Body mass index across development and adolescent hair cortisol: the role of persistence, variability, and timing of exposure.

BACKGROUND: Research suggests a putative role of the glucocorticoid stress hormone cortisol in the accumulation of adiposity. However, obesity and weight fluctuations may also wear and tear physiological systems promoting adaptation, affecting cortisol secretion. This possibility remains scarcely investigated in longitudinal research. This study tests whether trajectories of body mass index (BMI) across the first 15 years of life are associated with hair cortisol concentration (HCC) measured two years later and whether variability in BMI and timing matter. METHODS: BMI (kg/m2) was prospectively measured at twelve occasions between age 5 months and 15 years. Hair was sampled at age 17 in 565 participants. Sex, family socioeconomic status, and BMI measured concurrently to HCC were considered as control variables. RESULTS: Latent class analyses identified three BMI trajectories: "low-stable" (59.2%, n = 946), "moderate" (32.6%, n = 507), and "high-rising" (8.2%, n = 128). BMI variability was computed by dividing the standard deviation of an individual's BMI measurements by the mean of these measurements. Findings revealed linear effects, such that higher HCC was noted for participants with moderate BMI trajectories in comparison to low-stable youth (ß = 0.10, p = 0.03, 95% confidence interval (CI) = [0.02-0.40]); however, this association was not detected in the high-rising BMI youth (ß = -0.02, p = 0.71, 95% CI = [-0.47-0.32]). Higher BMI variability across development predicted higher cortisol (ß = 0.17, p = 0.003, 95% CI = [0.10-4.91]), additively to the contribution of BMI trajectories. BMI variability in childhood was responsible for that finding, possibly suggesting a timing effect. CONCLUSIONS: This study strengthens empirical support for BMI-HCC association and suggests that more attention should be devoted to BMI fluctuations in addition to persistent trajectories of BMI.

Adolescents and Social Media: Longitudinal Links Between Motivations for Using Social Media and Subsequent Internalizing Symptoms.

Knowledge is lacking on whether adolescents' motivations for social media use predict internalizing symptoms, and few studies have considered the moderating role of extraversion. In 2017 (T1) and 2018 (T2), 197 adolescents (49.70% girls, Mage = 13.15, SD = 0.36) from a large metropolitan area participated in this study. Adolescents reported on their social media use motivations and extraversion (at T1) and depressive and anxiety symptoms (T1 and T2). Latent class analysis revealed four motivation profiles at T1: (1) entertainment and fun (30.97%); (2) avoidance and escapism (14.21%); (3) meeting new people, feel involved (16.75%); (4) boredom (38.07%). Social motivations (profile 3) predicted elevated internalizing symptoms at T2. Avoidance and boredom motivations (profile 2 and 4) predicted internalizing symptoms for adolescents with low extraversion. Social media use motivations and extraversion distinguish adolescents who benefit from social media from those who experience difficulties.

Differential Association of Preadolescent Risk Factors Across Developmental Patterns of Adolescent Concurrent Gambling Participation and Substance Use.

Early risk factors for gambling participation (GP) and substance use (SU) in adolescents have usually been studied separately, although these disorders were integrated into the same clinical category over a decade ago. This exploratory study aimed to investigate the early individual, parental, familial and social risk factors associated with developmental patterns of adolescent GP and SU in a population-representative cohort (N = 1594, 51.2% boys). Using a person-centered strategy and multiple assessments from age 12 to 17, six developmental patterns describing joint GP and SU courses were revealed. Non-substance users/non-gamblers served as the reference class in an integrated longitudinal-multivariate analysis framework examining 15 distinct risk factors. Results showed that a core of risk factors were common to all trajectory-classes of substance users with or without GP. For a similar level of SU, most of the risk factors associated with non-gambling users also affected their gambling peers. However, additional risk factors were specifically related to GP. Thus, substance users who also gamble were affected by a greater number of risk factors than non-gambling substance users. Findings are consistent with a developmental syndrome of addiction, which posits a shared etiology between different expressions of addiction as well as differences in risk factors that lead to distinct trajectories of addictive behaviors. They highlight the importance of considering both GP and SU for a comprehensive assessment of adolescents' level of risk with regard to addictive behaviors.

