Early temperamental and biological predictors of dimensions of social withdrawal in childhood

Social wariness and preference for solitude, two dimensions of social withdrawal, show unique associations with various socioemotional difficulties in childhood, including internalizing and peer problems. However, their early childhood predictors remain vastly undocumented. The present study aimed to examine whether early indicators of reactivity in situations of unfamiliarity such as behavioral inhibition, affect, and cortisol independently, or in interaction with emotion regulation as indexed by vagal tone, predict later social wariness and preference for solitude. Participants were 1209 children from the Quebec Newborn Twin Study. Vagal tone was assessed at 5 months, and behavioral inhibition, affect, and cortisol were assessed at 19 months in situations of unfamiliarity. Mothers, teachers, and peers evaluated social wariness and preference for solitude repeatedly from 4 to 10 years old. Findings show that three temperamental dimensions, social inhibition, nonsocial inhibition, and affect accounted for the variability in reactions to unfamiliarity. Behavioral inhibition to social unfamiliarity at 19 months predicted social wariness during the preschool years. Poor vagal regulation at 5 months exacerbated the risk associated with negative affect at 19 months to predict preference for solitude during the preschool years. Overall, results show that social wariness and preference for solitude may follow different developmental pathways.

Polygenic scores differentially predict developmental trajectories of subtypes of social withdrawal in childhood

BACKGROUND

Children who consistently withdraw from social situations face increased risk for later socioemotional difficulties. Twin studies indicate that genetic factors substantially account for the persistence of social withdrawal over time. However, the molecular genetic etiology of chronic courses of social wariness and preference for solitude, two dimensions of social withdrawal, remains undocumented. The objectives of the present study were (a) to identify high-risk trajectories for social wariness and preference for solitude in childhood and (b) to examine whether falling on these high-risk trajectories can be predicted by specific polygenic scores for mental health traits and disorders and by a general polygenic predisposition to these traits.

METHODS

Teachers evaluated 971 genotyped children at five occasions (age 6 to 12 years) from two prospective longitudinal studies, the Quebec Newborn Twin Study and the Quebec Longitudinal Study of Child Development. Developmental trajectories for social wariness and preference for solitude were identified. We tested whether polygenic scores for attention deficit hyperactivity disorder, autism spectrum disorder, depression, loneliness, and subjective well-being, as well as a general mental health genetic risk score derived across these traits, were associated with the developmental trajectories.

RESULTS

Polygenic scores differentially predicted social wariness and preference for solitude. Only the loneliness polygenic score significantly predicted the high trajectory for social wariness. By contrast, the general mental health genetic risk score factor was associated with the trajectory depicting high-chronic preference for solitude.

CONCLUSIONS

Distinct associations were uncovered between the polygenic scores, social wariness, and preference for solitude.

Developing a quality curriculum in a technological era

There is considerable rhetoric internationally around the need for national curricula to reflect the changes that are taking place in the world outside school. This raises questions about what a quality curriculum in a technological era should look like, and equally challenging issues about how to achieve the necessary changes in schooling in order for such a curriculum to be realised. This paper summarises the views of 11 experts from seven countries. It introduces a sociocultural framework that highlights the complexity of achieving alignment between policies and practice spanning the national to local school to classroom levels. Three key issues that underpin alignment are then explored, each of which link with the issue of trust:stakeholders engagement;teacher professionalism;summative assessment. By exploring and exemplifying these three issues the paper indicates potential ways of addressing them and provides 'tools to think with' to enhance future curriculum development initiatives.

Prenatal and childhood exposure to chlordecone and sex-typed toy preference of 7-year-old Guadeloupean children

Chlordecone was used intensively as an insecticide in the French West Indies. Because of its high persistence, the resulting contamination of food and water has led to chronic exposure of the general population as evidenced by its presence in the blood of people of Guadeloupe, in particular in pregnant women and newborns, and in maternal breast milk. Chlordecone is recognized as a reproductive and developmental toxicant, is neurotoxic and carcinogenic in rodents, and is considered as an endocrine-disrupting compound with well-established estrogenic and progestogenic properties both in vitro and in vivo. The question arises of its potential consequences on child neurodevelopment following prenatal and childhood exposure, in particular on behavioral sexual dimorphism in childhood. We followed 116 children from the TIMOUN mother-child cohort study in Guadeloupe, who were examined at age 7. These children were invited to participate in a 7-min structured play session in which they could choose between different toys considered as feminine, masculine, or neutral. The play session was video recorded, and the percentage of the time spent playing with feminine or masculine toys was calculated. We estimated associations between playtime and prenatal exposure to chlordecone (assessed by concentration in cord blood) or childhood exposure (determined from concentrations in child blood obtained at the 7-year follow-up), taking into account confounders and co-exposures to other environmental chemicals. We used a two-group regression model to take into account sex differences in play behavior. Our results do not indicate any modification in sex-typed toy preference among 7-year-old children in relation with either prenatal or childhood exposure to chlordecone.

Effects of polychlorinated biphenyls exposure on physical growth from birth to childhood and adolescence: A prospective cohort study

BACKGROUND/AIMS

Given that their traditional lifestyle and diet still relies on fish and other marine species for sustenance, the Inuit are highly exposed to polychlorinated biphenyls (PCBs) and PCBs are increasingly linked to obesity. However, evidence is not consistent regarding which periods of exposure are most relevant. In this study, we examine whether in utero, childhood, and adolescent exposure to PCBs are related to physical growth at adolescence.

METHOD

Inuit adolescents from Canada (N=212) enrolled in a prospective longitudinal cohort study since birth were assessed for height, weight, body mass index (BMI), fat mass index (FMI) and fat free mass index (FFMI) at 18 years of age. PCB 153 concentrations were quantified in blood samples obtained at birth (umbilical cord), 11, and 18 years of age. Maternal anthropometrics were measured and those for the newborns collected from medical records. Data on biological mothers and participants' sociodemographic characteristics and food security were collected using interviews. Multiple linear regression analyses were used to test associations between PCB 153 concentrations and adolescent anthropometric measures.

