Concurrent and prospective associations between family socioeconomic status, social support and salivary diurnal and hair cortisol in adolescence.

BACKGROUND: Exposure to socioeconomic adversity is hypothesized to impact hypothalamic-pituitary-adrenal (HPA) axis activity and cortisol secretion, but existing evidence is inconsistent. Yet, few studies have investigated this association using a developmental approach that considers potential protective contextual factors. This study examined the role of stability and changes in family socioeconomic status (SES) in the prediction of multiple cortisol indicators and tested whether social support moderated these associations. METHODS: Participants were part of a population-based sample of twin pairs recruited at birth. Family SES was assessed in early childhood (ages 0-5) and mid-adolescence (age 14). Social support was assessed at ages 14 and 19. Diurnal cortisol (n = 569) was measured at age 14 at awakening, 30 min later, in the afternoon and evening over four non-consecutive days. Hair cortisol concentration (HCC, n = 704) was measured at age 19. All data were collected before the pandemic and multilevel regression models were conducted to account for the nested data structure. RESULTS: Youth exposed to lower family SES levels in childhood and mid-adolescence had a flatter diurnal slope and higher HCC compared with those who experienced upward socioeconomic mobility in mid-adolescence. Contrastingly, mid-adolescence SES showed no association with the diurnal slope or HCC for youth from higher-SES households in early childhood. Moreover, youth raised in higher-SES families in early childhood had a higher CAR in mid-adolescence if they reported greater social support in mid-adolescence. Social support also moderated the SES-cortisol association in mid-adolescence, with higher-SES youth showing higher awakening cortisol secretion when reporting more social support. CONCLUSIONS: Our findings support the hypothesis that early socioeconomic adversity sensitizes HPA axis activity to later socioeconomic disadvantage, which may bear consequences for socioemotional and behavioral functioning.

Childhood behavior problems and adverse economic outcomes: a 30-year population-based study of intergenerational income mobility.

BACKGROUND: The objectives of this study were to (a) assess the associations between early behavioral problems and intergenerational income mobility (i.e., the degree to which income status is transmitted from one generation to the next), (b) verify whether these associations are moderated by child sex, and (c) explore indirect effects of early behavioral problems on income mobility via high school graduation. METHODS: Data were drawn from the Quebec Longitudinal Study of Kindergarten Children (n = 3,020; 49.17% girls). Participants were followed from age 6 to 37 years. Measures included parents' and teachers' ratings of behavioral problems at age 6 years as well as participants' (ages 30-35 years) and their parents' (when participants were aged 10-19 years) income data obtained from tax return records. Regression models were used to predict upward and downward mobility (i.e., increased or decreased income status from one generation to the next) from attention-deficit/hyperactivity problems, conduct/opposition problems, depression/anxiety problems, prosociality, and the quality of children's relationship with their caregiver. Two-way interaction effects between behavioral problems and child sex were examined and indirect effect models including high school graduation as a mediator of these associations were conducted. RESULTS: Despite their higher educational attainment, females had lower incomes and experienced lower upward (but higher downward) income mobility than males. For both females and males, higher levels of attention-deficit/hyperactivity and conduct/opposition problems were associated with decreased odds of upward mobility, whereas higher levels of attention-deficit/hyperactivity were associated with increased odds of downward mobility. Attention-deficit/hyperactivity problems, conduct/opposition problems as well as low prosociality were associated with lower educational attainment (no high school diploma), which in turn was associated with increased odds of downward mobility. CONCLUSIONS: Results highlight the importance of providing intensive support to children with early behavioral problems as a means of improving educational attainment and intergenerational income mobility.

Reconsidering the failure model: Using a genetically controlled design to assess the spread of problems from reactive aggression to internalizing symptoms through peer rejection across the primary school years.

According to the failure model (Patterson & Capaldi, 1990), peer rejection is the intermediary link between problem behaviors and internalizing symptoms. The present study tested the model with 464 monozygotic and same-sex dizygotic twin pairs (234 female, 230 male dyads). Teacher-reported reactive aggression and internalizing symptoms, and peer-reported peer rejection were collected at ages 6, 7, and 10 (from 2001 to 2008). Support for the failure model emerged in conventional non-genetically controlled analyses, but not twin-difference score analyses (which remove shared environmental and genetic contributions). Univariate biometric models attributed minimal variance in failure model variables to shared environmental factors, suggesting that genetic factors play an important unacknowledged role in developmental pathways historically ascribed to nonshared experiences in the failure model.

