The phenotypic associations and gene-environment underpinnings of socioeconomic status and diurnal cortisol secretion in adolescence.

While converging evidence suggests that both environmental and genetic factors underlie variations in diurnal cortisol, the extent to which these sources of influence vary according to socioeconomic status (SES) has seldom been investigated, particularly in adolescence. To investigate whether a distinct genetic and environmental contribution to youth's diurnal cortisol secretion emerges according to family SES and whether the timing of these experiences matters. Participants were 592 twin pairs, who mostly came from middle-income and intact families and for whom SES was measured in childhood and adolescence. Diurnal cortisol was assessed at age 14 at awakening, 30 min later, in the afternoon and evening over four nonconsecutive days. SES-cortisol phenotypic associations were specific to the adolescence period. Specifically, higher awakening cortisol levels were detected in wealthier backgrounds, whereas higher cortisol awakening response (CAR) and diurnal changes were present at both ends of the SES continuum. Moreover, smaller genetic contributions emerged for awakening cortisol in youth from poorer compared to wealthier backgrounds. The results suggest that the relative contribution of inherited factors to awakening cortisol secretion may be enhanced or suppressed depending on the socio-family context, which may help to decipher the mechanisms underlying later adjustment.

Working memory mediates the effects of gestational age at birth on expressive language development in children.

OBJECTIVE: This study tested the role of temporary memory, measured by phonological short-term memory (pSTM) and verbal working memory (vWM), as a mediator of the effect of 3 putative risk factors (i.e., socioeconomic status, home literacy environment, birth gestational age) upon expressive and receptive language. METHOD: A community-based sample of 646 Italian children aged 6-11 years was assessed with a comprehensive battery of language and cognitive tests. A mediation analysis was used to examine whether memory mediates environmental/biological effects on language. RESULTS: The results demonstrated a developmental cascade of effects, whereby the duration of pregnancy drives vWM functioning that, in turn, may affect expressive linguistic outcome Conclusion: Treatments focused on vWM, specifically to preterm children, may improve their language development, with enduring consequences on educational and psychosocial outcomes. (PsycINFO Database Record

Personal and familial predictors of peer victimization trajectories from primary to secondary school.

Using a sample of 767 children (403 girls, 364 boys), this study aimed to (a) identify groups with distinct trajectories of peer victimization over a 6-year period from primary school through the transition to secondary school, and (b) examine the associated personal (i.e., aggression or internalizing problems) and familial (family status, socioeconomic status, the parent-child relationship) predictors. Peer victimization was assessed via self-reports from Grades 4 through 9 (ages 10 through 15 years), aggression and internalizing problems were assessed in Grade 4 via peer nominations, and the parent-child relationship was assessed in Grade 7 (i.e., right after the transition to secondary school) via parent-reports. Growth Mixture modeling revealed 1 group (62%) who experienced little victimization in primary school and even less in secondary school, another group (31%) who was victimized in primary but not or much less in secondary school, and a third group (7%) who was chronically victimized in both school contexts. Boys were more likely than girls to follow any elevated victimization trajectory. Chronic victimization across primary and secondary school was predicted by nonintact family status and a combination of both internalizing problems and aggression compared with nonvictimized youth. In contrast, transitory victimization during primary but not in secondary school was predicted by aggression, but not internalizing problems. Support as well as conflict in the parent-child relationship also showed significant, albeit distinct associations with the different peer victimization trajectories. (PsycINFO Database Record

Gene-environment processes linking aggression, peer victimization, and the teacher-child relationship.

Aggressive behavior in middle childhood is at least partly explained by genetic factors. Nevertheless, estimations of simple effects ignore possible gene-environment interactions (G × E) or gene-environment correlations (rGE) in the etiology of aggression. The present study aimed to simultaneously test for G × E and rGE processes between aggression, on the one hand, and peer victimization and the teacher-child relationship in school, on the other hand. The sample comprised 124 MZ pairs and 93 DZ pairs assessed in Grade 1 (mean age = 84.7 months). Consistent with rGE, children with a presumed genetic disposition for aggression were at an increased risk of peer victimization, whereas in line with G × E, a positive relationship with the teacher mitigated the genetically mediated expression of aggression.

Closing the gap in academic readiness and achievement: the role of early childcare.

