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Background: Exposure to peer victimization is relatively common. However, little is known about its developmental course and its effect on impairment associated with mental illnesses. We aimed to identify groups of children following differential trajectories of peer victimization from ages 6 to 13 years and to examine predictive associations of these trajectories with mental health in adolescence.Methods: Participants were members of the Quebec Longitudinal Study of Child Development, a prospective cohort of 2120 children born in 1997/98 who were followed until age 15 years. We included 1363 participants with self-reported victimization from ages 6 to 13 years and data available on their mental health status at 15 years.Results: We identified 3 trajectories of peer victimization. The 2 prevailing groups were participants with little or moderate exposure to victimization (441/1685 [26.2%] and 1000/1685 [59.3%], respectively); the third group (244 [14.5%]) had been chronically exposed to the most severe and long-lasting levels of victimization. The most severely victimized individuals had greater odds of reporting debilitating depressive or dysthymic symptoms (odds ratio [OR] 2.56, 95% confidence interval [CI] 1.27-5.17), debilitating generalized anxiety problems (OR 3.27, CI 1.64-6.51) and suicidality (OR 3.46, CI 1.53-7.81) at 15 years than those exposed to the lowest levels of victimization, after adjustment for sex, childhood mental health, family hardship and victimization perpetration. The association with suicidality remained significant after controlling for concurrent symptoms of depression or dysthymia and generalized anxiety problems.Interpretation: Adolescents who were most severely victimized by peers had an increased risk of experiencing severe symptoms consistent with mental health problems. Given that peer victimization trajectories are established early on, interventions to reduce the risk of being victimized should start before enrolment in the formal school system. [ABSTRACT FROM AUTHOR]

Purpose: Poverty has been associated with high levels of behavior problems across childhood, yet patterns of associations over time remain understudied. This study aims: (a) to examine whether poverty predicts changes in behavior problems between 1.5 and 8 years of age; (b) to estimate potential selection bias for the observed associations.Methods: We used the 1998-2006 waves of the Quebec Longitudinal Study of Child Development (N = 2120). Main outcomes were maternal ratings of hyperactivity, opposition and physical aggression from 1.5 to 8 years of age. Linear mixed-effects models were used to assess the longitudinal association between poverty and behavior problems. Models were re-estimated adjusting for wave nonresponse and using multiple imputation to account for attrition.Results: Poverty predicted higher levels of behavior problems between 1.5 and 8 years of age. Poverty predicted hyperactivity and opposition in a time dependent manner. Hyperactivity [Bpoverty*age = 0.052; CI 95 % (0.002; 0.101)] and opposition [Bpoverty*age = 0.049; CI 95 % (0.018; 0.079)] increased at a faster rate up to age 5 years, and then decreased at a slower rate for poor than non-poor children. Physical aggression decreased at a steady rate over time for all children [Bpoverty*age = -0.030; p = 0.064). Estimates remained similar when accounting for attrition.Conclusion: Poverty predicted higher levels of behavior problems between 1.5 and 8 years of age. The difference between poor and non-poor children was stable over time for physical aggression, but increased with age for hyperactivity and opposition. Attrition among poor children did not compromise the validity of results. [ABSTRACT FROM AUTHOR]

Comorbidity is frequent among disruptive behaviors (DB) and leads to mental health problems during adolescence and adulthood. However, the early developmental origins of this comorbidity have so far received little attention. This study investigated the developmental comorbidity of three DB categories during early childhood: hyperactivity-impulsivity, non-compliance, and physical aggression. Joint developmental trajectories of DB were identified based on annual mother interviews from age 1½ to 5 years, in a population-representative birth-cohort (N = 2045). A significant proportion of children (13 % to 21 %, depending on the type of DB) consistently displayed high levels of hyperactivity-impulsivity, non-compliance, or physical aggression from age 1½ to 5 years. Developmental comorbidity was frequent, especially for boys: 10 % of boys and 3.7 % of girls were on a stable trajectory with high levels of symptoms for the three categories of DB. Significant associations were observed between preschool joint-trajectories of DB and indicators of DB and school adjustment assessed by teachers in first grade. Preschoolers who maintained high levels of hyperactivity-impulsivity, non-compliance, and physical aggression, displayed the highest number of DB symptoms in first grade for all categories according to their teacher. They were also among the most disadvantaged of their class for school adjustment indicators. Thus, DB manifestations and developmental comorbidity of DB are highly prevalent in infancy. Early childhood appears to be a critical period to prevent persistent and comorbid DB that leads to impairment at the very beginning of school attendance and to long-term serious health and social adjustment problems. [ABSTRACT FROM AUTHOR]