Mechanisms and pathways linking kindergarten behavior problems with mid-life employment earnings for males from low-income neighborhoods.

Childhood behavior problems are associated with reduced labor market participation and lower earnings in adulthood, but little is known about the pathways and mechanisms that explain these associations. Drawing on a 33-year prospective birth cohort of White males from low-income backgrounds (n = 1040), we conducted a path analysis linking participants' teacher-rated behavior problems at age 6 years-that is, inattention, hyperactivity, aggression-opposition, and low prosociality-to employment earnings at age 35-39 years obtained from tax records. We examined three psychosocial mediators at age 11-12 years (academic, behavioral, social) and two mediators at age 25 years (non-high school graduation, criminal convictions). Our findings support the notion that multiple psychosocial pathways-especially low education attainment-link kindergarten behavior problems to lower employment earnings decades later.

Genetic and phenotypic evidence of the predictive validity of preschool parent reports of hyperactivity/impulsivity and inattention.

To determine the validity of parent reports (PRs) of ADHD in preschoolers, we assessed hyperactivity/impulsivity (HI) and inattention (IN) in 1114 twins with PRs at 1.5, 2.5, 4, 5, 14, 15, and 17 years, and teacher-reports at 6, 7, 9, 10, and 12. We examined if preschool PRs (1) predict high HI/IN trajectories, and (2) capture genetic contributions to HI/IN into adolescence. Group-based trajectory analyses identified three 6-17 years trajectories for both HI and IN, including small groups with high HI (N = 88, 10.4%, 77% boys) and IN (N = 158, 17.3%, 75% boys). Controlling for sex, each unit of HI PRs starting at 1.5 years and at 4 years for IN, increased more than 2-fold the risk of belonging to the high trajectory, with incremental contributions (Odds Ratios = 2.5-4.5) at subsequent ages. Quantitative genetic analyses showed that genetic contributions underlying preschool PRs accounted for up to a quarter and a third of the heritability of later HI and IN, respectively. Genes underlying 1.5-year HI and 4-year IN contributed to 6 of 8 later HI and IN time-points and largely explained the corresponding phenotypic correlations. Results provide phenotypic and genetic evidence that preschool parent reports of HI and IN are valid means to predict developmental risk of ADHD.

Childhood behavioral problems are associated with the intergenerational transmission of low education: a 16-year population-based study.

The intergenerational transmission of low educational attainment is well-documented, but little is known about how behavioral problems in childhood explain this association. Drawing upon a population-based cohort study (n = 3020) linked to administrative records, we investigated the extent to which inattentive, internalizing, externalizing, and prosocial behaviors at child ages 6-8 years accounted for associations between parental education and child's risk of failing to graduate from high school. We adjusted for economic, demographic, cognitive, and perinatal factors, as well as parental mental health. Using logistic regressions and the Karlson-Holm-Breen decomposition method, we found that childhood behaviors together explained 19.5% of the association between mother's education and child's high school graduation status at age 22/23, and 13.7% of the association between father's education and this same outcome. Inattentive behaviors were most strongly associated with failure to graduate from high school, while the role of other behaviors was modest or negligible. Inattentive behaviors may represent a mediational pathway between parental education and child education. Early interventions targeting inattentive behaviors could potentially enhance the prospects of intergenerational educational mobility.

Perinatal and early-life factors associated with stable and unstable trajectories of psychopathic traits across childhood.

