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The aim of this longitudinal study was to examine bidirectional associations of adolescents’ internalizing symptoms with dating violence victimization and perpetration. We conducted secondary analyses of the Québec Longitudinal Study of Child Development data (n = 974). Each adolescent completed items from the Conflict Tactics Scale (at ages 15 and 17 years) to assess psychological, physical, and sexual dating violence victimization and perpetration in the past 12 months. Adolescents’ symptoms of depression and general anxiety in the past 12 months were self-reported (at ages 15 and 17 years) using The Mental Health and Social Inadaptation Assessment for Adolescents. There were concurrent associations of adolescents’ internalizing symptoms with dating violence victimization and perpetration. Internalizing symptoms at age 15 years were positively associated with dating violence victimization and perpetration 2 years later in both males and females, even after adjusting for baseline characteristics. However, neither dating violence victimization nor perpetration at age 15 years was associated with internalizing symptoms 2 years later. For males and females, internalizing symptoms put adolescents at risk for future dating violence victimization and perpetration. Interventions that target internalizing symptoms may have the potential to decrease subsequent dating violence.
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.
The COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) project is a large international collaborative effort to analyze individual-level phenotype data from twins in multiple cohorts from different environments. The main objective is to study factors that modify genetic and environmental variation of height, body mass index (BMI, kg/m2) and size at birth, and additionally to address other research questions such as long-term consequences of birth size. The project started in 2013 and is open to all twin projects in the world having height and weight measures on twins with information on zygosity. Thus far, 54 twin projects from 24 countries have provided individual-level data. The CODATwins database includes 489,981 twin individuals (228,635 complete twin pairs). Since many twin cohorts have collected longitudinal data, there is a total of 1,049,785 height and weight observations. For many cohorts, we also have information on birth weight and length, own smoking behavior and own or parental education. We found that the heritability estimates of height and BMI systematically changed from infancy to old age. Remarkably, only minor differences in the heritability estimates were found across cultural–geographic regions, measurement time and birth cohort for height and BMI. In addition to genetic epidemiological studies, we looked at associations of height and BMI with education, birth weight and smoking status. Within-family analyses examined differences within same-sex and opposite-sex dizygotic twins in birth size and later development. The CODATwins project demonstrates the feasibility and value of international collaboration to address gene-by-exposure interactions that require large sample sizes and address the effects of different exposures across time, geographical regions and socioeconomic status.
This study investigated the potential environmental effects of peer victimization and the quality of relationships with parents and friends on diurnal cortisol secretion in mid-adolescence.
This study used the monozygotic (MZ) twin-difference design to control for genetic effects and thus estimate the unique environmental influences on diurnal cortisol. Participants were 136 MZ twin pairs (74 female pairs) for whom cortisol was assessed four times per day over four collection days grouped in a 2-week period in grade 8 (mean age = 14.07 years). Participants also provided self-reports of peer victimization from grade 4 to grade 8 and of the relationship quality with the mother, father and best friend in grade 8.
The expected pattern of diurnal cortisol secretion was observed, with high levels at awakening followed by an increase 30 min later and a progressive decrease subsequently. Controlling for a host of confounders, only within-twin pair differences in peer victimization and a problematic relationship with the mother were significantly linked to twin differences in diurnal cortisol secretion. Specifically, whereas a more problematic mother–child relationship was associated with morning cortisol secretion, peer victimization was linked to cortisol secretion later in the day (diurnal slope).
Controlling for genetic influences and other confounders, stressful relationships with peers and the mother exert unique and time-specific environmental influences on the pattern of diurnal cortisol secretion in mid-adolescence.
We analyzed birth order differences in means and variances of height and body mass index (BMI) in monozygotic (MZ) and dizygotic (DZ) twins from infancy to old age. The data were derived from the international CODATwins database. The total number of height and BMI measures from 0.5 to 79.5 years of age was 397,466. As expected, first-born twins had greater birth weight than second-born twins. With respect to height, first-born twins were slightly taller than second-born twins in childhood. After adjusting the results for birth weight, the birth order differences decreased and were no longer statistically significant. First-born twins had greater BMI than the second-born twins over childhood and adolescence. After adjusting the results for birth weight, birth order was still associated with BMI until 12 years of age. No interaction effect between birth order and zygosity was found. Only limited evidence was found that birth order influenced variances of height or BMI. The results were similar among boys and girls and also in MZ and DZ twins. Overall, the differences in height and BMI between first- and second-born twins were modest even in early childhood, while adjustment for birth weight reduced the birth order differences but did not remove them for BMI.
Physical aggression (PA) tends to have its onset in infancy and to increase rapidly in frequency. Very little is known about the genetic and environmental etiology of PA development during early childhood. We investigated the temporal pattern of genetic and environmental etiology of PA during this crucial developmental period.
Participants were 667 twin pairs, including 254 monozygotic and 413 dizygotic pairs, from the ongoing longitudinal Quebec Newborn Twin Study. Maternal reports of PA were obtained from three waves of data at 20, 32 and 50 months. These reports were analysed using a biometric Cholesky decomposition and linear latent growth curve model.
The best-fitting Cholesky model revealed developmentally dynamic effects, mostly genetic attenuation and innovation. The contribution of genetic factors at 20 months substantially decreased over time, while new genetic effects appeared later on. The linear latent growth curve model revealed a significant moderate increase in PA from 20 to 50 months. Two separate sets of uncorrelated genetic factors accounted for the variation in initial level and growth rate. Non-shared and shared environments had no effect on the stability, initial status and growth rate in PA.
Genetic factors underlie PA frequency and stability during early childhood; they are also responsible for initial status and growth rate in PA. The contribution of shared environment is modest, and perhaps limited, as it appears only at 50 months. Future research should investigate the complex nature of these dynamic genetic factors through genetic–environment correlation (rGE) and interaction (G × E) analyses.
The study examined whether reciprocal friendship quantity or quality can mitigate genetic vulnerability for depression symptoms in children. The sample comprised 168 monozygotic twin pairs and 126 same-sex dizygotic twin pairs assessed in Grade 4 (mean age = 10.04 years). Friendship participation was measured via reciprocal nominations of close friendships within the classroom. Friendship quality was measured through self-reports. Depression symptoms were measured through teacher and peer reports. Genetic vulnerability for depression symptoms was unrelated to friendship participation or the number of reciprocal friends, but it was negatively related to positive friendship quality. In line with gene–environment interaction, genetic risk effects on depression symptoms were mitigated in girls who had at least one close reciprocal friend. In boys, only moderate main effects of genetic vulnerability and friendship participation were found but no interaction between them. However, among boys with at least one reciprocal friend, a greater number of friends was related to fewer depression symptoms whereas no cumulative effect of friendship was found for girls. Finally, positive friendship quality was related to fewer depression symptoms in girls and boys even when controlling for genetic risk. The findings emphasize the importance of teaching social interactional skills that promote high-quality friendship relations to help prevent the development of depression symptoms in children.
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