RESULTS

Cord PCB 153 was not related to height or FFMI at adolescence. By contrast, analyses showed that cord PCB 153 was related to higher BMI, FMI and marginally to weight in girls but not boys. Child PCB 153 was not related to height, weight or FFMI in adolescence. Child PCB 153 was related to lower BMI and FMI at adolescence in both sexes, particularly among those considered overweight or obese during childhood. Adolescent PCB 153 was not associated with any outcome.

CONCLUSION

This study suggests that prenatal exposure to PCBs may have a long-term effect on growth in early adulthood among girls and identifies the peri-pubertal period as another window of sensitivity for the action of PCBs. Our findings also suggest that exposure to PCBs and body size be documented in multiple time periods from infancy to adulthood.

Gestational Exposures to Phthalates and Folic Acid, and Autistic Traits in Canadian Children

BACKGROUND

The etiology of autism spectrum disorder is poorly understood. Few studies have investigated the link between endocrine-disrupting chemicals and autistic traits. We examined the relationship between gestational phthalates and autistic traits in 3- to 4-y-old Canadian children. We also investigated potential effect modification by sex and folic acid supplementation.

METHODS

We enrolled 2,001 women>18 years of age during the first trimester of pregnancy between 2008 and 2011 from 10 cities in Canada. At 3-4 years of age, 610 children underwent neuropsychological assessments including the Social Responsiveness Scale-II (SRS-2) as a measure of autistic traits and social impairment. We measured 11 phthalate metabolites in maternal first trimester urine samples and assessed folic acid supplementation from reported intakes. We estimated covariate-adjusted differences in SRS-2 T-scores with a doubling in phthalate concentrations in 510 children with complete data.

RESULTS

Mean total SRS T-score was 45.3 (SD=6.1). Children with higher gestational exposure to mono-n-butyl (MBP) and mono-3-carboxypropyl (MCPP) concentrations exhibited significantly higher total SRS T-scores, indicating greater overall social impairment, as well as higher scores on subdomains, indicating deficits in social cognition, social communication, social motivation, and restricted interests/repetitive behaviors. A doubling in MBP or MCPP concentrations was associated with 0.6 (95% CI: 0.1, 1.0) and 0.5 (95% CI: 0.1, 0.8) higher total SRS T-scores. Associations were consistently and significantly stronger in boys (βMBP=1.0; 95% CI: 0.4, 1.6; n=252) compared with girls (βMBP=0.1; 95% CI: -0.6, 0.7; n=258) and among children who had lower prenatal folic acid supplementation (<400μg/d) (βMBP=1.3; 95% CI: 0.4, 2.3; n=59) compared with those who had adequate folic acid supplementation (≥400μg/d) (βMBP=0.4; 95% CI: -0.1, 0.8; n=451).

CONCLUSIONS

Higher gestational concentrations of some phthalate metabolites were associated with higher scores of autistic traits as measured by the SRS-2 in boys, but not girls; these small size effects were mitigated by first trimester-of-pregnancy folic acid supplementation. https://doi.org/10.1289/EHP5621.

Association between early lead exposure and externalizing behaviors in adolescence: A developmental cascade

BACKGROUND

Lead (Pb) exposure is associated with adverse neurological development. Most notably, it has been observed through externalizing behavior symptoms, as observed among Inuit children from northern Québec. Evidence for a persistent neurological impact of early Pb exposure later in life is however scarce. Pb exposure may initiate a developmental cascade that increases the risk of long-term behavior problems.

OBJECTIVES

Testing for direct associations between childhood Pb concentrations and adolescent externalizing symptoms and substance use, as well as indirect associations through childhood behavior assessments.

METHODS

The study sample is a longitudinal cohort of Inuit children (n = 212) followed since birth. Blood Pb concentrations were measured during childhood (median age = 11.4 years) and adolescence (median age = 18.5 years). Externalizing/inattentive behavior were teacher-assessed through the Teacher Report Form and the Disruptive Behavior Disorders Rating Scale for children. At the adolescence follow-up, behavior problems were self-reported by filling Achenbach's Youth Self-Report, the Barkley Adult ADHD-IV Rating Scale, and the Diagnostics Interview Schedule for Children. Adolescent substance use was also self-assessed through the DEP-ADO. Direct and indirect associations of child Pb concentrations with adolescent outcomes were tested through mediation models.

RESULTS

Child blood Pb concentrations were not directly associated with any adolescent outcomes. On the contrary, childhood Pb exposure was indirectly associated, through childhood externalizing behavior assessments, with adolescent externalizing behaviors, binge drinking, and cannabis use. These indirect associations held after controlling for adolescents' concurrent Pb blood concentrations.

DISCUSSION

Our results highlight the indirect but lasting effects of child Pb exposure on adolescent behavior problems, and the importance of childhood externalizing behavior in this relationship. Adverse early-life environment put children on a riskier developmental trajectory, increasing their likelihood of lifelong psychological, social and health problems.

Household overcrowding and psychological distress among Nunavik Inuit adolescents: a longitudinal study

About half of Nunavik Inuit live in overcrowded households compared to very few Canadians from the general population. Living in overcrowded households is associated with greater risks of suffering from mental health problems for Canadian adolescents. The present work aims at studying prospectively the hypothesised relationship between household overcrowding at childhood and psychological distress during adolescence among Nunavik Inuit, as well as the hypothesised relationship between these phenomena when they are both measure at adolescence. Recruited as part of the Nunavik Child Development Study, 220 participants were met at 11 years old in average and then when they were 18 years old in average. Household overcrowding was assessed using the people per room ratio. Psychological distress symptoms were operationalised at adolescence using depressive symptoms and suicidal thoughts. The results did not show that childhood household crowding had a long-term effect on psychological distress. An absence of moderation by sex of the association was also found in the present study. Despite those results, household crowding could be a risk factor only when in interaction with other elements related with poverty or housing or could be experienced as a difficulty for adolescents on other aspects than depressive symptoms and suicidal thoughts.

