Childhood maltreatment is a robust predictor of aggression. Research indicates that both maltreatment experiences and aggression are moderately heritable. It has been hypothesized that gene–environment correlation may be at play, whereby genetic predispositions to aggression in parents and children may be confounded with family environments conducive to its expression. Building on this framework, we tested whether maltreatment mediates the association between a polygenic score for aggression (PGSAGG) and school-age aggression, and whether this varied for reactive and proactive aggression.

The sample comprised 721 participants (44.9% males; 99.0% White) with prospective assessments of maltreatment from 5 months to 12 years (10 assessments;1998–2010), and teachers-reported aggression from ages 6 to 13 (6 assessments; 2004–2011). The PGSAGG was derived using a Bayesian estimation method (PRS-CS).

PGSAGG was associated with most aggression measures across specific ages and trajectories. Maltreatment experiences partially mediated the association between PGSAGG and the Childhood-Limited trajectory of reactive – but not proactive – aggression.

Children with higher genetic propensities for aggression were more likely to experience maltreatment, which partly explained the association between PGSAGG and a Childhood-Limited trajectory of reactive aggression during elementary school. This finding reinforces the possibility of confounding influences between genetic liability for aggression and maltreatment experiences.

Childhood irritability and harsh parenting are associated with youth suicide attempts. Parents’ harsh reactions have been associated with children’s irritable behavior. While studies have shown individual associations of irritability and parenting behaviors with suicide risk, few have considered these factors jointly. We aimed to identify profiles of children based on irritability and parenting during childhood and examine their associations with youth suicide attempt.

Participants (N = 1626) were from the Québec Longitudinal Study of Child Development. Mothers reported on childhood irritability, harsh parenting, and positive parenting between ages 3.5 and 8; youth self-reported suicide attempt between ages 13 and 23.

We identified four profiles based on the joint development of irritability and parenting during childhood: (1) low irritability, low harsh parenting, and high positive parenting (30.3%); (2) moderate irritability, moderate harsh parenting, and high positive parenting (28.4%); (3) moderate irritability, moderate harsh parenting, and low positive parenting (26.6%); and (4) high irritability, high harsh parenting, and low positive parenting (14.8%). In logistic regression analyses, only children in the high irritability, high harsh parenting, and low positive parenting profile had higher odds of attempting suicide (OR = 2.51; 95% CI = 1.55–4.09) compared to those in the low irritability, low harsh parenting, and high positive parenting profile. This association remained significant (OR = 1.80; 95% CI = 1.03–3.15) in models adjusting for covariates.

Children with chronically high irritability were also those experiencing the harshest parenting and the least positive parenting, as well as those most at risk of suicide attempt. Targeting both child and parental behavior may maximize suicide prevention efforts among children with high irritability.

To examine how food insecurity in childhood up to adolescence relates to eating habits and weight status in young adulthood.

A longitudinal study design was used to derive trajectories of household food insecurity from age 4·5 to 13 years. Multivariable linear and logistical regression analyses were performed to model associations between being at high risk of food insecurity from age 4·5 to 13 years and both dietary and weight outcomes at age 22 years.

A birth cohort study conducted in the Province of Quebec, Canada.

In total, 698 young adults participating in the Québec Longitudinal Study of Child Development.

After adjusting for sex, maternal education and immigrant status, household income and type of family, being at high risk (compared with low risk) of food insecurity in childhood up to adolescence was associated with consuming higher quantities of sugar-sweetened beverages (ßadj: 0·64; 95 % CI (0·27, 1·00)), non-whole-grain cereal products (ßadj: 0·32; 95 % CI (0·07, 0·56)) and processed meat (ßadj: 0·14; 95 % CI (0·02, 0·25)), with skipping breakfast (ORadj: 1·97; 95 % CI (1·08, 3·53)), with eating meals prepared out of home (ORadj: 3·38; 95 % CI (1·52, 9·02)), with experiencing food insecurity (ORadj: 3·03; 95 % CI (1·91, 4·76)) and with being obese (ORadj: 2·01; 95 % CI (1·12, 3·64)), once reaching young adulthood.

Growing up in families experiencing food insecurity may negatively influence eating habits and weight status later in life. Our findings reinforce the importance of public health policies and programmes tackling poverty and food insecurity, particularly for families with young children.

Peer victimization is associated with a wide range of mental health problems in youth, yet few studies described its association with mental health comorbidities.

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.

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.

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.

This study aimed to identify perinatal and early-life factors associated with trajectories of psychopathic traits across childhood.