BACKGROUND: This study aimed to identify perinatal and early-life factors associated with trajectories of psychopathic traits across childhood. METHODS: Participants were 1631 children (51.5% girls) from the Quebec Longitudinal Study of Child Development. A wide range of perinatal and early-life factors were assessed from pregnancy to age 2.5 years using medical files and mothers' reports. Psychopathic traits were assessed via teachers' reports at ages 6, 7, 8, 10, and 12 years. Latent class growth analyses and multinomial logistic regressions controlling for child sex were conducted. Two-way interaction effects between perinatal/early-life factors and child sex were explored. RESULTS: Four trajectories of psychopathic traits were identified: High-stable (4.48%), Increasing (8.77%), Decreasing (11.46%), and Low-stable (75.29%). A few perinatal factors and most child-level and family-level early-life factors significantly increased the odds of following the High-stable v. the Low-stable trajectory. Higher levels of psychotropic exposures during pregnancy, socioeconomic adversity, child's physical aggression, child's opposition, mother's depressive symptoms, and hostile parenting increased the likelihood of following the Increasing instead of the Low-stable trajectory. Higher socioeconomic adversity, mother's depressive symptoms, and inconsistent parenting were associated with membership to the High-stable instead of the Decreasing trajectory. Most associations were not moderated by child sex. CONCLUSIONS: These results shed light on the perinatal and early-life factors that are associated with specific pathways of psychopathic traits during childhood and suggest that different factors could be targeted to prevent the exacerbation (v. low and stable levels) or the stability at high levels (v. attenuation) of these traits.

Childhood externalizing, internalizing and comorbid problems: distinguishing young adults who think about suicide from those who attempt suicide.

BACKGROUND: While childhood externalizing, internalizing and comorbid problems have been associated with suicidal risk, little is known about their specific associations with suicidal ideation and attempts. We examined associations between childhood externalizing, internalizing and comorbid problems and suicidal ideation (without attempts) and attempts by early adulthood, in males and females. METHOD: Participants were from the Quebec Longitudinal Study of Kindergarten Children, a population-based study of kindergarteners in Quebec from 1986 to 1988 and followed-up until 2005. We captured the co-development of teacher-rated externalizing and internalizing problems at age 6-12 using multitrajectories. Using the Diagnostic Interview Schedule administered at age 15 and 22, we identified individuals (1) who never experienced suicidal ideation/attempts, (2) experienced suicidal ideation but never attempted suicide and (3) attempted suicide. RESULTS: The identified profiles were no/low problems (45%), externalizing (29%), internalizing (11%) and comorbid problems (13%). After adjusting for socioeconomic and familial characteristics, children with externalizing (OR 2.00, CI 1.39-2.88), internalizing (OR 2.34, CI 1.51-3.64) and comorbid (OR 3.29, CI 2.05-5.29) problems were at higher risk of attempting suicide (v. non-suicidal) by age 22 than those with low/no problems. Females with comorbid problems were at higher risk of attempting suicide than females with one problem. Childhood problems were not associated with suicidal ideation. Externalizing (OR 2.01, CI 1.29-3.12) and comorbid problems (OR 2.28, CI 1.29-4.03) distinguished individuals who attempted suicide from those who thought about suicide without attempting. CONCLUSION: Childhood externalizing problems alone or combined with internalizing problems were associated with suicide attempts, but not ideation (without attempts), suggesting that these problems confer a specific risk for suicide attempts.

Mental health comorbidities following peer victimization across childhood and adolescence: a 20-year longitudinal study.

BACKGROUND: Peer victimization is associated with a wide range of mental health problems in youth, yet few studies described its association with mental health comorbidities. METHODS: To test the association between peer victimization timing and intensity and mental health comorbidities, we used data from 1216 participants drawn from the Quebec Longitudinal Study of Child Development, a population-based birth cohort. Peer victimization was self-reported at ages 6-17 years, and modeled as four trajectory groups: low, childhood-limited, moderate adolescence-emerging, and high-chronic. The outcomes were the number and the type of co-occurring self-reported mental health problems at age 20 years. Associations were estimated using negative binomial and multinomial logistic regression models and adjusted for parent, family, and child characteristics using propensity score inverse probability weights. RESULTS: Youth in all peer victimization groups had higher rates of co-occurring mental health problems and higher likelihood of comorbid internalizing-externalizing problems [odds ratios ranged from 2.06, 95% confidence interval (CI) 1.52-2.79 for childhood-limited to 4.34, 95% CI 3.15-5.98 for high-chronic victimization] compared to those in the low victimization group. The strength of these associations was highest for the high-chronic group, followed by moderate adolescence-emerging and childhood-limited groups. All groups also presented higher likelihood of internalizing-only problems relative to the low peer victimization group. CONCLUSIONS: Irrespective of timing and intensity, self-reported peer victimization was associated with mental health comorbidities in young adulthood, with the strongest associations observed for high-chronic peer victimization. Tackling peer victimization, especially when persistent over time, could play a role in reducing severe and complex mental health problems in youth.

