A Twin-Singleton Comparison of Developmental Trajectories of Externalizing and Internalizing Problems in 6- to 12-Year-Old Children

Association between twin status with cognitive, behavioral development and brain structure in early adolescence: a retrospective cohort analysis based on the Adolescent Brain Cognitive Development Study

Twin births are related with maternal and fetal adverse outcomes. Little was known about the comparability of the cognitive, behavioral development and brain structure between twins and singletons in early adolescence. This retrospective cohort study was based on data from the United States population-based, prospective, longitudinal observational Adolescent Brain Cognitive Development study. Children with complete twin status information were enrolled, and the exposure variable was twin status. Primary outcomes were cognitive, behavioral development and brain structure in early adolescence. Cognitive and behavioral outcomes were assessed by using the NIH Toolbox and Child Behavioral Checklist, respectively. Brain structure was evaluated by the cortical thickness, area, and volume extracted from the magnetic resonance imaging (MRI) data. Subgroup analyses were conducted by prematurity, birth weight, with sibling, genetic profiles, and twin types (zygosity). From 1st September 2016 to 15th November 2018, 11545 children (9477 singletons and 2068 twins) aged 9-10 years were enrolled. Twins showed mildly lower cognitive performance (|t|> 5.104, P-values < 0.001, False Discovery Rate [FDR] < 0.001), better behavioral outcome (|t|> 2.441, P-values < 0.015, FDR < 0.042), such as lower scores for multiple psychiatric disorders and behavioral issues, and smaller cortical volume (t = - 3.854, P-values < 0.001, FDR < 0.001) and cortical area (t = - 3.872, P-values < 0.001, FDR < 0.001). The observed differences still held when stratified for prematurity, birth weight, presence of siblings, genetic profiles, and twin types (zygosity). Furthermore, analyses on the two-year follow-up data showed consistent results with baseline data. Twin status is associated with lower cognitive and better behavioral development in early adolescence accompanied by altered brain structure. Clinicians should be aware of the possible difference when generalizing results from adolescent twin samples to singletons.

Phenotypic and Genetic Associations Between Preschool Fine Motor Skills and Later Neurodevelopment, Psychopathology, and Educational Achievement

BACKGROUND

Fine motor skills are heritable and comprise important milestones in development, and some evidence suggests that impairments in fine motor skills are associated with neurodevelopmental conditions, psychiatric disorders, and poor educational outcomes.

METHODS

In a preregistered study of 9625 preschool children from TEDS (Twins Early Development Study), fine motor assessments (drawing, block building, folding, and questionnaires) were conducted at 2, 3, and 4 years of age. A cross-age fine motor score was derived using principal component analysis. Multivariate regression analysis was used to examine the relationships between the fine motor score and neurodevelopmental traits, psychopathology, and educational outcomes at 3 later ages (7-8, 12, and 16 years) and cross-age psychopathology composite scores. Polygenic scores (PGSs) were created for attention-deficit/hyperactivity disorder (ADHD), autism, schizophrenia, anxiety, major depressive disorder, obsessive-compulsive disorder, and years of education. We ran single-PGS models and a multi-PGS model.

RESULTS

Fine motor skills were negatively associated with neurodevelopmental traits and psychopathology across childhood and adolescence and positively associated with educational achievement in adolescence (β = 0.25, p < .001). Superior fine motor skills were associated with a higher years-of-education PGS (β = 0.07, p < .001), a lower ADHD PGS (β = -0.04, p = .011), and a higher anxiety PGS (β = 0.03, p = .040). Similarly, the multi-PGS model retained the PGSs for years of education (β = 0.07), ADHD (β = -0.03), and anxiety (β = 0.01). A non-preregistered analysis in an independent preschool sample replicated the ADHD PGS association, but not the years of education or anxiety PGS associations.

CONCLUSIONS

Fine motor skills are linked genetically and phenotypically to later neurodevelopment, psychopathology, and educational outcomes. Future work should investigate the mechanisms that underlie the role of fine motor development in later outcomes.

Demographic and mental health assessments in the adolescent brain and cognitive development study: Updates and age-related trajectories

The Adolescent Brain Cognitive Development (ABCD) Study of 11,880 youth incorporates a comprehensive range of measures assessing predictors and outcomes related to mental health across childhood and adolescence in participating youth, as well as information about family mental health history. We have previously described the logic and content of the mental health assessment battery at Baseline and 1-year follow-up. Here, we describe changes to that battery and issues and clarifications that have emerged, as well as additions to the mental health battery at the 2-, 3-, 4-, and 5-year follow-ups. We capitalize on the recent release of longitudinal data for caregiver and youth report of mental health data to evaluate trajectories of dimensions of psychopathology as a function of demographic factors. For both caregiver and self-reported mental health symptoms, males showed age-related decreases in internalizing and externalizing symptoms, while females showed an increase in internalizing symptoms with age. Multiple indicators of socioeconomic status (caregiver education, family income, financial adversity, neighborhood poverty) accounted for unique variance in both caregiver and youth-reported externalizing and internalizing symptoms. These data highlight the importance of examining developmental trajectories of mental health as a function of key factors such as sex and socioeconomic environment.