The Social Failure Model: Do Classroom Norms Play a Role in the Development of Antisocial Behavior and Depressive Symptoms?

This study examined the moderating role of descriptive and status norms in the stability of youth's antisocial behavior, and the link between initial antisocial behavior and the development of depressive symptoms over the course of one academic year, while controlling for initial depression levels. A total of 1081 students (51.06% girls; grades 4 through 6) in schools in low to average socio-economic status neighborhoods completed self-reports and a peer nomination inventory in the fall (T1) and spring (T2) of one year. Descriptive norms were operationalized as the classroom- and sex-specific mean level of antisocial behavior. Status norms were operationalized as the classroom- and sex-specific correlation between antisocial behavior and social preference. Descriptive norms moderated the link between T1 and T2 antisocial behavior, such that youth exhibiting high levels of antisocial behavior showed a greater increase in antisocial behavior in classrooms where descriptive norms strongly favored such behavior (i.e., + 1 SD) than in classrooms with neutral or weak descriptive norms (i.e., - 1 SD). Status norms moderated the association between T1 antisocial behavior and T2 depressive symptoms, such that youth with high levels of antisocial behavior had higher depressive symptoms in classrooms where status norms disfavored antisocial behavior than in classrooms with neutral or favorable norms. No moderating effects of sex or grade were observed. These results suggest that both descriptive norms and status norms play important, albeit distinct, roles in exacerbating youth's depressive symptoms and antisocial behavior, but they may also mitigate these same outcomes in favorable contexts.

Are Children Following High Trajectories of Disruptive Behaviors in Early Childhood More or Less Likely to Follow Concurrent High Trajectories of Internalizing Problems?

The developmental association between disruptive behaviors (DBs: hyperactivity-impulsivity, non-compliance, physical aggression) and internalizing problems in early childhood is not well understood and has generated competing hypotheses and mixed results. Using a person-centered strategy, the present study aimed to examine concurrent trajectories of DBs and trajectories of internalizing problems from age 1.5 to 5 years in a population-representative sample (N = 2057; 50.7% boys). Six trajectories of DBs and three trajectories of internalizing problems, based on parent reports and obtained via latent growth modeling across five periods of assessment, were used as longitudinal indicators of each type of behaviors. Children following low or moderate trajectories served as the reference class. Compared to children in the reference class, those in trajectory classes characterized by high levels of co-occurring DBs (OR = 6.60) and, to a lesser extent, those in single high DB classes (OR = 2.78) were more likely to follow a high trajectory of internalizing problems simultaneously. These results support a multiple problem hypothesis regarding the association between DBs and internalizing problems, consistent with a developmental perspective that includes a general factor underpinning different psychopathologies. These findings highlight the importance of considering the co-occurrence between DBs and internalizing problems when studying either construct in children.

Association between developmental patterns of single and concurrent externalizing behaviors and internalizing problems over the preschool years.

The present study investigated whether distinct developmental patterns of externalizing behaviors (EBs: hyperactivity-impulsivity, noncompliance, physical aggression) based on parent reports were repeatedly and differentially associated with separate dimensions of internalizing problems such as general anxiety, separation anxiety, and depressive symptoms across the early, middle, and late preschool years in a population birth cohort (N = 2,057, 50.7% boys). Six high trajectory classes obtained by latent growth modeling were used as longitudinal indicators of single EB and co-occurrent EBs. Children following low or moderate trajectories for all EBs served as the reference class. Results revealed that children in trajectory classes reflecting high levels of co-occurring EBs showed higher levels of general anxiety, separation anxiety, and depressive symptoms across the preschool years. In contrast, children in trajectory classes reflecting single EB manifested higher levels of some, but not all, dimensions of internalizing problems. In addition, their scores varied from one period to another. No sex differences were observed in the above associations. These results underline the need for comprehensive assessments across distinct types of EBs and internalizing problems to better reflect the characteristics that distinguish individual children. Finally, results suggest that children showing early co-occurrent EBs and internalizing symptoms may be an important group to target for in-depth assessment and possibly preventive intervention. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Intergenerational transmission of genetic risk for hyperactivity and inattention. Direct genetic transmission or genetic nurture?