This study investigated the evolving relations between peer victimization and social/emotional difficulties in middle to late childhood. Peer assessments of peer victimization and social/emotional difficulties (aggressive behavior, social withdrawal, and emotional vulnerability) were collected over 4 years for 1,035 children attending Grades 3-6 and were analyzed via cross-lagged panels and trajectory analyses. All dimensions were highly stable and significantly related initially. Peer victimization became progressively less related to aggression and increasingly associated with withdrawal. Bidirectional contributions over 1-year periods were found between withdrawal and emotional vulnerability and victimization. Trajectory analyses revealed heterogeneity in peer victimization patterns, with a small group of children (4.5%) being extremely victimized and with another group (10%), less severely, but increasingly victimized over time. Compared to nonvictimized children, these children were generally more emotional and became less aggressive but more socially withdrawn over time. These small behavioral changes were not associated with decreases in victimization. [ABSTRACT FROM AUTHOR]

Background: Disregard for rules, an important dimension of oppositional defiant and conduct disorders, is frequent during early childhood, but the development of its chronic form has not been studied during this key socialization period. This study aimed to describe the developmental trajectories of disregard for rules during early childhood and identify prenatal and postnatal predictors for a high trajectory. Methods: Participants were involved in a longitudinal study of a birth cohort followed yearly from 5 to 74 months of age ( N = 1,942). Prenatal and postnatal predictors were measured by parental report at the beginning of the study, and parents reported child disregard for rules at five time points from 29 to 74 months of age. Results: Four groups of children followed distinct and stable trajectories of mother-rated disregard for rules: Very Low (approximately 9.1%), Low (56.9%), Moderate (29.7%) and Chronic (4.3%). As expected, male sex was a significant predictor of the chronic trajectory (OR = 1.76, CI = 1.09–2.83). Mothers’ history of antisocial behavior (OR = 1.72, CI = 1.02–2.91), and postnatal depressive symptoms experienced by the mother (OR = 1.71, CI = 1.03–2.84) and the father (OR = 2.02, CI = 1.10–3.71) were also important independent predictors. However, contrary to expectations, children’s difficult temperament and parenting at 5 months did not predict chronic disregard for rules beyond other risk factors. Conclusions: High disregard for rules is fairly stable during early childhood and is associated with risk factors identifiable before and shortly after birth which may be used for targeted prevention. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

This study compared the contribution of genes and environment to teacher-rated reactive and proactive aggression in 6-year-old twin pairs (172 pairs: 55 monozygotic girls, 48 monozygotic boys, 33 dizygotic girls, 36 dizygotic boys). Genetic effects accounted for 39% of the variance of reactive aggression and for 41% of the variance of proactive aggression. The remainder of the variance was explained by unique environmental effects. Genetic as well as unique environmental effects were significantly correlated across reactive and proactive aggression (genetic correlation = .87, environmental correlation = .34), but this overlap was largely due to a common underlying form of aggression (i.e., teacher-rated physical aggression). Once common etiological factors due to physical aggression were accounted for, reactive and proactive aggression shared no other genes and only a few environmental influences, although additional specific genetic and environmental effects were observed for both reactive and proactive aggression. These specific effects indicate that both reactive and proactive aggression may be influenced mostly by socialization experiences that are specific to each type of aggression and only to a very small degree by specific genes. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Background: Genetic risk for depressive behavior may increase the likelihood of exposure to environmental stressors (gene–environment correlation, rGE). By the same token, exposure to environmental stressors may moderate the effect of genes on depressive behavior (gene–environment interaction, G×E). Relating these processes to a peer-related stressor in childhood, the present study examined (1) whether genetic risk for depressive behavior in children is related to higher levels of rejection by the peer group (rGE) and (2) whether peer rejection moderates the effect of genetic factors on children’s depressive behavior (G×E). Methods: The sample comprised 336 twin pairs (MZ pairs = 196, same-sex DZ pairs = 140) assessed in kindergarten (mean age 72.7 months). Peer acceptance/rejection was measured via peer nominations. Depressive behavior was measured through teacher ratings. Results: Consistent with rGE, a moderate overlap of genetic effects was found between peer acceptance/rejection and depressive behavior. In line with G×E, genetic effects on depressive behavior varied across levels of peer acceptance/rejection. Conclusions: An increased genetic disposition for depressive behavior is related to a higher risk of peer rejection (rGE). However, genes play a lesser role in explaining individual differences in depressive behavior in rejected children than in accepted children (G×E). [ABSTRACT FROM AUTHOR]