Uncovering the genetic architecture of broad antisocial behavior through a genome-wide association study meta-analysis.

Despite the substantial heritability of antisocial behavior (ASB), specific genetic variants robustly associated with the trait have not been identified. The present study by the Broad Antisocial Behavior Consortium (BroadABC) meta-analyzed data from 28 discovery samples (N = 85,359) and five independent replication samples (N = 8058) with genotypic data and broad measures of ASB. We identified the first significant genetic associations with broad ASB, involving common intronic variants in the forkhead box protein P2 (FOXP2) gene (lead SNP rs12536335, p = 6.32 × 10-10). Furthermore, we observed intronic variation in Foxp2 and one of its targets (Cntnap2) distinguishing a mouse model of pathological aggression (BALB/cJ strain) from controls (BALB/cByJ strain). Polygenic risk score (PRS) analyses in independent samples revealed that the genetic risk for ASB was associated with several antisocial outcomes across the lifespan, including diagnosis of conduct disorder, official criminal convictions, and trajectories of antisocial development. We found substantial genetic correlations of ASB with mental health (depression rg = 0.63, insomnia rg = 0.47), physical health (overweight rg = 0.19, waist-to-hip ratio rg = 0.32), smoking (rg = 0.54), cognitive ability (intelligence rg = -0.40), educational attainment (years of schooling rg = -0.46) and reproductive traits (age at first birth rg = -0.58, father's age at death rg = -0.54). Our findings provide a starting point toward identifying critical biosocial risk mechanisms for the development of ASB.

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.

Behaviors in kindergarten are associated with trajectories of long-term welfare receipt: A 30-year population-based study.

This study examines the link between behavior in kindergarten and adult-life welfare receipt. Teacher-rated behavioral assessments were obtained for inattention, hyperactivity, aggression-opposition, anxiety, and prosociality when children (n=2960) were aged 5-6 years and linked to their tax return records from age 18-35 years. We used group-based based trajectory modeling to identify distinct trajectories of welfare receipt and multinomial logistic regression models to examine the association between behaviors and trajectory group membership. The child's sex, IQ, and family background were adjusted for. Four trajectories of welfare receipt were identified: low (n = 2,390, 80.7%), declining (n = 260, 8.8%), rising (n = 150, 5.2%), and chronic (n = 160, 5.4%). Relative to the low trajectory, inattention and aggression-opposition at age 6 years were associated with increased risk of following a declining, rising, and chronic trajectory of welfare receipt, independent of hyperactivity and anxiety. Prosocial behaviors were independently associated with a lower risk of following a chronic trajectory. This study shows that kindergarten children exhibiting high inattention and aggression-opposition and low prosocial behaviors may be at increased risk of long-term welfare receipt in adulthood. The implications for early screening, monitoring, and prevention are discussed.

Longitudinal patterns of polysubstance use throughout adolescence: association with adult substance use and psychosocial outcomes controlling for preadolescent risk factors in a male cohort.

PURPOSE: Inconsistent reports raise the question of the extent to which poor adult outcomes are associated with adolescent polysubstance use (PSU: alcohol, marijuana, other illicit drugs) above and beyond earlier risk factors. METHODS: Early adulthood substance-related and psychosocial outcomes were examined in association with age 13 to 17 developmental patterns of PSU in boys from urban, low SES neighborhoods (N = 926). Three classes obtained by latent growth modeling described low/non-users (N = 565, 61.0%), lower risk PSU (later onset, occasional use, 2 ≤ substances; N = 223, 24.1%), and higher risk PSU (earlier onset, frequent use, 3 ≥ substances; N = 138, 14.9%). Preadolescent individual, familial and social predictors of adolescent PSU patterns were used as covariates. RESULTS: Adolescent PSU contributed to both age-24 substance-related outcomes (frequency of alcohol, drug use, and getting drunk, risky behaviors under influence, and use-related problems) and psychosocial outcomes (no high school diploma, professional or financial strain, ASP symptoms, criminal record) over and above preadolescent risk factors. Controlling for preadolescent risk factors, adolescent PSU made a more important contribution to adult substance use outcomes (increasing the risk by about 110%) than to psychosocial outcomes (16.8% risk increase). PSU classes showed poorer adjustment for all age-24 substance use, and for various psychosocial outcomes than low/non-users. Higher risk polysubstance users also reported poorer outcomes than their lower risk peers for most substance use outcomes, and for professional or financial strain and criminal record. CONCLUSION: Findings highlight the contribution of adolescent PSU in a dose-response fashion, over and above preadolescent risk factors, on both homotypic and heterotypic outcomes in early adulthood.