Prenatal, concurrent, and sex-specific associations between blood lead concentrations and IQ in preschool Canadian children

BACKGROUND

Lead exposure predicts altered neurodevelopment and lower intelligence quotient (IQ) in children, but few studies have examined this association in children who have relatively low blood lead concentrations.

OBJECTIVES

To test the associations between blood lead concentrations and cognitive function in Canadian preschoolers, with a possible moderation by sex.

METHODS

The data were gathered from 609 mother-child pairs from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study. Lead was measured in umbilical and maternal blood, and in children's venous blood at age 3-4 years. Cognitive function was measured with the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III) at 3-4 years. We tested the relationship between WPPSI-III scores and blood lead concentrations with multiple linear regression, adding child sex as a moderator.

RESULTS

Median blood lead concentrations for the mother at 1st trimester and 3rd trimester of pregnancy, and for cord and child blood were 0.60 μg/dL, 0.58 μg/dL, 0.79 μg/dL and 0.67 μg/dL, respectively. We found no association between cord blood lead concentrations and WPPSI-III scores in multivariable analyses. However, cord blood lead concentrations showed a negative association with Performance IQ in boys but not in girls (B = 3.44; SE = 1.62; 95% CI: 0.82, 5.98). No associations were found between WPPSI-III scores and prenatal maternal blood or concurrent child blood lead concentrations.

CONCLUSIONS

Prenatal blood lead concentrations below 5 μg/dL were still associated with a decline in cognitive function in this Canadian cohort, but only for boys.

Prenatal, concurrent, and sex-specific associations between blood lead concentrations and IQ in preschool Canadian children

BACKGROUND

Lead exposure predicts altered neurodevelopment and lower intelligence quotient (IQ) in children, but few studies have examined this association in children who have relatively low blood lead concentrations.

OBJECTIVES

To test the associations between blood lead concentrations and cognitive function in Canadian preschoolers, with a possible moderation by sex.

METHODS

The data were gathered from 609 mother-child pairs from the Maternal-Infant Research on Environmental Chemicals (MIREC) Study. Lead was measured in umbilical and maternal blood, and in children's venous blood at age 3-4 years. Cognitive function was measured with the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III) at 3-4 years. We tested the relationship between WPPSI-III scores and blood lead concentrations with multiple linear regression, adding child sex as a moderator.

RESULTS

Median blood lead concentrations for the mother at 1st trimester and 3rd trimester of pregnancy, and for cord and child blood were 0.60 μg/dL, 0.58 μg/dL, 0.79 μg/dL and 0.67 μg/dL, respectively. We found no association between cord blood lead concentrations and WPPSI-III scores in multivariable analyses. However, cord blood lead concentrations showed a negative association with Performance IQ in boys but not in girls (B = 3.44; SE = 1.62; 95% CI: 0.82, 5.98). No associations were found between WPPSI-III scores and prenatal maternal blood or concurrent child blood lead concentrations.

CONCLUSIONS

Prenatal blood lead concentrations below 5 μg/dL were still associated with a decline in cognitive function in this Canadian cohort, but only for boys.

Prenatal exposure to polybrominated diphenyl ethers and predisposition to frustration at 7 months: Results from the MIREC study

BACKGROUND

Prenatal exposure to polybrominated diphenyl ethers (PBDEs) has been associated with cognitive deficits and behavioral problems in children. To date, no study has examined this exposure in association with neurobehavioral development in infants younger than 12 months assessed with observational tasks.

OBJECTIVES

This study examined the relation between prenatal PBDE concentrations and predisposition to frustration, assessed by the arm restraint task (ART), in Canadian infants.

METHODS

In a prospective longitudinal study conducted in Canada, exposure to nine PBDE congeners was measured in maternal plasma during the first trimester of pregnancy. The ART was used to measure predisposition to frustration in infancy (N = 333; mean age = 6.9 months), as assessed by negative vocalizations (crying and screaming) and physical reactivity (discomfort movements).

RESULTS

Maternal plasma PBDE-47 concentrations collected during pregnancy were associated with negative vocalizations using the ART (adjusted Relative Risk [aRR] = 1.04, 95% CI: 1.00, 1.09). Prenatal PBDE-99 concentrations during pregnancy were also related to a shift to the left in the tail of the distribution of onset of negative vocalizations as measured by a decrease of 38 s (95% CI: -78.1, 1.3) in the 75th quantile of the distribution for infants whose mothers had detectable levels of PBDE-99 compared to infants of mothers with undetectable levels. Similarly, infants whose mothers had detectable levels of PBDE-100 showed an increase of 24.1 s (95% CI: 4.1, 44.1) in the 75th quantile of the distribution of proportion of time in negative vocalizations compared with infants of mothers with undetectable levels. Finally, the association between PBDE-47 and PBDE-153, and physical reactivity was significantly modified by sex (p < 0.1), with opposite patterns in girls and boys.

CONCLUSIONS

Prenatal exposure to PBDEs was associated with increased incidence of crying and screaming with delayed onset of discomfort movement, which may indicate a predisposition to frustration and lack of habituation in infants younger than 12 months from the general population.

LINKS BETWEEN MATERNAL AND ADOLESCENTS’ CANNABIS USE AMONG THE INUIT OF NUNAVIK

BACKGROUND

Inuit from Nunavik, Northern Quebec, show some of the highest prevalence of cannabis use in the world, particularly for youths. Based on the ecological system theory, family (the more proximal unit to adolescents) is susceptible to influence their behaviors the most.

OBJECTIVES

The aim of this study was to examine, among the Inuit population from Nunavik, the association between maternal use of cannabis and the subsequent use of this substance by their children while adolescents.