BACKGROUND: Socially disadvantaged children with academic difficulties at school entry are at increased risk for poor health and psychosocial outcomes. Our objective is to test the possibility that participation in childcare--at the population level--could attenuate the gap in academic readiness and achievement between children with and without a social disadvantage (indexed by low levels of maternal education). METHODS: A cohort of infants born in the Canadian province of Quebec in 1997/1998 was selected through birth registries and followed annually until 7 years of age (n = 1,863). Children receiving formal childcare (i.e., center-based or non-relative out-of-home) were distinguished from those receiving informal childcare (i.e., relative or nanny). Measures from 4 standardized tests that assessed cognitive school readiness (Lollipop Test for School Readiness), receptive vocabulary (Peabody Picture Vocabulary Test Revised), mathematics (Number Knowledge Test), and reading performance (Kaufman Assessment Battery for children) were administered at 6 and 7 years. RESULTS: Children of mothers with low levels of education showed a consistent pattern of lower scores on academic readiness and achievement tests at 6 and 7 years than those of highly educated mothers, unless they received formal childcare. Specifically, among children of mothers with low levels of education, those who received formal childcare obtained higher school readiness (d = 0.87), receptive vocabulary (d = 0.36), reading(d = 0.48) and math achievement scores (d = 0.38; although not significant at 5%) in comparison with those who were cared for by their parents. Childcare participation was not associated with cognitive outcomes among children of mothers with higher levels of education. CONCLUSIONS: Public investments in early childcare are increasing in many countries with the intention of reducing cognitive inequalities between disadvantaged and advantaged children. Our findings provide further evidence suggesting that formal childcare could represent a preventative means of attenuating effects of disadvantage on children's early academic trajectory.

Early child language mediates the relation between home environment and school readiness.

Home environment quality is a well-known predictor of school readiness (SR), although the underlying processes are little known. This study tested two hypotheses: (a) child language mediates the association between home characteristics (socioeconomic status and exposure to reading) and SR, and (b) genetic factors partly explain the association between language and SR. Data were collected between 6 and 63 months in a large sample of twins. Results showed that home characteristics had direct effects on SR and indirect effects through child language. No genetic correlation was found between language and SR. These results suggest that home characteristics affect SR in part through their effect on early language skills, and show that this process is mainly environmental rather than genetic in nature.

Variations in heritability of cortisol reactivity to stress as a function of early familial adversity among 19-month-old twins.

CONTEXT: Cortisol reactivity is a marker of vulnerability for a variety of stress-related diseases that likely arise from the contributions of both genetic and environmental sources of influence. However, little is known about gene-environment interplay in early cortisol reactivity. OBJECTIVES: To examine the genetic and environmental contributions to early cortisol reactivity in a population-based sample of 19-month-old twins and to determine whether these contributions vary as a function of early familial adversity. DESIGN: A variant of the twin method, with genetic and environment contributions to cortisol reactivity estimated as a function of familial adversity. Familial adversity was defined as the presence of 7 risk factors during perinatal and postnatal development (eg, at 6 and 19 months of age): maternal smoking during pregnancy, low birth weight, low family income, low maternal educational level, single parenthood, young motherhood, and maternal hostile or reactive behaviors. Twins exposed to 4 or more risk factors at either time were considered as having been exposed to high (vs low) familial adversity (23.4% of the sample). SETTING: Centre de Recherche Fernand-Seguin at the Hôpital Louis-Hyppolite Lafontaine, Montréal, Quebec. Patients Participants were families of twins from the Québec Newborn Twin Study recruited between April 1, 1995, and December 31, 1998, in the greater Montréal area. A total of 346 twins, 130 monozygotic and 216 dizygotic, were included in the study. MAIN OUTCOME MEASURES: Salivary cortisol samples were collected before and after the participating twins had been exposed to unfamiliar situations; change in cortisol over time was used as a measure of cortisol reactivity. RESULTS: Distinct patterns of genetic and environmental contributions to cortisol reactivity were evidenced as a function of familial adversity, suggesting a possible gene-environment interplay. In low-familial adversity settings that characterized most families, both genetic and unique but not shared environmental factors accounted for individual differences in cortisol reactivity, with shared genes explaining the similarity observed within twin pairs. By contrast, in conditions of high familial adversity, both shared and unique environmental factors, but not genetic factors, accounted for the variance in cortisol reactivity. CONCLUSION: This pattern of differing genetic and environmental contributions according to familial adversity suggests that, early in life, high familial adversity may have a programming developmental effect on cortisol reactivity.