The purpose of this study was to test children's academic self-concept, family socioeconomic status, family structure (single parent vs. two parent family) and academic achievement in elementary school as predictors of children's educational attainment level in young adulthood within a ten-year longitudinal design. Participants (254 girls, 211 boys) were three cohorts of students in Grades 3, 4, and 5 from ten elementary schools. Results from structural equation modeling revealed that academic self-concept predicted educational attainment level ten years later over and above prior achievement. Moreover, this pattern of results was invariant across cohorts. In addition, regression analyses based on a restricted sample (n = 243) indicated that the academic self-concept/educational attainment level relation was still significant while controlling for family SES, family structure (single parent vs. two parent family), and academic achievement. Discussion focuses on the theoretical and practical implications of the results. [ABSTRACT FROM AUTHOR]

This study investigates emotion recognition deficits as candidate neurocognitive endophenotypes for callous-unemotional (CU) behaviors. Using a twin design, we tested genetic correlations between child CU behaviors and poor processing of fearful and sad facial expressions. Participants were 504 twin pairs (209 MZ pairs; 295 DZ pairs) from the Quebec Newborn Twin Study, a longitudinal study of a population-based sample of twins. Teachers in kindergarten and first grade rated children's CU behaviors and other behavior problems (attention deficit and hyperactivity symptoms, physical aggression, and depressive symptoms). In first grade (mean age 7 years), the children completed the visual subtest of the Diagnostic Analysis of Nonverbal Accuracy Scale 2 (DANVA-II) to assess emotion recognition from facial stimuli. Using structural equation modeling, we examined the genetic-environmental etiology of the association between fear/sadness recognition and child CU behaviors, controlling for other behavior problems and recognition of other emotions. We found a significant genetic correlation between poor fear recognition and CU behaviors that was independent of other behavior problems. Poor recognition of sadness was not significantly associated with CU behaviors after taking into account other behavior problems. Our results suggest that CU behaviors and fear recognition have a partly shared genetic aetiology. This provides support for poor fear recognition as a key neurocognitive endophenotype for CU behaviors. Future research should test a hypothesized causal chain from specific genes, through amygdala functioning and fear recognition, to CU behaviors, and identify specific environmental factors (including intervention) that may disrupt this chain. [ABSTRACT FROM AUTHOR]

Abstract: Using a genetically informed design, this study examined whether children's leadership behavior varied as a function of their reciprocal friends’ behavioral characteristics. Specifically, we tested (a) whether friends’ use of a dual strategy (specifically, indirect aggression with prosocial behavior) was associated with children's leadership behavior and (b) whether, in line with a gene‐environment interaction (GxE), the predictive association between friends’ behaviors and children's leadership behavior varied depending on the child's genetic likelihood for leadership. The sample comprised 239 Monozygotic and same‐sex Dizygotic twin pairs (50% boys) assessed in grade 4 (mean age = 10.4 years, SD = 0.26). Reciprocal friendship and children's and their friends’ prosocial, indirectly aggressive, and physically aggressive behaviors were measured via peer nominations. Children's and friends’ leadership was measured through teacher ratings. Multilevel regression analyses revealed that children's genetic likelihood for leadership was positively associated with their leadership behavior. Moreover, the higher their genetic likelihood for leadership, the more children displayed increased leadership behavior when friends showed a combination of indirect aggression and prosocial behavior (GxE). These results underline the role of friends’ behaviors in explaining children's leadership. Socializing with bistrategic friends seems to foster leadership skills especially in children with a genetic likelihood for leadership. [ABSTRACT FROM AUTHOR]

Poverty is a well-established risk factor for behavior problems, yet our understanding of putative family mediators during early childhood (i.e., before age 5 years) is limited. The present study investigated whether the association between poverty and behavior problems during early childhood is mediated simultaneously by perceived parenting, family dysfunction and/or maternal depression symptoms. Outcomes measures were high trajectories of physical aggression and hyperactivity between 1.5 and 5 years. Poverty was defined as living 2-4 years below the low-income thresholds defined by Statistics Canada. Using data from the first five rounds of the Quebec Longitudinal Study of Child Development, logistic regressions models showed that poverty was associated with a higher likelihood of being assigned to the high trajectory of physical aggression and hyperactivity. Overprotection and maternal depression symptoms mediated observed associations. Interventions targeting maternal depression, parenting, and poverty should help reducing children's risk for early behavior problems. [ABSTRACT FROM AUTHOR]