DESIGN/METHODS

This study was based on longitudinal data from the Nunavik Child Development Study (endorsed by community and public health stakeholders; approved by ethic research boards from 2 North American Universities). We use data from two follow-ups, between 2005 and 2010 (T1: time 1 – children aged between 8–15 years-old), and between 2012 and 2016 (T2: time 2 – adolescents aged 16–21 years-old). Structured interviews were used to assess cannabis use and other concomitant variables among mothers at T1, and for adolescents at T2. Our final sample included 184 mother-adolescent dyads. Hypotheses that exposure to an increased frequency of maternal cannabis use at the end of childhood will be associated with 1) earlier initiation of cannabis during adolescence, and 2) will increase the frequency of cannabis use by youths, were tested with Cox regression analyses and ordinal regressions, taking into account socioeconomic status (T1), gender, and student status of adolescents(T2).

RESULTS

About seven out of ten Inuit adolescent participants reported having used cannabis during the previous year of T2, and about 45% of users consumed daily. Among the adolescents who answered the initiation age question, 60% had used it before reaching 14 years. Associations between mother’s frequency of cannabis use at T1 and 1) adolescents’ initiation age to cannabis and 2) adolescents’ frequency of cannabis use were not statistically significant. Higher socioeconomic status and student status were associated with lower risk of cannabis use by youths.

CONCLUSION

Among a group of adolescents where cannabis use is highly prevalent, we were unable to highlight the impact from maternal substance use on subsequent behavior of their children while adolescents. Yet, key determinants already known to influence cannabis use among southern populations seem to be also relevant to the Inuit population from Nunavik. Common Aboriginal wisdom that it takes a village to raise a child seems to apply to cannabis use as well.

Phenotypic and genetic associations between reading comprehension, decoding skills, and ADHD dimensions: evidence from two population-based studies

BACKGROUND

The phenotypic and genetic associations between decoding skills and ADHD dimensions have been documented but less is known about the association with reading comprehension. The aim of the study is to document the phenotypic and genetic associations between reading comprehension and ADHD dimensions of inattention and hyperactivity/impulsivity in early schooling and compare them to those with decoding skills.

METHODS

Data were collected in two population-based samples of twins (Quebec Newborn Twin Study - QNTS) and singletons (Quebec Longitudinal Study of Child Development - QLSCD) totaling ≈ 2300 children. Reading was assessed with normed measures in second or third grade. Teachers assessed ADHD dimensions in kindergarten and first grade.

RESULTS

Both decoding and reading comprehension were correlated with ADHD dimensions in a similar way: associations with inattention remained after controlling for the other ADHD dimension, behavior disorder symptoms and nonverbal abilities, whereas associations with hyperactivity/impulsivity did not. Genetic modeling showed that decoding and comprehension largely shared the same genetic etiology at this age and that their associations with inattention were mostly explained by shared genetic influences.

CONCLUSION

Both reading comprehension and decoding are uniquely associated with inattention through a shared genetic etiology.

Socioeconomic and Psychosocial Adversity in Inuit Mothers from Nunavik during the First Postpartum Year / ᐃᓄᓕᕆᓂᕐᒧᑦ ᐱᕙᓪᓕᐊᔪᓕᕆᓂᕐᒧᓪᓗ ᐊᒻᒪᓗ ᐃᓄᓕᕆᓂᒃᑯᑦ ᐃᓱᒪᑎᒍᓪᓗ ᐅᓇᒻᒥᓇᖅᑐᑦ ᓄᓇᕕᒻᒥᑦ ᐃᓄᓐᓄᑦ ᐊᓈᓇᐅᔪᓄᑦ ᐊᕐᕌᒎᑉ ᓯᕗᓪᓕᖅᐹᖓᓂᑦ ᐃᕐᓂᓯᒪᓕᖅᑎᓪᓗᒋᑦ