Background: Hyperactivity and inattention, the symptoms of ADHD, are marked by high levels of heritability and intergenerational transmission. Two distinct pathways of genetic intergenerational transmission are distinguished: direct genetic transmission when parental genetic variants are passed to the child's genome and genetic nurture when the parental genetic background contributes to the child's outcomes through rearing environment. This study assessed genetic contributions to hyperactivity and inattention in childhood through these transmission pathways. Methods: The sample included 415 families from the Quebec Newborn Twin Study. Twins' hyperactivity and inattention were assessed in early childhood by parents and in primary school by teachers. The polygenic scores for ADHD (ADHD-PGS) and educational attainment (EA-PGS) were computed from twins' and parents' genotypes. A model of intergenerational transmission was developed to estimate (1) the contributions of parents' and children's PGS to the twins' ADHD symptoms and (2) whether these variances were explained by genetic transmission and/or genetic nurture. Results: ADHD-PGS explained up to 1.6% of the variance of hyperactivity and inattention in early childhood and primary school. EA-PGS predicted ADHD symptoms at both ages, explaining up to 1.6% of the variance in early childhood and up to 5.5% in primary school. Genetic transmission was the only significant transmission pathway of both PGS. The genetic nurture channeled through EA-PGS explained up to 3.2% of the variance of inattention in primary school but this association was non-significant. Conclusions: Genetic propensities to ADHD and education predicted ADHD symptoms in childhood, especially in primary school. Its intergenerational transmission was driven primarily by genetic variants passed to the child, rather than by environmentally mediated parental genetic effects. The model developed in this study can be leveraged in future research to investigate genetic transmission and genetic nurture while accounting for parental assortative mating.

Hair steroid before and after COVID-19 in preschoolers: the moderation of family characteristics.

BACKGROUND: Frequent or prolonged exposure to stressors may jeopardize young children's health. The onset of the COVID-19 pandemic, coupled with disruptions in daily routines and social isolation resulting from public health preventive measures, have raised concerns about its potential impact on children' experienced stress, particularly for young children and vulnerable families. However, whether the pandemic was accompanied by changes in physiological stress remains unknown as perceived stress is not a good proxy of physiological stress. This study examined if preschoolers showed increasing hair steroid concentrations following the onset of the COVID-19 pandemic and whether family characteristics may have exacerbated or buffered these changes. METHODS: 136 preschoolers (2-4 years) provided hair for steroid measurement (cortisol, dehydroepiandrosterone (DHEA), cortisone, cortisol-to-DHEA ratio, cortisol-to-cortisone ratio) in October-November 2019 (T0) and in July-August 2020 (T1). A 2-centimeter hair segment was analyzed, reflecting steroid production over the two months leading up to collection. Family income, conflict resolution and lack of cohesion, as well as parents' COVID-19 stress were reported by parents. Linear mixed models for repeated measures and Bayes factors were used. RESULTS: No significant changes were noted from before to after the onset of the COVID-19 pandemic for most hair steroids. However, a moderating role of family conflict resolution was noted. Children living with parents with a better ability to resolve conflicts had lower levels of DHEA compared to those who had more difficulty managing conflicts. Additionally, lower levels of family cohesion and income were linked to some steroids, especially DHEA, suggesting that these factors may relate to children's physiological stress. Finally, boys had higher DHEA levels than girls. CONCLUSION: Our findings suggest that stress biomarkers were comparable from before to during the COVID-19 pandemic. This observation holds true despite the pandemic being perceived by many as a novel, unpredictable, and potentially threatening event. Findings further suggest that family characteristics are associated with hair steroid, especially DHEA, which deserves further investigation.

Targeting Peer Contagion Dynamics in Children with ADHD: Effects from a Two-Site Randomized Controlled Trial.