Adolescent Big Five personality and pubertal development: Pubertal hormone concentrations and self-reported pubertal status

In early adolescence, levels of conscientiousness and agreeableness have been found to temporarily decrease, with levels of neuroticism increasing, indicating a dip in personality maturation. It is unknown whether these changes are related to the process of puberty, a major developmental milestone with numerous changes for children. Here, we first replicated the dip in personality maturity in early adolescence (N = 2640, age range 8-18, 51% girls, 65% non-Hispanic white, 21% Hispanic/Latino, 10% African American, 9% other, roughly 33% of families received means-tested public assistance) and tested associations between the Big Five personality dimensions and pubertal development and timing across late childhood and adolescence (n = 1793). Pubertal development was measured using both hormonal assays (DHEA, testosterone, and progesterone) and self-reports of secondary sex characteristics. Of hormonal measures, only higher DHEA concentrations were associated with lower conscientiousness and openness. Nonparametric moderation analyses using LOSEM indicated Complex Age × Sex interactions involving all three hormones. Self-reported pubertal development was associated with lower extraversion, conscientiousness, agreeableness, and openness. More advanced pubertal timing was also related to lower levels of extraversion, conscientiousness, and agreeableness. All associations were small. As some evidence was found for small associations between pubertal development and lower levels of conscientiousness and agreeableness, a dip in personality maturation in these personality traits may be partly due to pubertal development in early adolescence. Overall, results did not indicate that pubertal development was the primary explanation of the maturity dip in adolescent personality. Many small influences likely accumulate to explain the dip in personality maturity in early adolescence. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Residential green space and child intelligence and behavior across urban, suburban, and rural areas in Belgium: A longitudinal birth cohort study of twins

BACKGROUND

Exposure to green space has beneficial effects on several cognitive and behavioral aspects. However, to our knowledge, no study addressed intelligence as outcome. We investigated whether the level of urbanicity can modify the association of residential green space with intelligence and behavior in children.

METHODS AND FINDINGS

This study includes 620 children and is part of the East Flanders Prospective Twin Survey (EFPTS), a registry of multiple births in the province of East Flanders, Belgium. Intelligence was assessed with the Wechsler Intelligence Scale for Children-Revised (WISC-R) in 620 children (310 twin pairs) between 7 and 15 years old. From a subset of 442 children, behavior was determined based on the Achenbach Child Behavior Checklist (CBCL). Prenatal and childhood residential addresses were geocoded and used to assign green space indicators. Mixed modeling was performed to investigate green space in association with intelligence and behavior while adjusting for potential confounding factors including sex, age, parental education, neighborhood household income, year of assessment, and zygosity and chorionicity. We found that residential green space in association with both intelligence and behavior in children was modified by the degree of urbanicity (p < 0.001). In children living in an urban environment, multivariable adjusted mixed modeling analysis revealed that an IQR increment of residential green space (3,000-m radius) was associated with a 2.6 points (95% CI 1.4-3.9; p < 0.001) higher total intelligence quotient (IQ) and 2.0 points (95% CI -3.5 to -0.4; p = 0.017) lower externalizing behavioral score. In children residing in a rural or suburban environment, no association was found. A limitation of this study is that no information was available on school location and the potential for unmeasured confounding (e.g., time spend outdoors).

CONCLUSIONS

Our results indicate that residential green space may be beneficial for the intellectual and the behavioral development of children living in urban areas. These findings are relevant for policy makers and urban planners to create an optimal environment for children to develop their full potential.

Is there something special about twin families? A comparison of parenting styles in twin and non-twin families

Twin comparisons offer a powerful quasi-experimental design to study the impact of the family of origin on children's life chances. Yet, there are concerns about the generalizability of results obtained from twin studies because twin families are structurally different and twins have a genetic resemblance. We examine these concerns by comparing mothers' reports on their parenting styles for twin and non-twin children between twin and non-twin families, as well as within twin families. We use two German studies for our comparisons: TwinLife and pairfam. Our results demonstrate that twins receive more differential treatment and more emotional warmth than non-twins; however, these differences are largely accounted for by age differences between children. Overall, our results indicate that results on parenting obtained from twin studies can be generalized to non-twin families.