Food insecurity (which can be defined as inadequate access to sufficient, safe, and nutritious food that meets individuals' dietary needs) is concurrently associated with children's psychological difficulties. However, the predictive role of food insecurity with regard to specific types of children's mental health symptoms has not previously been studied. We used data from the Longitudinal Study of Child Development in Québec, LSCDQ, a representative birth cohort study of children born in the Québec region, in Canada, in 1997-1998 (n = 2120). Family food insecurity was ascertained when children were 1K and 4K years old. Children's mental health symptoms were assessed longitudinally using validated measures of behaviour at ages 4K, 5, 6 and 8 years. Symptom trajectory groups were estimated to identify children with persistently high levels of depression/anxiety (21.0%), aggression (26.2%), and hyperactivity/inattention (6.0%). The prevalence of food insecurity in the study was 5.9%. In sex-adjusted analyses, children from food-insecure families were disproportionately likely to experience persistent symptoms of depression/anxiety (OR: 1.79, 95% CI 1.15-2.79) and hyperactivity/inattention (OR: 3.06, 95% CI 1.68-5.55). After controlling for immigrant status, family structure, maternal age at child's birth, family income, maternal and paternal education, prenatal tobacco exposure, maternal and paternal depression and negative parenting, only persistent hyperactivity/inattention remained associated with food insecurity (fully adjusted OR: 2.65, 95% CI 1.16- 6.06). Family food insecurity predicts high levels of children's mental health symptoms, particularly hyperactivity/ inattention. Addressing food insecurity and associated problems in families could help reduce the burden of mental health problems in children and reduce social inequalities in development. [ABSTRACT FROM AUTHOR]

This study explored whether early elementary school aged children's externalizing problems impede academic functioning and foster negative social experiences such as peer victimization, thereby making these children vulnerable for developing internalizing problems and possibly increasing their externalizing problems. It also explored whether early internalizing problems contributed to an increase in externalizing problems. The study examined 1,558 Canadian children from ages 6 to 8 years. Externalizing and internalizing problems, peer victimization, and school achievement were assessed annually. Externalizing problems lead to academic underachievement and experiences of peer victimization. Academic underachievement and peer victimization, in turn, predicted increases in internalizing problems and in externalizing problems. These pathways applied equally to boys and girls. No links from internalizing to externalizing problems were found. [ABSTRACT FROM AUTHOR]

Researchers know relatively little about the normative development of children's behaviors aimed at alleviating distress or discomfort in others. In this article, the authors aim to describe the continuity and discontinuity in the degree to which young children in the general population are reported to exhibit specific prosocial behaviors. Data came from the Quebec Longitudinal Study of Child Development. Consistent with Hay's model of prosocial development, the results show that there were about as many children who stopped exhibiting prosocial behaviors between 29 and 41 months of age as there were children who started doing so during this period. Further, gender differences (girls > boys) in prosocial behaviors are either emerging or at least increasing in magnitude, with girls being more likely to start and boys being more likely to stop exhibiting these behaviors between 29 and 41 months of age. Consistent with the early-onset hypothesis, children who exhibit prosocial behaviors at 17 months of age are less likely to stop exhibiting the same behaviors between 29 and 41 months of age. Otherwise, if they did not exhibit prosocial behaviors at 29 months of age, they are also more likely to start doing so in the following year. [ABSTRACT FROM AUTHOR]

We report the heritability of response inhibition, latency, and variability, which are potential markers of genetic risk in neuropsychiatric conditions. Genetic and environmental influences on cancellation and restraint, response latency, and variability measured in a novel variant of the stop signal task were studied in 139 eight-year-old twin pairs from a birth cohort. Cancellation (50%), restraint (27%), and response latency (41%) showed significant heritability, the balance being non-shared environmental influences and/or error. Response variability was not heritable, with 23% of the variance attributable to shared environmental influences and 77% to non-shared environmental risk or error. The phenotypic correlation between response cancellation and restraint was −.44 and between response latency and restraint was .21. These phenotypic correlations were entirely genetic in origin. The phenotypic correlation between response variability and % successful inhibition was .27, but was not genetic. Cancellation and restraint were heritable and shared genetic influences, indicating that they may be influenced by a common gene or genes. Response latency was moderately heritable and shared genetic influences with restraint, but was not correlated with cancellation. Response variability was not heritable. These results support the potential of response inhibition and latency as endophenotypes in genetic research. (JINS, 2011, 17, 238–247) [ABSTRACT FROM AUTHOR]