The postpartum year is a crucial period for child development and mother-child attachment. In a young and prolific population such as the Inuit from Nunavik (northern Quebec, Canada), postpartum maternal well-being is even more concerning. This study aims to document the prevalence and co-occurrence of socioeconomic and psychosocial risk factors in this population, and to use these factors to identify specific profiles of women. Data collection involved 176 mothers recruited during pregnancy and interviewed 12 months after delivery. Socioeconomic (age, education, single parenting, unemployment, welfare) and psychosocial (psychological distress, suicidal thoughts and attempts, spousal abuse, drug and alcohol use) risk factors were documented. Four high-risk conditions (socioeconomic precariousness, distress, domestic abuse, and substance use) were computed and considered in the analysis. Adversity was salient because most of the women (58%) simultaneously experience many high-risk conditions, with socioeconomic difficulties, distress, and spousal abuse being the most prevalent. Distinct profiles were identified: those without socioeconomic and psychosocial risk factors (30.8%) and those experiencing distress (69.2%). From the latter category, two specific profiles of distressed mothers emerged: single women coping with socioeconomic stressors (40.1%), and women with fewer financial difficulties but in an abusive relationship and more likely to use drugs or binge drink (29.1%). Our results support the need for preventive and public health programs in this population to improve maternal as well as infant wellbeing.ᐊᕐᕌᒍ ᓯᕗᓪᓕᖅᐹᖅ  ᐃᕐᓂᓯᒪᓕᖅᑐᓂ  ᐱᓪᓗᕆᓐᓂᖅᐸᐅᕗᖅ  ᐊᓈᓇᐅᔪᖅ  ᕿᑐᕐᖓᖓᓗ  ᐊᑕᐅᓯᐅᖃᑎᒌᓐᓂᖏᓐᓄᑦ.  ᓄᓇᕕᒻᒥᐅᑦ  ᐃᓄᐃᑦ  ᐃᓅᓱᑦᑎᓪᓗᒋᑦ  ᐊᒻᒪᓗ  ᓇᓗᓇᐃᔭᐃᑦᑎᐊᖅᑐᑎᒃ  ᑭᒃᑰᓂᖏᓐᓂᒃ  ᐃᓱᒫᓗᓇᖅᐳᖅ  ᐊᓈᓇᐅᔪᑦ  ᖃᓄᐃᓐᖏᓐᓂᖏᑦ  ᐃᕐᓂᕋᑖᖅᑐᒥᓂᐅᑎᓪᓗᒋᑦ.  ᐅᓇ  ᖃᐅᔨᓴᕐᓂᖅ  ᑐᕌᒐᖃᖅᑯᖅ  ᑎᑎᖅᑐᐃᔾᔪᑕᐅᓪᓗᓂ  ᐃᓄᓕᕆᓂᕐᒧᑦ  ᐱᕙᓪᓕᐊᓂᕐᒧᓪᓗ  ᐊᒻᒪᓗ  ᐃᓄᓕᕆᓂᕐᒧᑦ  ᐃᓱᒪᒃᑯᓪᓗ  ᐊᑦᑕᕐᓇᕈᑕᐅᔪᓂᒃ  ᐃᓄᓐᓄᑦ  ᐊᒻᒪᓗ  ᑖᒃᑯᐊ  ᐊᖅᑯᑎᒋᓗᒋᑦ  ᐊᕐᓇᐃᑦ  ᖃᓄᐃᑦᑑᓂᖏᑦ  ᐃᓕᓴᕐᓇᕈᑎᒋᓕᕐᓗᒋᑦ.  ᖃᐅᔨᒪᔾᔪᑎᓂᒃ  ᑲᑎᖅᓱᐃᓂᖅ  ᐃᓚᓕᐅᔾᔨᔪᕗᖅ  176−ᓂᒃ  ᐊᓈᓇᐅᔪᓂᒃ  ᐃᓚᓕᐅᑦᑐᒋᑦ  ᓇᔾᔨᔪᑦ  ᐊᒻᒪᓗ  ᐊᐱᖅᓱᖅᑕᐅᓯᒪᓪᓗᑎ  ᑕᖅᑮᑦ  ᖁᓕᑦ  ᒪᕐᕉᓪᓗ  (12)  ᐊᓂᒍᖅᓯᒪᓕᖅᑎᓪᓗᒋᑦ.  ᐃᓄᓕᕆᓂᖅ ᐱᕙᓪᓕᐊᓂᒃᑯᑦ  (ᐊᕐᕌᒍᒋᔭᖏᑦ,  ᐃᓕᓐᓂᐊᕐᓂᖏᑦ,  ᐃᓄᑑᔾᔨᓂᖅ,  ᐃᖅᑲᓇᐃᔮᖃᕐᓂᖅ,  ᓱᒃᑯᐊᕿᖃᑦᑕᕐᓂᖅ)  ᐊᒻᒪᓗ  ᐃᓱᒪᑎᒍᑦ  ᐃᓄᓕᕆᓂᒃᑯᑦ  (ᐃᓱᒫᓘᑕᐅᔪᑦ,  ᐃᒻᒥᓃᕈᒪᓂᖅ  ᐊᒻᒪᓗ  ᐃᒻᒥᓃᕋᓱᓐᓂᖅ,  ᓂᖓᕐᓂᖅ,  ᐋᖓᔮᕐᓇᑐᑦ  ᐊᒻᒪᓗ ᐃᒥᐊᓗᒻᒥᒃ  ᐊᑐᕐᓗᕐᓂᖅ)  ᑕᐃᒪᐃᑦᑐᑦ  ᐊᑦᑕᕐᓇᕈᑕᐅᔪᑦ  ᑎᑎᖅᑐᖅᑕᐅᓯᒪᕗᑦ.  ᑎᓴᒪᑦ ᖁᑦᑎᓂᖅᐹᑦ  ᐊᑦᑕᕐᓇᕈᑕᐅᔪᑦ  ᐊᑐᖅᑕᐅᔪᑦ (ᐃᓄᓕᕆᓂᕐᒧᑦ  ᐱᕙᓪᓕᐊᔪᓕᕆᓂᕐᒧᑦ  ᐊᑦᑐᐃᓗᖅᑯᑏᑦ,  ᐃᓱᒫᓗᒍᑎᑦ,  ᓂᖓᕐᓂᖅ  ᐊᒻᒪᓗ  ᓇᕐᓚᒍᑎᓂᒃ  ᐊᑐᕐᓂᕐᓗᒃ)  ᕿᒥᕐᕈᔭᐅᔪᔪᑦ  ᐊᒻᒪᓗ  ᐃᓱᒻᒥᕆᐊᕈᑕᐅᔪᔪᑦ  ᕿᒥᕐᕈᓂᒃᑯᑎᒍᑦ.  ᐊᑲᕐᕆᓐᖏᒍᑕᐅᔪᑦ  ᓲᔪᕐᓇᑦᑎᐊᔪᕗᑦ  ᐅᐱᓐᓇᕋᓂ  ᐃᓄᒋᐊᓐᓂᖅᓴᐃᑦ  ᐊᕐᓇᐃᑦ  (58%)  ᖁᑦᑎᓂᖅᐹᖑᔪᓂᑦ  ᐊᑦᑕᕐᓇᕈᑎᓂᑦ  ᐊᑐᖅᓯᒪᔪᑦ  ᐊᑲᐃᓪᓕᐅᕈᑎᖃᖅᑐᑎ  ᐃᓄᓕᕆᓂᕐᒧᑦ  ᐱᕙᓪᓕᐊᔾᔪᑎᒃᑯᑦ,  ᐃᓱᒫᓘᑎᖃᐅᖅᑐᑎ  ᐊᒻᒪᓗ  ᓂᖓᖅᑕᐅᓂᒃᑯᑦ  ᓲᔪᕐᓇᓛᖑᔪᓪᓗᑎ.  ᐊᔾᔨᒌᓐᖏᒍᑕᐅᔪᓪᓗ  ᓲᔪᕐᓇᖅᓯᔪᕗᑦ:  ᑕᐃᒃᑯᐊ  ᐃᓄᓕᕆᓂᒃᑯᑦ  ᐱᕙᓪᓕᐊᔪᓕᕆᓂᒃᑯᑦ  ᐊᒻᒪᓗ  ᐃᓱᒪᒃᑯᑦ  ᐃᓄᓕᕆᓂᒃᑯᑦ  ᐊᑦᑕᕐᓇᕈᑎᖃᓐᖏᑦᑐᑦ (30.8%)  ᐊᒻᒪᓗ  ᐅᖁᒪᐃᓪᓕᐅᖅᑐᑦ  (69.2%).  ᑭᖑᓪᓕᐅᔪᒥᒃ  ᖃᐅᔨᔾᔪᑎᒥᒃ,  ᒪᕐᕈᐃᓕᖅᑲᖓᔫᒃ  ᐃᓕᓴᕐᓇᖅᓯᔪᕘᒃ  ᐊᓈᓇᐅᔪᓄᑦ  ᐅᖁᒪᐃᓪᓕᐅᕈᑕᐅᔪᑦ:  ᐃᓄᑑᔾᔨᔪᑦ  ᐊᕐᓇᐃᑦ  ᐃᓄᓕᕆᓂᒃᑯᑦ  ᐱᕙᓪᓕᐊᓂᒃᑯᑦ  ᐃᓱᒫᓘᑎᓖᑦ  (40.1%)  ᐊᒻᒪᓗ  ᐊᕐᓇᐃᑦ  ᐃᓱᒫᓘᑎᖃᓐᖏᓂᔅᓴᐃᑦ  ᑮᓇᐅᔭᑎᒍᑦ  ᑭᓯᐊᓂᓕ  ᓂᖓᖅᑕᐅᕙᑦᑐᑦ  ᐊᒻᒪᓗ  ᐋᖓᔮᕐᓇᑐᖅᑐᐸᑦᑐᑦ  ᐅᕝᕙᓗᑭᐊᖅ  ᐃᒥᕋᓚᑉᐸᑦᑐᑦ  (29.1%).  ᖃᐅᔨᔾᔪᑎᕗᑦ  ᐃᑲᔪᖅᑐᐃᕗᑦ  ᑭᓐᖒᒪᔭᐅᔪᓂᒃ  ᓄᖅᑲᐅᒥᔾᔪᑎᔅᓴᑦ  ᐊᒻᒪᓗ  ᐃᓄᓐᓅᓕᖓᔪᓂᒃ  ᐃᓗᓯᓕᕆᓂᕐᒧᑦ  ᐃᖏᕐᕋᑎᑕᒐᕐᓂᒃ  ᐱᕚᓪᓕᐊᓂᒃᑯᑦ  ᐊᓈᓇᐅᔪᓄᑦ  ᐊᒻᒪᓗ  ᓄᑕᕋᖏᑕ  ᐃᓅᑦᑎᐊᕐᓂᖏᓐᓄᑦ.