Ex-Gaussian, Frequency and Reward Analyses Reveal Specificity of Reaction Time Fluctuations to ADHD and Not Autism Traits

Both attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) have been linked to increased reaction time variability (RTV), a marker of attentional fluctuation. Here we test whether specificity to either trait emerges when we examine (1) detailed ex-Gaussian and frequency RTV subcomponents, (2) effects while controlling for the other trait and (3) improvement in the RTV measures following rewards or a faster event rate. 1110 children aged 7-10 years from a population-based sample completed a Go/No-Go task under three conditions (slow, fast and incentives). We measured RTV with standard deviation of RT (SDRT), ex-Gaussian distribution measures (Sigma and Tau), RT fluctuations in cycles of ~14-90 s in all conditions (Slow-4 and Slow-5), and RT fluctuations in cycles of 2-14 s in the fast condition (Slow-2 and Slow-3). Parent-rated ADHD and ASD traits were obtained. All refined RTV components were linked to ADHD traits only and not to ASD traits, while Sigma did not relate to either trait. Although both ADHD and ASD social-communication traits were associated with SDRT, the association with social-communication impairments disappeared when controlling for ADHD traits. A reward-induced improvement in RTV measures, indicating malleability, emerged in relation to ADHD traits but not ASD traits. Under closer inspection, specificity emerges of high RTV to ADHD traits. For the clinician, our findings indicate that attentional fluctuation in children with high ASD traits may be due to co-occurring ADHD traits and emphasise how the effectiveness of rewards does not generalise from ADHD to ASD traits.

Predicting mental health problems in adolescence using machine learning techniques

BACKGROUND

Predicting which children will go on to develop mental health symptoms as adolescents is critical for early intervention and preventing future, severe negative outcomes. Although many aspects of a child's life, personality, and symptoms have been flagged as indicators, there is currently no model created to screen the general population for the risk of developing mental health problems. Additionally, the advent of machine learning techniques represents an exciting way to potentially improve upon the standard prediction modelling technique, logistic regression. Therefore, we aimed to I.) develop a model that can predict mental health problems in mid-adolescence II.) investigate if machine learning techniques (random forest, support vector machines, neural network, and XGBoost) will outperform logistic regression.

METHODS

In 7,638 twins from the Child and Adolescent Twin Study in Sweden we used 474 predictors derived from parental report and register data. The outcome, mental health problems, was determined by the Strengths and Difficulties Questionnaire. Model performance was determined by the area under the receiver operating characteristic curve (AUC).

RESULTS

Although model performance varied somewhat, the confidence interval overlapped for each model indicating non-significant superiority for the random forest model (AUC = 0.739, 95% CI 0.708-0.769), followed closely by support vector machines (AUC = 0.735, 95% CI 0.707-0.764).

CONCLUSION

Ultimately, our top performing model would not be suitable for clinical use, however it lays important groundwork for future models seeking to predict general mental health outcomes. Future studies should make use of parent-rated assessments when possible. Additionally, it may not be necessary for similar studies to forgo logistic regression in favor of other more complex methods.

Parental Conformity Expectations' Effect on Twins' and Singletons' Parent-Adolescent Relationships: Associations With Change in Adjustment From Middle Childhood to Adolescence

Growing use of in vitro fertilization (IVF) has resulted in an elevated twin birth rate, and a burgeoning population of IVF twins who are now aging into adolescence and beyond. This study tests a model examining whether parental conformity expectations have differential effects on twins' versus singletons' parent-adolescent relationship satisfaction, and if this effect is indirectly associated with relative changes in twins' and singletons' internalizing and externalizing behavior from middle childhood to adolescence. Using a sample of 278 IVF twins and singletons, path models demonstrate that twin status and conformity expectations interact to influence parent-adolescent relationships. Although there was an association between twin status and mother-adolescent relationship satisfaction among parents with high conformity expectations (r = .25, p < .01), this relationship was nonsignificant among parents with low conformity expectations (r = .05, p = .85). The differential effect of conformity expectations on parent-adolescent relationship satisfaction for twins and singletons was indirectly associated with relative changes in twins' and singletons' externalizing behavior from middle childhood to adolescence. Results demonstrate that higher levels of parental conformity expectations may not have the same effect on adolescent twins and singletons.

Children's sleep and daytime functioning: Increasing heritability and environmental associations with sibling conflict

Children's sleep has both environmental and genetic influences, with stressful family environmental factors like household chaos and marital conflict associated with sleep duration and quality (El-Sheikh, Buckhalt, Mize, & Acebo, 2006; Fiese, Winter, Sliwinski, & Anbar, 2007). However, it is less clear whether sibling conflict is related to sleep duration and children's sleep problems (e.g., nighttime wakings, parasomnias). In addition, few studies have tested whether associations between sleep and stressful family environmental factors are accounted for by an underlying set of genes or shared and unique environmental factors. Participants were 582 twins with sleep assessed longitudinally at 12, 30 months, and 5 years of age. Sibling conflict was assessed at 5 years. Greater sibling conflict was associated with shorter sleep duration and greater number of total sleep problems, over and above the influence of general household stress and other covariates. The heritability of sleep duration increased with age. Shared environmental factors accounted for the covariance between sibling conflict and sleep duration and total sleep problems. Findings hold promise for interventions, including educating parents about fostering positive sibling relationships and healthy sleep habits.