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.

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.

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.

Maternal depressive symptoms (MDSs) are negatively associated with children's academic performance, with stronger effects sometimes reported in boys. However, few studies have tested the mechanisms of this association. We examined the mediating role of school engagement and peer victimization in this association and tested for sex differences.

Participants were 1173 families from a population-based longitudinal Canadian study. MDSs were self-reported annually using the Centre for Epidemiologic Studies Depression Scale (child's age: 5 months to 5 years). Data on mediators (peer victimization, cognitive, behavioral, and emotional school engagement) were reported annually from ages 6–10 by multiple informants including children, parents, and teachers using items from validated scales. Mathematics, reading, and writing exam scores at age 12 were obtained from standardized exams administered by Québec's Ministry of Education and Teaching. Structural equation modeling was used to test mediation by school experiences in boys and girls.

Exposure to MDSs was negatively associated with mathematics, reading, and writing scores in girls and with mathematics only in boys. Cognitive and behavioral engagement significantly mediated the association between MDSs and mathematics, reading, and writing scores in girls. There were no significant mediators for boys.

Prevention and intervention strategies aiming to improve school engagement might be beneficial for daughters of mothers experiencing depressive symptoms. Further research is needed to replicate these findings and to identify the mechanisms explaining this association in boys.

We aimed to identify groups of children presenting distinct perinatal adversity profiles and test the association between profiles and later risk of suicide attempt.

Data were from the Québec Longitudinal Study of Child Development (QLSCD, N = 1623), and the Avon Longitudinal Study of Parents and Children (ALSPAC, N = 5734). Exposures to 32 perinatal adversities (e.g. fetal, obstetric, psychosocial, and parental psychopathology) were modeled using latent class analysis, and associations with a self-reported suicide attempt by age 20 were investigated with logistic regression. We investigated to what extent childhood emotional and behavioral problems, victimization, and cognition explained the associations.

In both cohorts, we identified five profiles: No perinatal risk, Poor fetal growth, Socioeconomic adversity, Delivery complications, Parental mental health problems (ALSPAC only). Compared to children with No perinatal risk, children in the Poor fetal growth (pooled estimate QLSCD-ALSPAC, OR 1.89, 95% CI 1.04–3.44), Socioeconomic adversity (pooled-OR 1.42, 95% CI 1.08–1.85), and Parental mental health problems (OR 1.74, 95% CI 1.27–2.40), but not Delivery complications, profiles were more likely to attempt suicide. The proportion of this effect mediated by the putative mediators was larger for the Socioeconomic adversity profile compared to the others.

Perinatal adversities associated with suicide attempt cluster in distinct profiles. Suicide prevention may begin early in life and requires a multidisciplinary approach targeting a constellation of factors from different domains (psychiatric, obstetric, socioeconomic), rather than a single factor, to effectively reduce suicide vulnerability. The way these factors cluster together also determined the pathways leading to a suicide attempt, which can guide decision-making on personalized suicide prevention strategies.

Heritability of antisocial behaviour is estimated at approximately 50% and involves multiple genes.

To investigate the cumulative genetic effects of 116 single nucleotide polymorphisms mapping to 11 candidate serotonergic genes and antisocial behaviours, in adolescence and in early adulthood.

Participants were 410 male members of the Quebec Longitudinal Study of Kindergarten Children, a population-based cohort followed up prospectively from age 6 to age 23. The serotonergic genes were selected based on known physiological processes and prior associations with antisocial behaviours. Antisocial behaviours were self-reported and assessed by using semi-structured interviews in adolescence and in adulthood.

Cumulative, haplotype-based contributions of serotonergic genes conferring risk and protection for antisocial behaviours were detected by using multilocus genetic profile risk scores (MGPRSs) and multilocus genetic profile protection scores (MGPPSs). Cumulatively, haplotype-based MGPRSs and MGPPSs contributed to 9.6, 8.5 and 15.2% of the variance in general delinquency in adolescence, property/violent crimes in early adulthood and physical partner violence in early adulthood, respectively.

This study extends previous research by showing a cumulative effect of multiple haplotypes conferring risk and protection to antisocial behaviours in adolescence and early adulthood. The findings further support the relevance of concomitantly considering multiple serotonergic polymorphisms to better understand the genetic aetiology of antisocial behaviours. Future studies should investigate the interplay between risk and protective haplotype-based multilocus genetic profile scores with the environment.

I.O.-M. holds a Canada Research Chair in the developmental origins of vulnerability and resilience.