8% Hispanic/Latinx, 58.4% White; Lemery-Chalfant et al., 2019), primary caregivers (PCs) reported on infant temperament at 12 months (IBQ; Gartstein & Rothbart, 2003, α=.74-.90). In a prior study (Murillo et al., 2023), latent profile analysis yielded three infant temperament types: Negative Dysregulated, Positive Well-Regulated, and Typical Expressive. PCs reported on partner strain (PSS; Schuster, Kessler, & Asseltine, 1990, α=.87) and family conflict (FCS; Porter & O’Leary, 1980, α=.80) at age 8 and a composite of these two measures represented Family Relationship Stress (r = .689). Confirmatory factor analysis was used to form Depression and Anxiety outcome composites based on PC (4 reports), secondary caregiver (2 reports), teacher (2 reports), and self-report (3 reports) measures of depression and anxiety symptoms collected from ages 8-11 (HBQ, Armstrong & Goldstein, 2003; BPI, Measelle et al., 1998, all α’s > .80). We randomly selected one twin from each pair and conducted regression analyses, and then used the second twin for an internal replication. Family relationship stress had a significant main effect on both anxiety and depressive symptoms. The Negative Dysregulated temperament type did not predict anxiety and depression at ages 8-11, however, it interacted with family relationship stress to predict anxiety and depression in 1 of 2 samples. When family relationship stress was low, the Negative Dysregulated type was significantly associated with higher anxiety and depression outcomes compared to the Typical Expressive type, and high family relationship stress was significantly associated with lower depression outcomes. Elucidating these longitudinal relations is important for informing early intervention and reducing the burden of adolescent psychopathology.

Chronic pain is common among children and can lead to future physical disability and health problems. The Biopsychosocial model of child pain suggests that biological, psychological, and social factors predict pain risk, but most research has focused on biological and psychological factors impacting child pain, and less on social factors. One social factor is family stress, including parent mental and physical health problems, and parenting and marital stress. The impact of stress, however, may vary depending on the presence of positive family resources, including marital empathy, parental warmth, and interpersonal support. Thus, the current longitudinal study examined links between family stress and increases in child pain during middle childhood and tested whether positive resources acted as a buffer to protect the development of child pain and if low social status acted as an extra stressor to make pain worse. Participants were part of the Arizona Twin Project, an ongoing longitudinal project of twins. At twin age 9, primary caregivers (PCs) reported on different stress, social status, and positive resources measures, and PCs and twins reported on twin bodily pain. At twin age 11, PCs and twins again reported on twin chronic bodily pain. Neither greater family stress nor parent physical health problems predicted increases in child pain over two years, controlling for twin pain at age 9. In tests of moderation, a single significant interaction emerged in a direction opposite of prediction: the relation between family stress and child pain was moderated by social status, such that average and high levels of social status exacerbated the relation between family stress, and child pain at age 11. Although the interaction needs to be replicated, findings suggest that high social status may act as a risk factor for poor child physical health and pain when family stress is high. Future research should further explore whether and how family stress and social status, as well as peer stress and resources, alone and in combination predict health as children age into adolescence.

The interconnection between family contexts and sleeping patterns play a crucial role in childhood development, with disturbances in either being indicative of future health outcomes in adulthood. It is unclear whether sibling relationships and sleep would have a similar effect as there are not many studies that have examined these links by using subjective sleep and sibling relationship assessments. Given this gap in the literature, the present studied aimed to 1) examine potential bidirectional relations between sibling relationships (warmth, conflict) and sleep variables (duration, efficiency, and sleep midpoint variability) across ages 8 and 10, and 2) test whether a novel sibling interaction task with measures of sharing and competition conducted at age 8 predicts sleep variables both cross sectionally and two years later at age 10. Data are from the Arizona Twin Project which includes a racially and socioeconomically diverse representation of children in Arizona. Twins wore an actigraph watch at both age 8 and age 10 to capture sleep duration and efficiency. Primary caregivers also reported sibling relationships via a questionnaire during both waves. Twins completed a marble pulling task to measure negotiation and cooperation behaviors at age 8 only. We tested cross-lagged prospective associations between sleep and sibling contexts. My study identified a longitudinal, positive association with sibling warmth at age 8 and sleep duration at age 10 and another concurrent, positive association with sibling conflict at age 8 and sleep midpoint variability at age 8. A negative association was identified between sibling warmth and sleep efficiency at age 10. Stability over time was also identified in both sleep variables and sibling relationships. Future studies can further investigate the different ways siblings may influence sleep behaviors, or vice versa, by taking into consideration the quality of the relationship, age, gender, and overall family dynamics. Due to the complexity of sibling relationships, the relations between sleep and siblings may vary among different individuals and families. These additional factors may need to be considered when evaluating the effects of sibling relationships and sleep on child development and well-being.

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.

Chronic pain is common during childhood and has negative immediate and long-term implications for physical and mental health. Prior research points to physical activity and sleep as protective health-promoting behaviors predicting lower chronic pain intensity and disability during adulthood. No study has yet examined the interaction of physical activity and sleep parameters in prediction of chronic pain in a community sample of children. Guided by the biopsychosocial model of pediatric chronic pain, this study explored objectively assessed physical activity and sleep patterns at age 8 as predictors of childhood chronic pain at age 9 in a racially/ethnically and socioeconomically diverse sample of 896 twins participating in the longitudinal Arizona Twin Project. It was hypothesized that parameters of physical activity levels and sleep health would independently predict chronic pain one year later, and that sleep parameters would moderate the association between physical activity and chronic pain. Monthly chronic pain was common, with 57.1% of participants reporting at least one pain location. Headaches, stomachaches, and backaches were the most frequent chronic pain presentations. Participants exceeded physical activity guidelines but did not meet sleep recommendations for their age group. Multilevel modeling analyses revealed that physical activity and sleep parameters at age 8 did not predict chronic pain one year later, and that sleep parameters did not moderate the associations between physical activity and chronic pain. The present study provides evidence that the associations between objectively assessed physical activity and sleep and chronic pain are not yet evident during middle childhood in this community sample compared to patient samples who have existing pain, suggesting that these health behaviors may play distinct roles in pain development versus pain management. They also point to the need to pinpoint the time frame during which these health behaviors become relevant and potentially interact to predict chronic pain development and maintenance. Longitudinal research tracking these health behaviors and pain using both subjective and objective methods as children transition into and through adolescence can help to identify optimal developmental stages at which to target prevention and intervention efforts to promote long term health.