The Phenomenology of Non-Aggressive Antisocial Behavior During Childhood

Although the phenomenology of overt or aggressive antisocial behavior during childhood is well-documented, far less is known about covert or non-aggressive, rule-breaking (RB) antisocial behavior. Gaps in knowledge include issues as basic as RB's typical symptom presentation during childhood and which symptoms differ across sex. The current study sought to fill these gaps in the literature by establishing the prevalence and psychometric properties of specific RB behaviors in a sample of 1022 twin boys and 1010 twin girls between the ages of 6 and 10 years. Legal RB behaviors (e.g., breaking rules, swears, lying or cheating) were present to varying degrees in most children, regardless of whether or not they passed the clinical threshold for RB. They were also more common in boys than in girls regardless of their clinical status. In sharp contrast, illegal RB behaviors (e.g., stealing, vandalism, setting fires) were rarely observed in typically-developing children, but were seen at moderate levels in boys and girls with clinically-significant levels of RB. Moreover, sex differences in illegal RB behaviors were observed only for those youth with clinically meaningful levels of RB. Such findings collectively imply that while legal RB behaviors can be found (albeit at different frequencies) in children with and without clinically meaningful levels of RB, illegal RB behaviors may function as relatively 'unambiguous' indicator of clinically-significant levels of RB.

Getting Started in Elementary School: Cognitive Competence, Social Skills, Behavior, and Stress

Abstract The entry into elementary education - EE - represents an important transition in child development. The study aimed to assess stability and change in indicators of academic achievement, general intelligence, social skills, behavioral adjustment, and stress between the 1st, 2nd and 3rd year of EE. The participants were 151 children (79 boys), longitudinally evaluated using the Social Skills Rating System, Raven's Progressive Matrices, Provinha Brazil, Child Stress Scale and the School Stressors Inventory. The results indicated at least moderate stability of the variables and a continuous increase in academic achievement. Girls showed better indicators of social skills and behavioral adjustment. Children showed more externalizing behaviors in the 1st year; more stress symptoms in the 2nd year; greater general intelligence, more academic social skills and fewer stress symptoms in the 3rd year. These trends suggest that the transition extends up to 2nd year, whereas developmental achievements are consolidated in the 3rd year.

Efficacy of the Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline in Twin Families (VIPP-Twins): Study protocol for a randomized controlled trial

Background

Intervention programs with the aim of enhancing parenting quality have been found to be differentially effective in decreasing negative child outcomes such as externalizing behavioral problems, resulting in modest overall effect sizes. Here we present the protocol for a randomized controlled trial to examine the efficacy of the Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline for Twin Families (VIPP-Twins) on parenting quality and children’s behavioral control and social competence. In addition, we aim to test the differential susceptibility theory; we examine differential efficacy of the intervention based on genetic make-up or temperament for both parents and children. Lastly, we explore neurobiological mechanisms underlying intervention effects on children’s developmental outcomes.

Methods/design

The original VIPP-SD was adapted for use in families with twins. The VIPP-Twins consists of five biweekly sessions in which the families are visited at home, parent-child interactions are videotaped and parents receive positive feedback on selected video fragments. Families (N = 225) with a same sex twin (mean age = 3.6 years) were recruited to participate in the study. The study consists of four assessments. After two baseline assessments in year 1 and year 2, a random 40 % of the sample will receive the VIPP-Twins program. The first post-test assessment will be carried out one month after the intervention and there will be a long term follow-up assessment two years after the intervention. Measures include observational assessments of parenting and children’s social competence and behavioral control, and neurobiological assessments (i.e., hormonal functioning and neural (re-)activity).

Discussion

Results of the study will provide insights in the efficacy of the VIPP-Twins and reveal moderators and mediators of program efficacy. Overall the randomized controlled trial is an experimental test of the differential susceptibility theory.

Trial registration

Dutch Trial Register: NTR5312; Date registered: July 20, 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s40359-016-0139-y) contains supplementary material, which is available to authorized users.

Impact of asthma medication and familial factors on the association between childhood asthma and attention-deficit/hyperactivity disorder: a combined twin- and register-based study: Epidemiology of Allergic Disease

BACKGROUND

Asthma and attention-deficit/hyperactivity disorder (ADHD) are prevalent in childhood and may cause functional impairment and stress in families. Previous research supports an association between asthma and ADHD in children, but several aspects of this relationship are unclear.

OBJECTIVE

Our aim was to study whether the association between asthma and ADHD is restricted to either the inattentive or the hyperactive/impulsive symptoms of ADHD, to explore the impact of asthma severity and asthma medication and the contribution of shared genetic and environmental risk factors on the asthma-ADHD relationship.

METHODS

Data on asthma, ADHD, zygosity and possible confounders were collected from parental questionnaires at 9 or 12 years on 20 072 twins through the Swedish Twin Register, linked to the Swedish Medical Birth Register, the National Patient Register and the Prescribed Drug Register. The association between asthma and ADHD, the impact of asthma severity and medication, was assessed by generalized estimating equations. Cross-twin-cross-trait correlations (CTCT) were estimated to explore the relative importance of genes and environment for the association.