Why children differ in motivation to learn: Insights from over 13,000 twins from 6 countries

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Genes rather than environment contribute to family resemblance in academic motivation.

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Environmental influences stemmed entirely from individual specific experiences.

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Attending same vs. different classes did not affect twin similarity in motivation.

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Results are similar across ages, countries and academic subjects.

Little is known about why people differ in their levels of academic motivation. This study explored the etiology of individual differences in enjoyment and self-perceived ability for several school subjects in nearly 13,000 twins aged 9–16 from 6 countries. The results showed a striking consistency across ages, school subjects, and cultures. Contrary to common belief, enjoyment of learning and children’s perceptions of their competence were no less heritable than cognitive ability. Genetic factors explained approximately 40% of the variance and all of the observed twins’ similarity in academic motivation. Shared environmental factors, such as home or classroom, did not contribute to the twin’s similarity in academic motivation. Environmental influences stemmed entirely from individual specific experiences.

Impact of Inuit customary adoption on behavioral problems in school-age Inuit children

A large proportion of Inuit children in Arctic Quebec are adopted in accordance with traditional Inuit customs. In contrast to adoptions in Southern Canada and the United States, the child is adopted at birth and by a close family member; he or she knows who his or her biological parents are, and will typically have contact with them. Studies of other populations have reported an increased incidence of behavior problems in adopted compared with nonadopted children. This study examined the actual extent of the increase in the number of behavior problems seen in Inuit children adopted in accordance with traditional customs. In a prospective longitudinal study conducted in the Canadian Arctic (n = 46 adopted and 231 nonadopted children), prenatal and familial variables were documented at birth and at school age (M = 11.3 years). Behavior problems were assessed on the Teacher Report Form of the Child Behavior Checklist. Adopted children lived in more economically disadvantaged families, but their caregivers were less prone to depression, domestic violence, or alcohol abuse compared with those of the nonadopted children. The adoption status was not related to the teacher's report of attention problems, externalizing or internalizing behaviors, after controlling for confounders. Despite less favorable socioeconomic circumstances, a higher extent of behavioral problems was not seen at school age in Inuit children adopted at birth by a family member. Psychosocial stressors associated with adoption are more likely to be responsible for an association with higher levels of childhood behavior problems rather than adoption per se.

Growth in Inuit children exposed to polychlorinated biphenyls and lead during fetal development and childhood

BACKGROUND

Because of their geographical location and traditional lifestyle, Canadian Inuit children are highly exposed to polychlorinated biphenyls (PCBs) and lead (Pb), environmental contaminants that are thought to affect fetal and child growth. We examined the associations of these exposures with the fetal and postnatal growth of Inuit children.

METHODS

We conducted a prospective cohort study among Inuit from Nunavik (Arctic Québec). Mothers were recruited at their first prenatal visit; children (n=290) were evaluated at birth and at 8-14 years of age. Concentrations of PCB 153 and Pb were determined in umbilical cord and child blood. Weight, height and head circumference were measured at birth and during childhood.

RESULTS

Cord blood PCB 153 concentrations were not associated with anthropometric measurements at birth or school age, but child blood PCB 153 concentrations were associated with reduced weight, height and head circumference during childhood. There was no association between cord Pb levels and anthropometric outcomes at birth, but cord blood Pb was related to smaller height and shows a tendency of a smaller head circumference during childhood.