The present study examined the association between theory of mind and indirect versus physical aggression, as well as the potential moderating role of prosocial behavior in this context. Participants were 399 twins and singletons drawn from two longitudinal studies in Canada. At five years of age, children completed a theory of mind task and a receptive vocabulary task. A year later, teachers evaluated children's indirect and physical aggression and prosocial behavior. Indirect aggression was significantly and positively associated with theory of mind skills, but only in children with average or low levels of prosocial behavior. Physical aggression was negatively associated with prosocial behavior but not with theory of mind. Each analysis included gender, receptive vocabulary, and the respective other subtype of aggression as control variables. These results did not differ between girls and boys or between twins and singletons. Theoretical and clinical implications of these findings are discussed. [ABSTRACT FROM AUTHOR]

This study investigated the understanding of false belief and emotion in monozygotic (MZ) and same-sex dizygotic (DZ) twin pairs compared to non-twin children. Aged 3;9 to 5;1 years, the children (N=123) were administered three false belief and three emotion understanding tasks. Age, family socioeconomic status, mother's level of education and language abilities were controlled. Results showed no difference between the three groups in false belief understanding. On emotion tasks, non-twin children and DZ twins did not differ from each other, but they both performed better than MZ twins. Results are discussed in terms of the Peterson's (2000) variety hypothesis and suggest that the affective closeness experienced by MZ twins might interfere with their understanding of others' emotions. [ABSTRACT FROM AUTHOR]

This study investigated associations between maternal prenatal smoking and physical aggression (PA), hyperactivity-impulsivity (HI) and co-occurring PA and HI between ages 17 and 42 months in a population sample of children born in Québec (Canada) in 1997/1998 (N=1745). Trajectory model estimation showed three distinct developmental patterns for PA and four for HI. Multinomial regression analyses showed that prenatal smoking significantly predicted children's likelihood to follow different PA trajectories beyond the effects of other perinatal factors, parental psychopathology, family functioning and parenting, and socio-economic factors. However, prenatal smoking was not a significant predictor of HI in a model with the same control variables. Further multinomial regression analyses showed that, together with gender, presence of siblings and maternal hostile reactive parenting, prenatal smoking independently predicted co-occurring high PA and high HI compared to low levels of both behaviors, to high PA alone, and to high HI alone. These results show that maternal prenatal smoking predicts multiple behavior regulation problems in early childhood. [ABSTRACT FROM AUTHOR]

Using a genetic design of 234 six-year-old twins, this study examined (a) the contribution of genes and environment to social versus physical aggression, and (b) whether the correlation between social and physical aggression can be explained by similar genetic or environmental factors or by a directional link between the phenotypes. For social aggression, substantial (shared and unique) environmental effects but only weak genetic effects were found. For physical aggression, significant effects of genes and unique environment were found. Bivariate modeling suggests that social and physical aggression share most of their underlying genes but only very few overlapping environmental factors. The correlation between the two phenotypes can also be explained by a directional effect from physical to social aggression. [ABSTRACT FROM AUTHOR]

Objectives. Physical aggression in children is a major public health problem. Not only is childhood physical aggression a precursor of the physical and mental health problems that will be visited on victims, but also aggressive children themselves are at higher risk of alcohol and drug abuse, accidents, violent crimes, depression, suicide attempts, spouse abuse, and neglectful and abusive parenting. Furthermore, violence commonly results in serious injuries to the perpetrators themselves. Although it is unusual for young children to harm seriously the targets of their physical aggression, studies of physical aggression during infancy indicate that by 17 months of age, the large majority of children are physically aggressive toward siblings, peers, and adults. This study aimed, first, to identify the trajectories of physical aggression during early childhood and, second, to identify antecedents of high levels of physical aggression early in life. Such antecedents could help to understand better the developmental origins of violence later in life and to identify targets for preventive interventions. Methods. A random population sample of 572 families with a 5-month-old newborn was recruited. Assessments of physical aggression frequency were obtained from mothers at 17, 30, and 42 months after birth. Using a semiparametric, mixture model, distinct clusters of physical aggression trajectories were identified. Multivariate logit regression analysis was then used to identify which family and child characteristics, before 5 months of age, predict individuals on a high-level physical aggression trajectory from 17 to 42 months after birth. Results. Three trajectories of physical aggression were identified. The first was composed of children who displayed little or no physical aggression. These individuals were estimated to account for ˜28% of the sample. The largest group, estimated at ˜58% of the sample, followed a risking trajectory of modest aggression.... [ABSTRACT FROM AUTHOR]