RESULTS

Asthmatic children had a higher risk of also having ADHD [odds ratio (OR) 1.53, 95% confidence interval (CI): 1.16-2.02]. The association was not restricted to either of the two dimensions of ADHD. The magnitude of the association increased with asthma severity (OR 2.84, 95% CI: 1.86-4.35) for ≥ 4 asthma attacks in the last 12 months and was not affected by asthma treatment. The CTCTs possibly indicate that the genetic component in overlap of the disorders is weak.

CONCLUSIONS AND CLINICAL RELEVANCE

Childhood asthma, especially severe asthma, is associated with ADHD. Asthma medication seems not to increase the risk of ADHD. Clinicians should be aware of the potential of ADHD in asthma. Optimal asthma care needs to be integrated with effective evaluation and treatment of ADHD in children with co-existing disorders.

Men's sexual interest in children: one-year incidence and correlates in a population-based sample of Finnish male twins

In a study of 1,310 Finnish adult male twins we found that sexual interest in children aged 12 or younger was reported by 0.2% of the sample. Sexual interest in children aged 15 or younger was reported by 3.3%. Participants reporting sexual interest in children aged 15 or younger were younger, reported stronger sexual desire, and had experienced more childhood sexual and nonsexual abuse. The present study is the first to give a population-based estimate of the incidence of sexual interest in children among adult men. The 12-month incidence of sexual interest in children below the age of 16 years is roughly comparable to the one-year incidence of major depression or the lifetime prevalence of transvestitic fetishism.

Twins conceived using assisted reproduction: parent mental health, family relationships and child adjustment at middle childhood

STUDY QUESTION

Compared with singletons, what is the parent mental health, parent-child and couple relationship satisfaction, and child adjustment of 6- to 12-year-old assisted reproduction technology (ART) twins and their families?

SUMMARY ANSWER

There are no differences between 6- and 12-year-old ART twin and singleton families in parent mental health or family relationships; however, twins had significantly fewer behavior and attention problems than singletons in middle childhood.

WHAT IS KNOWN ALREADY

When ART twins are younger than 5 years old, parents have more mental health difficulties and poorer parent-child relationship quality, and no differences have been found in ART twin and singletons' psychosocial adjustment. However, studies have only examined the implications of ART twin status in families with infant and toddler aged children.

STUDY DESIGN, SIZE, DURATION

A cross-sectional study of 300 6-12-year-old ART children (n = 124 twins and n = 176 singletons) from 206 families at a reproductive endocrinology clinic in the USA.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Patients from one clinic with a child born between 1998 and 2004 were invited to participate in an online survey (82% recruitment rate). Participants provided information on each 6- to 12-year-old ART child in the family, and responded to questions on parent mental health, family relationships and child adjustment.

MAIN RESULTS AND THE ROLE OF CHANCE

There were no differences in parent mental health or family relationships in families with 6- to 12-year-old ART twins versus singletons. However, twins (M = 2.40, SE = 0.35) had significantly fewer behavior problems than singletons (M = 3.47, SE = 0.36; F(1, 201) = 4.54, b = 1.08, P < 0.05). Twins (M = 1.86, SD = 0.23) also had fewer attention problems than singletons (M = 2.64, SD = 0.23; F(1, 156) = 5.75, b = 0.78, P < 0.05). Results also suggest that full-term twins had significantly fewer attention problems (M = 1.37, SE = 0.33; F(1, 222) = 2.65, P = 0.05) than premature twins (M = 2.32, SE = 0.32, b = 0.95, P < 0.05), full-term singletons (M = 2.25, SE = 0.21, b = 0.88, P < 0.05) and premature singletons (M = 2.84, SE = 0.49, b = 1.47, P = 0.01). There were no significant differences between the other groups.

LIMITATIONS, REASONS FOR CAUTION

Although the response rate is high (82%) and family demographics are representative of US ART patients, patients are from one US clinic. Responses also are from one family member and may be subject to social desirability biases. Additionally, our data did not include identification of monozygotic and dizygotic twins.

WIDER IMPLICATIONS OF THE FINDINGS

Studies on infant and toddler ART twins suggest these families have parents with more mental health difficulties and lower parent-child relationship quality than singleton families. This study indicates the negative effects of twin status may have ameliorated by middle childhood, and twins may even have more optimum psychosocial adjustment than singletons in this developmental period.

STUDY FUNDING/COMPETING INTERESTS

This research is based on a collaborative research effort supported by University of Minnesota Agriculture Experiment Station Project Number MN-52-107, a University of Minnesota Grant-in-Aid of Research, Artistry and Scholarship grant, a University of Minnesota College of Education and Human Development Research Development Investment Grant and the M. Janice Hogan Fellowship. The authors of this article have no commercial or corporate interests to declare.