Links between peer victimization, dating violence victimization and depression in adolescence: A genetically-informed study.

OBJECTIVE: The current study aimed to test if individuals with inherent dispositions to depression-related cognitions and behaviors are more at risk of experiencing relational difficulties, such as peer victimization and dating violence victimization. METHOD: This study used a genetically informed design with 806 twins (51.5% girls) to test 1) if at least part of the association between peer victimization in school and dating violence victimization in emerging adulthood can be explained by common underlying heritable factors. Participants provided repeated assessments of their peer victimization in school at ages 13 through 17, their depression symptoms at ages 13 through 19, as well as their victimization in dating relationships at age 19. RESULTS: A Cholesky decomposition based on structural equation modeling supported the hypotheses. Specifically, the association between peer victimization and dating violence victimization was to a significant extent explained by common underlying genetic vulnerabilities that were associated with depression symptoms. No sex moderation was found. CONCLUSIONS: The findings highlight the importance of addressing early indicators of vulnerability toward depression symptoms to prevent victimization by peers or dating partners.

Childhood psychopathic traits and mental health outcomes in adolescence: compensatory and protective effects of positive relationships with parents and teachers.

We identified mental health outcomes associated with specific developmental trajectories of psychopathic traits across childhood and tested whether positive relationships with parents and teachers have compensatory or protective effects. Participants were 1401 children (52.82% girls) from the Quebec Longitudinal Study of Child Development with available data on teacher-reported psychopathic traits (ages 6-12 years) and self-reported mental health outcomes (ages 15-17 years). Parents and teachers reported their levels of positive relationship with the child (ages 6-8 and 10-12 years). Trajectories of psychopathic traits (High-stable, Increasing, Decreasing, and Low-stable) were included as predictors of mental health outcomes (e.g., conduct disorder, anxiety) in structural equation models controlling for child sex, family SES, and earlier psychopathology. Compensatory effects were tested via main effects of positive relationships and protective effects were tested via their interactive effects with trajectories memberships. When compared to the Low-stable trajectory of psychopathic traits, the High-stable, Increasing, and Decreasing trajectories were associated with distinct sets of mental health outcomes, with children from the Increasing trajectory being at higher risk for both externalizing and internalizing psychopathology. Positive relationships with parents and teachers only partially compensated for these effects. Findings suggest that clinicians cannot expect the detrimental effects associated with psychopathic traits to be entirely prevented by children's positive relationships with parents and/or teachers. This study reinforces the importance of providing intensive preventive interventions to elementary school children with high levels of psychopathic traits to prevent the long-term negative consequences associated with these traits.

Developmental Patterns of Gambling Participation and Substance use Throughout Adolescence in a Population Birth Cohort.

This study investigated adolescents' single and co-occurring developmental patterns of gambling participation and substance use and their association with gambling and substance use-related issues at age 17, controlling for confounders. Multiple assessments from age 12 to 17 were conducted in a population-based cohort (N=1594, 51.2% boys). Latent growth modeling was used to analyze developmental patterns and Generalized linear models to examine their association with age-17 gambling and substance use-related problems, types and variety of activities, and substance abuse. Results revealed six developmental patterns, including Low- or Non-substance Users or Gamblers (24.2% sample), two trajectory-classes of Later-Onset Increasing (to a moderate level) substance users, either with or without gambling participation (7.8% and 45.5%, respectively), two trajectory-classes of Early-Onset Increasing (to a higher level) substance users, either with or without gambling participation (6.2% and 12.7%, respectively), and a smaller trajectory-class of Slow-Increasing Substance Users and Early-Onset Gamblers, declining to non-gambling after age 13 (3.6%). Gambling participation and substance use did not appear to influence each other with regard to their onset and course throughout adolescence, and to age-17 types and variety of gambling activities or substances used, problems related to gambling participation or substance use, or substance abuse. These findings are consistent with the addictive syndrome model and with both common and individualized approaches to prevention and treatment for adolescent gamblers or substance users.