INTERPRETATION

Our results suggest that chronic exposure to PCBs during childhood is negatively associated with skeletal growth and weight, while prenatal Pb exposure is related to reduced growth during childhood. This study is the first to link prenatal Pb exposure to poorer growth in school-age children.

Associations between prenatal cigarette smoke exposure and externalized behaviors at school age among Inuit children exposed to environmental contaminants

BACKGROUND

Smoking during pregnancy is common among Inuit women from the Canadian Arctic. Yet prenatal cigarette smoke exposure (PCSE) is seen as a major risk factor for childhood behavior problems. Recent data also suggest that co-exposure to neurotoxic environmental contaminants can exacerbate the effects of PCSE on behavior. This study examined the association between PCSE and behavior at school age in a sample of Inuit children from Nunavik, Québec, where co-exposure to environmental contaminants is also an important issue. Interactions with lead (Pb) and mercury (Hg), two contaminants associated with behavioral problems, were also explored.

METHODS

Participants were 271 children (mean age=11.3years) involved in a prospective birth-cohort study. PCSE was assessed through maternal recall. Assessment of child behavior was obtained from the child's classroom teacher on the Teacher Report Form (TRF) and the Disruptive Behavior Disorders Rating Scale (DBD). Exposure to contaminants was assessed from umbilical cord and child blood samples. Other confounders were documented by maternal interview.

RESULTS

After control for contaminants and confounders, PCSE was associated with increased externalizing behaviors and attention problems on the TRF and higher prevalence of attention deficit hyperactivity disorder (ADHD) assessed on the DBD. No interactions were found with contaminants.

INTERPRETATION

This study extends the existing empirical evidence linking PCSE to behavioral problems in school-aged children by reporting these effects in a population where tobacco use is normative rather than marginal. Co-exposure to Pb and Hg do not appear to exacerbate tobacco effects, suggesting that these substances act independently.

Genetic and environmental influences on daytime and nighttime sleep duration in early childhood

OBJECTIVES

To determine the relative contributions of genetic and environmental factors on daytime and nighttime continuous sleep duration at 6, 18, 30, and 48 months of age, and to identify different subgroups of children who followed different daytime and nighttime sleep duration trajectories and to investigate their etiology.

METHODS

The current study included 995 twins (405 monozygotic and 586 dizygotic) of the Quebec Newborn Twin Study recruited from the birth records of the Quebec Statistics Institute. Daytime and nighttime sleep was assessed through maternal reports at 6, 18, 30, and 48 months of age. A semiparametric modeling strategy was used to estimate daytime and nighttime sleep duration trajectories. Quantitative genetic models were used to examine to what extent genetic and environmental factors influenced daytime and nighttime continuous sleep duration.

RESULTS

Genetic modeling analyses revealed environmental influences for all daytime sleep duration trajectories. In contrast, strong genetic influences were found for consolidated nighttime sleep duration (except at 18 months and for the short-increasing sleep duration trajectory).

CONCLUSIONS

This is the first indication that early childhood daytime sleep duration may be driven by environmental settings, whereas the variance in consolidated nighttime sleep duration is largely influenced by genetic factors with a critical environmental time-window influence at ∼18 months.

Exposure to organochlorines and mercury through fish and marine mammal consumption: associations with growth and duration of gestation among Inuit newborns

BACKGROUND

Several studies have reported negative associations of polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB) and mercury (Hg) with duration of gestation and fetal growth in fish eating populations. Docosahexaenoic acid (DHA) from fish, seafood and marine mammal intake has been reported to be positively related with pregnancy duration and fetal growth. So far, it remains unclear, however, if the associations of environmental contaminants (ECs) with growth are direct or mediated through their relation with the duration of gestation and the degree to which DHA intake during pregnancy attenuates the negative association of ECs with fetal growth.

OBJECTIVES

To investigate direct and indirect associations of in utero exposure to ECs with fetal growth and pregnancy duration while taking into account the possible positive effects of DHA.

METHODS

Pregnant Inuit women (N=248) from Arctic Quebec were recruited and cord blood samples were analyzed for PCBs, HCB, Hg and DHA. Anthropometric measurements were assessed at birth. Path models were used to evaluate direct and indirect associations.

RESULTS

Cord concentrations of PCB 153, HCB and Hg were significantly associated with shorter duration of pregnancy (β varying from -0.17 to -0.20, p<0.05). Path models indicated that the associations of PCBs, HCB and Hg with reduced fetal growth (β varying from -0.09 to -0.13, p<0.05) were mediated through their relations with shorter gestation duration. Cord DHA was indirectly related to greater growth parameters (β varying from 0.17 to 0.20, p<0.05) through its positive association with gestation duration.

CONCLUSION

Prenatal exposure to ECs was associated with reduced gestation duration, which is a recognized determinant of fetal growth. DHA intake during pregnancy appeared to have independent positive association with fetal growth by prolonging gestation. Whether these associations are causal remains to be elucidated.

Prenatal methylmercury, postnatal lead exposure, and evidence of attention deficit/hyperactivity disorder among Inuit children in Arctic Québec

BACKGROUND

Prenatal exposure to methylmercury (MeHg) and polychlorinated biphenyls (PCBs) has been associated with impaired performance on attention tasks in previous studies, but the extent to which these cognitive deficits translate into behavioral problems in the classroom and attention deficit/hyperactivity disorder (ADHD) remains unknown. By contrast, lead (Pb) exposure in childhood has been associated with ADHD and disruptive behaviors in several studies.

OBJECTIVES

In this study we examined the relation of developmental exposure to MeHg, PCBs, and Pb to behavioral problems at school age in Inuit children exposed through their traditional diet.

METHODS

In a prospective longitudinal study conducted in the Canadian Arctic, exposure to contaminants was measured at birth and at school age. An assessment of child behavior (n = 279; mean age = 11.3 years) was obtained from the child's classroom teacher on the Teacher Report Form (TRF) from the Child Behavior Checklist, and the Disruptive Behavior Disorders Rating Scale (DBD).