Sibling bullying and risk of depression, anxiety, and self-harm: a prospective cohort study

OBJECTIVES

Being the victim of peer bullying is associated with increased risk of psychopathology, yet it is not known whether similar experiences of bullying increase risk of psychiatric disorder when the perpetrator is a sibling. We tested whether being bullied by a sibling is prospectively associated with depression, anxiety, and self-harm in early adulthood.

METHODS

We conducted a longitudinal study using data from >6900 participants of a UK community-based birth cohort (Avon Longitudinal Study of Parents and Children) who reported on sibling bullying at 12 years. Our main outcome measures were depression, anxiety, and self-harm, assessed using the Clinical Interview Schedule-Revised during clinic assessments when participants were 18.

RESULTS

Children who were frequently bullied were approximately twice as likely to have depression (odds ratio [OR] = 2.16; 95% confidence interval [CI], 1.33-3.51; P < .001), self-harm (OR = 2.56; 95% CI, 1.63-4.02; P < .001), and anxiety (OR = 1.83; 95% CI, 1.19-2.81; P < .001) as children who were not bullied by siblings. The ORs were only slightly attenuated after adjustment for a range of confounding individual, family, and peer factors. The population-attributable fractions suggested that 13.0% (95% CI, 1.0%-24.7%) of depression and 19.3% (95% CI, 7.6%-29.6%) of self-harm could be explained by being the victim of sibling bullying if these were causal relationships.

CONCLUSIONS

Being bullied by a sibling is a potential risk factor for depression and self-harm in early adulthood. Our results suggest that interventions designed to target sibling bullying should be devised and evaluated.

Do Twins Differ From Single-Born Children on Rates of Behavioral Difficulty in Early Childhood? A Study of Sibling Relationship Risk Factors

The hypothesis that twinning raises risk for behavioral difficulties in childhood is persistent, yet there is limited and inconsistent empirical evidence. Simple mean comparison without control for confounders provides data on prevalence rates but cannot provide knowledge about risk or etiology. To assess the effect of twin relationship on behavior, comparison of patterns of association with single-born siblings may be informative. Analyses of data from an Australian sample of twins and single-born children (N = 305, mean age 4 years 9 months, and a follow-up 12 months later) were undertaken. The outcome measure was the Strengths and Difficulties Questionnaire. Predictor and control measures were obtained from parent report on the sibling/co-twin relationship behavior, family demographics, and obstetric history. We assessed difference between twins and single-born children in two respects: (a) mean behavioral difficulties, and (b) patterns of association between sibling relationship and behavioral difficulties, controlling for confounders. Results showed no differences in mean levels of behavioral difficulties between twins and single-born siblings identifying the importance of statistical control for family and obstetric adversity. Differences in patterns of association were found; for twin children, conflict in their co-twin relationship predicted externalizing behaviors, while for single-born children conflict predicted internalizing behaviors. The findings of mean differences between twin and single-born children in social background, but not in behavioral difficulties, underscore the necessity of statistical control to identify risk associated with twinning compared with risk associated with family and obstetric background factors.

Does low birth weight share common genetic or environmental risk with childhood disruptive disorders?

Although advances in neonatal care over the past century have resulted in increased rates of survival among at-risk births, including infants with low birth weight, we have much to learn about psychological outcomes in this population. In particular, despite growing evidence that low birth weight may be associated with an increased risk for Attention-Deficit/Hyperactive Disorder (ADHD) symptoms in childhood, few studies have examined birth weight as a risk factor for disruptive disorders that commonly co-occur with ADHD. In addition, the etiology of the relation between birth weight and these disorders is unknown. The current investigation aimed to better understand these associations in the context of potentially confounding genetic and environmental influences by examining phenotypic associations between birth weight and disruptive disorder symptoms both between families and within families in two independent twin samples (Sample 1: N = 1,676 individuals; Sample 2: N = 4,038 individuals). We found negative associations between birth weight and inattentive, hyperactive-impulsive, and broad externalizing symptoms in both samples. Nonetheless, the overall magnitude of these associations was very small, contributing to less than 1% of the variance in these symptom dimensions. Within-family associations between birth weight and disruptive disorder symptoms did not differ for monozygotic and dizygotic twin pairs, suggesting that nonshared environmental influences rather than common genetic influences are responsible for these associations. Overall, the consistent albeit weak associations between birth weight and disruptive disorder symptoms suggest that low birth weight may not represent a major risk factor in the development of these symptoms.

Twin and family studies are actually more important than ever

Charney argues that the presence of inherited epigenetic effects makes twin, family, and adoption studies obsolete. This argument relies on both a faulty characterization of these studies and indirect comparisons of DNA and "neogenetic" factors. I argue that twin and family studies will in fact serve a necessary and vital role in the study of epigenetic and neogenetic processes.