Link Between Peer Victimization in College and Cortisol Secretion: Roles of Genetic Vulnerabilities and Social Support.

It is unclear whether peer victimization in college interacts with genetic vulnerabilities or social support in predicting cortisol secretion. This issue was addressed using a sample of 162 Monozygotic and 237 Dizygotic twin pairs (54% females; 86% Whites, 6% Blacks, 6% Asians, 0.3% Native North Americans). At age 19, participants provided hair for cortisol extraction and reported about victimization in college and support by the mother, father, and best friend. Biometric modeling revealed that environmental influences on cortisol secretion were reduced and genetic influences exacerbated when victimization was high. Moderate to high maternal support mitigated the association between victimization and high cortisol secretion. The findings suggest that victimization in college contributes to physical "wear-and-tear", which may be counteracted by social support.

Childhood Overeating and Disordered Eating From Early Adolescence to Young Adulthood: A Longitudinal Study on the Mediating Role of BMI, Victimization and Desire for Thinness.

Eating disorders have early origins, and there could be a continuum between childhood eating behaviors, such as overeating, and long-term disordered eating, but this remains to be shown. BMI, desire for thinness and peer victimization could influence this continuum, but their interactions are unknown. To fill this gap, the study used data from the Quebec Longitudinal Study of Child Development (N = 1511; 52% girls), in which 30.9% of youth presented a trajectory associated with high disordered eating from 12 to 20 years. The results support an indirect association between overeating at age 5 and disordered eating trajectories, with different mediation processes observed between boys and girls. The findings underscore the importance of promoting healthy body images and eating behaviors among youths.

The social and economic impact of the Montreal Longitudinal and Experimental Study.

BACKGROUND: The effectiveness of early prevention programmes and their viability as a public policy option have increasingly caught the attention of scholars and policymakers. Given the implementation costs of such programmes, it is important to assess whether they achieved anticipated objectives and whether they made efficient use of taxpayer money. AIM: To discuss the social and economic impact of a 2-year randomised intervention aimed to improve social skills and self-control (i.e., non-cognitive skills) among disruptive boys from low-income neighbourhoods in Montreal. METHOD: We review findings from published studies documenting the impact of the intervention at different stages of the life course, as well as its cost-effectiveness and cost-benefit. RESULTS: The intervention improved behavioural indicators throughout adolescence and eventually led to greater high school graduation rates, reduced crime, and better labour market outcomes in adulthood. Importantly, the prevention programme generated considerable returns to taxpayer investments. CONCLUSION: Findings from the Montreal Longitudinal Experimental Study have been well-received and have contributed to an early prevention 'awakening' in Quebec and elsewhere.

Changing genetic architecture of body mass index from infancy to early adulthood: an individual based pooled analysis of 25 twin cohorts.

BACKGROUND: Body mass index (BMI) shows strong continuity over childhood and adolescence and high childhood BMI is the strongest predictor of adult obesity. Genetic factors strongly contribute to this continuity, but it is still poorly known how their contribution changes over childhood and adolescence. Thus, we used the genetic twin design to estimate the genetic correlations of BMI from infancy to adulthood and compared them to the genetic correlations of height. METHODS: We pooled individual level data from 25 longitudinal twin cohorts including 38,530 complete twin pairs and having 283,766 longitudinal height and weight measures. The data were analyzed using Cholesky decomposition offering genetic and environmental correlations of BMI and height between all age combinations from 1 to 19 years of age. RESULTS: The genetic correlations of BMI and height were stronger than the trait correlations. For BMI, we found that genetic correlations decreased as the age between the assessments increased, a trend that was especially visible from early to middle childhood. In contrast, for height, the genetic correlations were strong between all ages. Age-to-age correlations between environmental factors shared by co-twins were found for BMI in early childhood but disappeared altogether by middle childhood. For height, shared environmental correlations persisted from infancy to adulthood. CONCLUSIONS: Our results suggest that the genes affecting BMI change over childhood and adolescence leading to decreasing age-to-age genetic correlations. This change is especially visible from early to middle childhood indicating that new genetic factors start to affect BMI in middle childhood. Identifying mediating pathways of these genetic factors can open possibilities for interventions, especially for those children with high genetic predisposition to adult obesity.