RESULTS

Cord blood mercury concentrations were associated with higher TRF symptom scores for attention problems and DBD scores consistent with ADHD. Current blood Pb concentrations were associated with higher TRF symptom scores for externalizing problems and with symptoms of ADHD (hyperactive-impulsive type) based on the DBD.

CONCLUSIONS

To our knowledge, this study is the first to identify an association between prenatal MeHg and ADHD symptomatology in childhood and the first to replicate previously reported associations between low-level childhood Pb exposure and ADHD in a population exposed to Pb primarily from dietary sources.

Contribution of temporal processing skills to reading comprehension in 8-year-olds: evidence for a mediation effect of phonological awareness

This study tested whether the association between temporal processing (TP) and reading is mediated by phonological awareness (PA) in a normative sample of 615 eight-year-olds. TP was measured with auditory and bimodal (visual-auditory) temporal order judgment tasks and PA with a phoneme deletion task. PA partially mediated the association between both auditory and bimodal TP and reading, above nonverbal abilities, vocabulary, and processing speed. PA explained a larger proportion of the association between auditory TP and reading (56% vs. 39% for bimodal TP), and most of the association between bimodal TP and reading was direct. This finding is consistent with a dual-phonological and visual-pathway model of the association between TP and reading in normative reading skills.

Associations between sleep-wake consolidation and language development in early childhood: a longitudinal twin study

STUDY OBJECTIVES

The objectives were (1) to assess associations between sleep consolidation at 6, 18 and 30 months and language skills at 18, 30, and 60 months; and (2) to investigate the genetic/environmental etiology of these associations.

DESIGN

Longitudinal study of a population-based twin cohort.

PARTICIPANTS

1029 twins from the Quebec Newborn Twin Study.

MEASUREMENTS AND RESULTS

Sleep consolidation was derived from parental reports of day/night consecutive sleeping durations. Language skills were assessed with the MacArthur Communicative Development Inventory at 18 and 30 months and the Peabody Picture Vocabulary Test at 60 months. The day/night sleep ratio decreased significantly from 6 to 30 months. The 6- and 18-month ratios were negatively correlated with subsequent language skills. Children with language delays at 60 months had less mature sleep consolidation at both 6 and 18 months than children without delays and those with transient early delays. Genetic and regression analyses revealed that the sleep ratio at 6 months was highly heritable (64%) and predicted 18-month (B = -0.06) and 30-month language (B = -0.11) mainly through additive genetic influences (R(Gs) = 0.32 and 0.33, respectively). By contrast, the sleep ratio at 18 months was mainly due to shared environment influences (58%) and predicted 60-month language (B = -0.08) through shared environment influences (R(Cs) = 0.24).

CONCLUSIONS

Poor sleep consolidation during the first 2 years of life may be a risk factor for language learning, whereas good sleep consolidation may foster language learning through successive genetic and environmental influences.

De novo truncating mutation in Kinesin 17 associated with schizophrenia

BACKGROUND

Schizophrenia (SCZ) is one of the most disabling psychiatric disorders. It is thought to be due to a complex interplay between polygenic and various environmental risk factors, although recent reports on genomic copy number variations suggest that a fraction of the cases could result from variably penetrant de novo variants. The gene encoding the synaptic motor protein kinesin 17 (KIF17) involved in glutamatergic synapse is a candidate gene for SCZ.

METHODS

As part of our Synapse to Disease project, we resequenced KIF17 in a cohort of individuals with sporadic SCZ (188 subjects). Additional populations included autism spectrum disorder (142 subjects), nonsyndromic mental retardation (95 subjects), and control subjects (568 subjects). Functional validation of the human mutation was done in developing zebrafish.

RESULTS

Here we report the identification of a de novo nonsense truncating mutation in one patient with SCZ, in kinesin 17, a synaptic motor protein. No de novo or truncating KIF17 mutations were found in the additional samples. We further validated the pathogenic nature of this mutation by knocking down its expression in zebrafish embryos, which resulted in a developmental defect.

CONCLUSIONS

Together our findings suggest that disruption of KIF17, although rare, could result in a schizophrenia phenotype and emphasize the possible involvement of rare de novo mutations in this disorder.

A longitudinal twin study of the genetic and environmental etiology of maternal hostile-reactive behavior during infancy and toddlerhood

Children's negative characteristics are thought to be a factor in evoking hostile parenting responses. This can result in genotype/environment correlations (rGE) in which children's heritable traits influence the parenting they experience. We did genetic analyses on 292 mothers' self-reported hostile-reactive behaviors toward each of their twins at 5, 18 and 30 months. Finding heritability for a parenting behavior analyzed as a child phenotype is evidence of rGE correlation. The heritability of maternal behavior was modest (29% at 5 months, 0% at 18 months, and 25% at 30 months) and longitudinal analyses indicated that genetic factors at 5 and 30 months were uncorrelated. Common environment factors, probably reflecting characteristics of the mothers, were the main source of variance at the three ages and were highly correlated through time. We concluded that children's heritable characteristics evoked maternal negative response at specific times, but were not responsible for the stability of maternal hostility from infancy to toddlerhood.

Diagnosing zygosity in infant twins: physical similarity, genotyping, and chorionicity

We compared the results of different methods for diagnosing zygosity in a sample of 237 same-sex pairs of twins assessed at 5 and 18 months of age. Despite the twins' very young age and early stage of development, physical similarity was concordant with genotyping in 91.9% of cases at 5 months and 93.8% of cases at 18 months, for a subsample of 123 and 113 pairs, respectively. This concordance rate was obtained following a case-by-case assessment of each pair's physical similarity using a shortened version of the Zygosity Questionnaire for Young Twins (Goldsmith, 1991). Taking into account the chorionicity data available from the twins' medical files, we were able to classify correctly 96% of the pairs, an accuracy rate comparable to previously reported rates obtained with older twins. Chorionicity data is especially useful since we found that monochorionic MZ twins are more difficult than dichorionic MZ twins to diagnose by physical similarity at these young ages. The relative cost-benefit of methods based on reported physical similarity and DNA analysis is discussed in light of these results.