Increases in alcohol consumption in women and elderly groups: evidence from an epidemiological study

BACKGROUND

In most Western countries, alcohol consumption continues to increase, specifically among women and older adults. Insight into these trends may aid intervention strategies. Here we present data on alcohol consumption by age and sex as well as associations between alcohol use and demographic lifestyle/traits. The data are from a large (N>16,000) population-based Dutch sample, ascertained based on the presence of twins in the family.

METHODS

A set of 16 indicators of normative and problematic alcohol use was assessed in participants of the Netherlands Twin Register between 2009-2012 (ages 18-97; 6,052 men; 10,535 women). Alcohol consumption and demographic/lifestyle traits, including educational attainment, work-related/financial stress, urbanization, religiousness, smoking/cannabis initiation, and BMI were described by age and sex. Associations were examined by regressing aspects of alcohol use on age, sex, their interaction, and demographic/lifestyle variables.

RESULTS

Age, sex, and initiation of cigarette and cannabis use were the most important predictors of alcohol use. Frequency of alcohol use was lowest between 18-25 years, with 3.2% of men and .6% of women drinking 6-7 times/week, and highest above age 65 years, with 30.6-32.7% of men and 20.2-22.0% of women drinking 6-7 times/week. Women consumed the lowest quantities of alcohol between 25-45 years, with a 5.7-5.9% prevalence of excessive drinking (>14 glasses/week), and the largest quantities between 55-65 years (15.5% excessive drinkers). Age at alcohol initiation, onset of regular drinking, and first alcohol intoxication were lowest between ages 18-25 years and highest above age 65 years. Among older participants, men initiated alcohol use and regular drinking earlier, and had lower age at first intoxication than women, but among young adults, no sex differences were observed.

CONCLUSIONS

Alcohol consumption was high in the elderly Dutch population, especially among women. Alcohol initiation, onset of regular drinking, and first alcohol intoxication occur at increasingly younger ages, and the previous gap between men and women in age at alcohol initiation, onset of regular drinking, and first alcohol intoxication has closed almost entirely. Heavy alcohol use was most strongly predicted by older age, sex (male), and initiation of smoking and cannabis use.

A demonstration of the generalizability of twin-based research on antisocial behavior

Researchers typically analyze samples of twin pairs in order to decompose trait variance into genetic and environmental components. This methodological technique, referred to as twin-based research, rests on several assumptions that must be satisfied in order to produce unbiased results. While research has analyzed the tenability of certain assumptions such as equal environments, less attention has been given to whether results gleaned from samples of twins generalize to the broader population of non-twins. The current study analyzed data drawn from the National Longitudinal Study of Adolescent Health and findings suggested twins do not systematically differ from the general population of non-twins on many measures of behavior and development. Furthermore, the effects of specific covariates on measures of antisocial behavior did not appear to differ across twin status. In sum, evidence concerning the etiology of antisocial behavior (e.g., heritability estimates) gleaned from twin-based research is likely to generalize to the non-twin population.

Early concern and disregard for others as predictors of antisocial behavior

BACKGROUND

Prediction of antisocial behavior is important, given its adverse impact on both the individuals engaging in antisocial behavior and society. Additional research identifying early predictors of future antisocial behavior, or antisocial propensity, is needed. The present study tested the hypothesis that both concern for others and active disregard for others in distress in toddlers and young children predict antisocial behavior during middle childhood and adolescence.

METHODS

A representative sample of same-sex twins (N=956) recruited in Colorado was examined. Mother-rated and researcher-observed concern and disregard for others assessed at age 14-36 months were examined as predictors of parent- (age 4-12), teacher- (age 7-12), and self-reported (age 17) antisocial behavior.

RESULTS

  Observed disregard for others predicted antisocial behavior assessed by three different informants (parents, teachers, and self), including antisocial behavior assessed 14 years later. It also predicted a higher order antisocial behavior factor (β=.58, p<.01) after controlling for observed concern for others. Mother-rated disregard for others predicted parent-reported antisocial behavior. Contrary to predictions, neither mother-rated nor observed concern for others inversely predicted antisocial behavior. RESULTS of twin analyses suggested that the covariation between observed disregard for others and antisocial behavior was due to shared environmental influences.

CONCLUSIONS

Disregard for others in toddlerhood/early childhood is a strong predictor of antisocial behavior in middle childhood and adolescence. The results suggest the potential need for early assessment of disregard for others and the development of potential interventions.