OBJECTIVE: Parental Friendship Coaching (PFC) teaches parents to coach their children in friendship skills. This paper examines whether PFC fosters positive peer contagion processes (i.e. dyadic mutuality) and reduces negative peer contagion processes (i.e. coercive joining) within the friendships of children with attention-deficit/hyperactivity disorder (ADHD). METHOD: Participants were 134 families of children with ADHD and peer problems (age 6-11 years; 69% male; 72% white) at two Canadian sites, randomized to PFC or CARE (an active comparison intervention). Children were observed in the lab at baseline, post-treatment, and at 8-month follow-up during cooperation and competition tasks with a real-life friend. Amount and reciprocity of dyadic mutuality indicators (i.e. positive affect and positive behaviors) and coercive joining indicators (i.e. aggressive, controlling, and rule-breaking behaviors) between friends were coded. RESULTS: Across treatment conditions, children showed an increase in the amount of dyadic mutuality during cooperation and a decrease in the amount of coercive joining during competition over time. Relative to CARE, PFC induced a reduced amount of coercive joining behaviors during cooperation at post-treatment and follow-up. However, PFC led to decreases in the reciprocity of positive affect during cooperation at post-treatment and to increases in the reciprocity of coercive joining during competition at follow-up relative to CARE. Moderation analyses suggest PFC was associated with better outcomes for children with externalizing comorbidity, and for those with a stable or a best friend. CONCLUSIONS: Findings highlight the importance of transactional processes, contextual differences, externalizing comorbidities, and friendship status when assessing the efficacy of PFC.

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.

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.

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.

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.

Adolescents and Social Media: Longitudinal Links Between Types of Use, Problematic Use and Internalizing Symptoms.

Studies examining the associations between adolescent social media use and depression/anxiety symptoms show inconsistent results and do not elucidate the direction of associations. Differences in how studies operationalize social media use and consider potential moderating effects of sex and extraversion could contribute to inconsistencies. A distinction has been made between three types of social media use: passive, active and problematic. This study examined longitudinal associations between these types of adolescents' social media use and depression/anxiety symptoms and moderation effects of sex or extraversion. At ages 13 (T1) and 14 (T2), 257 adolescents completed an online questionnaire regarding their depression and anxiety symptoms and problematic social media use as well as three social media use diaries. Cross-lagged panel modeling (CLPM) revealed a positive association between problematic use and later anxiety symptoms (ß = .16, p = .010). Extraversion moderated the association between active use and anxiety (ß = -.14, p = .032). Specifically, active use predicted higher subsequent anxiety symptoms only in adolescents with low to moderate levels of extraversion. No sex moderation was found. While social media use (active or problematic) predicted later anxiety symptoms (but not depression), the reverse was not the case. However, highly extraverted individuals seem to be less vulnerable to potential negative effects of social media use.

Adolescent anxiety and pain problems: A joint, genome-wide investigation and pathway-based analysis.

Both common pain and anxiety problems are widespread, debilitating and often begin in childhood-adolescence. Twin studies indicate that this co-occurrence is likely due to shared elements of risk, rather than reciprocal causation. A joint genome-wide investigation and pathway/network-based analysis of adolescent anxiety and pain problems can identify genetic pathways that subserve shared etiopathogenetic mechanisms. Pathway-based analyses were performed in the independent samples of: The Quebec Newborn Twin Study (QNTS; 246 twin pairs and 321 parents), the Longitudinal Study of Child Development in Quebec (QLSCD; n = 754), and in the combined QNTS and QLSCD sample. Multiple suggestive associations (p<1×10-5), and several enriched pathways were found after FDR correction for both phenotypes in the QNTS; many nominally-significant enriched pathways overlapped between pain problems and anxiety symptoms (uncorrected p<0.05) and yielded results consistent with previous studies of pain or anxiety. The QLSCD and the combined QNTS and QLSCD sample yielded similar findings. We replicated an association between the pathway involved in the regulation of myotube differentiation (GO:0010830) and both pain and anxiety problems in the QLSDC and the combined QNTS and QLSCD sample. Although limited by sample size and thus power, these data provide an initial support to conjoint molecular investigations of adolescent pain and anxiety problems. Understanding the etiology underlying pain and anxiety co-occurrence in this age range is relevant to address the nature of comorbidity and its developmental pathways, and shape intervention. The replication across samples implies that these effects are reliable and possess external validity.

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.

Adolescents' internalizing symptoms predict dating violence victimization and perpetration 2 years later.

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.

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.

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.

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.