The Young Netherlands Twin Register (YNTR): longitudinal twin and family studies in over 70,000 children

The Netherlands Twin Register (NTR) began in 1987 with data collection in twins and their families, including families with newborn twins and triplets. Twenty-five years later, the NTR has collected at least one survey for 70,784 children, born after 1985. For the majority of twins, longitudinal data collection has been done by age-specific surveys. Shortly after giving birth, mothers receive a first survey with items on pregnancy and birth. At age 2, a survey on growth and achievement of milestones is sent. At ages 3, 7, 9/10, and 12 parents and teachers receive a series of surveys that are targeted at the development of emotional and behavior problems. From age 14 years onward, adolescent twins and their siblings report on their behavior problems, health, and lifestyle. When the twins are 18 years and older, parents are also invited to take part in survey studies. In sub-groups of different ages, in-depth phenotyping was done for IQ, electroencephalography , MRI, growth, hormones, neuropsychological assessments, and cardiovascular measures. DNA and biological samples have also been collected and large numbers of twin pairs and parents have been genotyped for zygosity by either micro-satellites or sets of short nucleotide polymorphisms and repeat polymorphisms in candidate genes. Subject recruitment and data collection is still ongoing and the longitudinal database is growing. Data collection by record linkage in the Netherlands is beginning and we expect these combined longitudinal data to provide increased insights into the genetic etiology of development of mental and physical health in children and adolescents.

Childhood attention-deficit hyperactivity disorder as an extreme of a continuous trait: a quantitative genetic study of 8,500 twin pairs

BACKGROUND

Although the clinical utility of categorically defined attention-deficit hyperactivity disorder (ADHD) is well established, there is also strong evidence supporting the notion of ADHD as an extreme of a continuous trait. Nevertheless, the question of whether the etiology is the same for different levels of DSM-IV ADHD symptoms remains to be investigated. The aim of this study was to assess genetic links between the extreme and the subthreshold range of ADHD symptoms.

METHOD

Parents of all Swedish 9- and 12-year-old twins born between 1992 and 2000 were interviewed for DSM-IV ADHD symptoms and associated conditions. Two validated cutoff values were used for screening and assigning research diagnoses. Response rate was 80%. Twin methods were applied to investigate the extent to which ADHD is etiologically distinct from subthreshold variations in ADHD symptoms.

RESULTS

Extremes analyses indicated a strong genetic link between the extreme and the subthreshold variation, with almost identical group heritability estimates around .60 for the diagnostic (prevalence 1.78%) and screening (prevalence 9.75%) criteria of ADHD.

CONCLUSION

A strong genetic link between the extreme and the subthreshold variation of DSM-IV based assessments of ADHD symptoms was found. The data suggest that ADHD is best viewed as the quantitative extreme of genetic and environmental factors operating dimensionally throughout the distribution of ADHD symptoms, indicating that the same etiologic factors are involved in the full range of symptoms of inattention, hyperactivity and impulsivity.

Age-of-onset or behavioral sub-types? A prospective comparison of two approaches to characterizing the heterogeneity within antisocial behavior

There are two common approaches to sub-typing the well-documented heterogeneity within antisocial behavior: age-of-onset (i.e., childhood-onset versus adolescence-onset; see Moffitt 1993) and behavioral (i.e., physical aggression versus non-aggressive rule-breaking). These approaches appear to be associated, such that aggression is more characteristic of childhood-onset antisocial behavior whereas rule-breaking is linked to both child- and adolescence-onset antisocial behavior. However, it remains unclear which approach, if either, better explains the heterogeneity within antisocial behavior. We examined this question in a prospective sample of male twins, assessed at the ages of 11, 14, 17, and 24 years. Although the age-of-onset subtypes predicted adult antisocial behavior in the expected direction when analyzed alone, this association dissipated once we controlled for aggression and rule-breaking. Such findings suggest that the behavioral sub-types of antisocial behavior may be a stronger predictor of later antisocial outcomes than is its age-of-onset.

Pre-divorce problems in 3-year-olds: a prospective study in boys and girls

OBJECTIVE

We examined to what extent internalizing and externalizing problems at age 3 preceded and predicted parental divorce, and if divorce and the time lapse since divorce were related to internalizing and externalizing problems at age 12.

METHODS

Parental ratings of internalizing and externalizing problems were collected with the Child Behavior Checklist (CBCL) in a large sample (N = 6,426) of 3-year-old children. All these children were followed through the age of 12 years, at which parents completed the CBCL again, while teachers completed the Teacher's Report Form. Children whose parents divorced between age 3 and age 12 were compared with children whose families remained intact.

RESULTS

Girls whose parents divorced between ages 3 and 12 already showed more externalizing problems at age 3 than girls whose parents stayed married. Higher levels of externalizing problems in girls at age 3 predicted later parental divorce. Parental reports indicated that 12-year-olds with divorced parents showed more internalizing and externalizing problems than children with married parents. Levels of teacher-reported problems were not different between children with married versus divorced parents. However, children whose parents divorced between ages 3 and 12 showed more teacher-rated internalizing problems at age 12 when the divorce was more recent than when the divorce was less recent. Parental ratings of both internalizing and externalizing problems at age 12 were not associated with the time lapse since divorce.

CONCLUSION

Externalizing problems in girls precede and predict later parental divorce. Post-divorce problems in children vary by raters, and may depend on the time lapse since divorce.