Two babies, two bonds: Frequency and correlates of differential maternal-infant bonding in mothers of twins

We assessed prevalence and correlates of differential maternal-infant bonding (i.e., experiencing a stronger bond with one baby vs. the other) in mothers of twins, focusing on aspects of maternal mental health, well-being, and pregnancy/birth that have been previously linked with maternal-infant bonding. Participants (N = 108 American women, 88.89% White, 82.41% non-Hispanic, aged 18-45, who gave birth to twins in the past 6-24 weeks) were recruited from postpartum support websites. Participants completed a Qualtrics survey assessing pregnancy/birth history, symptoms of depression and anxiety, sleep, stress, romantic relationship satisfaction, and postpartum bonding. Twenty-six participants (24.07%) reported a bonding discrepancy. These participants endorsed higher symptoms of depression and anxiety, lower relationship satisfaction, lower average postpartum bonding, higher general and parenting stress, and longer pregnancy (all ps > .05). Greater degree of bonding discrepancy correlated with more depression, higher parenting stress, longer pregnancy, and lower relationship satisfaction (all ps > .05). Mothers of twins may benefit from postpartum mental health support, stress management strategies, and interventions to improve bonding. Future work should assess the role of breastfeeding difficulties, delivery method, birth-related trauma, infant regulatory capacity, and temperament. Longitudinal studies will help test cause and effect and potential long-term repercussions of maternal-infant bonding discrepancies.

Reduction in the use of green spaces during the COVID-19 pandemic and its impact on mental health

Our study examined the use of green spaces before and during the pandemic in a large cohort of Italian twins and evaluated its impact on measures of mental health (depressive, anxiety, stress symptoms). Twins were analysed as individuals and as pairs. A twin design approach was applied to minimize confounding by genetic and shared environmental factors. Questionnaires from 2,473 twins enrolled in the Italian Twin Registry were screened. Reduced green space use was associated with significantly higher levels of depression, anxiety and distress. Being a woman, residing in urban areas, and having a high perceived risk of the outbreak resulted in a higher likelihood to modify green space use, with a negative impact on mental health.

Parental criticism and adolescent internalising symptoms: using a Children-of-Twins design with power calculations to account for genetic influence

BACKGROUND

Parental criticism is correlated with internalising symptoms in adolescent offspring. This correlation could in part reflect their genetic relatedness, if the same genes influence behaviours in both parents and offspring. We use a Children-of-Twins design to assess whether parent-reported criticism and offspring internalising symptoms remain associated after controlling for shared genes. To aid interpretation of our results and those of previous Children-of-Twins studies, we examine statistical power for the detection of genetic effects and explore the direction of possible causal effects between generations.

METHODS

Data were drawn from two Swedish twin samples, comprising 876 adult twin pairs with adolescent offspring and 1,030 adolescent twin pairs with parents. Parent reports of criticism towards their offspring were collected concurrently with parent and offspring reports of adolescent internalising symptoms. Children-of-Twins structural equation models were used to control for genetic influence on the intergenerational association between parental criticism and adolescent internalising.

RESULTS

Parental criticism was associated with adolescent internalising symptoms after controlling for genetic influence. No significant role was found for shared genes influencing phenotypes in both generations, although power analyses suggested that some genetic effects may have gone undetected. Models could not distinguish directionality for nongenetic, causal effects between generations.

CONCLUSIONS

Parental criticism may be involved in psychosocial family processes in the context of adolescent internalising. Future studies should seek to identify these processes and provide clarity on the direction of potential causal effects.

Childhood maltreatment and disordered gambling in adulthood: disentangling causal and familial influences

BACKGROUND

Despite abundant research on the potential causal influence of childhood maltreatment (CM) on psychological maladaptation in adulthood, almost none has implemented the discordant twin design as a means of examining the role of such experiences in later disordered gambling (DG) while accounting for genetic and family environmental confounds. The present study implemented such an approach to disentangle the potential causal and familial factors that may account for the association between CM and DG.

METHODS

Participants were 3750 twins from the Australian Twin Registry [Mage = 37.60 (s.d. = 2.31); 58% female]. CM and DG were assessed separately via two semi-structured telephone interviews. Random-intercept generalized linear mixed models were fit to the data; zygosity, sex, educational attainment, childhood psychiatric disorder, adult antisocial behavior, and alcohol use disorder (AUD) were included as covariates.

RESULTS

Neither quasi-causal nor familial effects of CM predicted DG after adjusting for covariates. Educational attainment appeared to reduce the risk of DG while AUD appeared to increase risk; evidence also emerged for familial effects of antisocial behavior on DG. Post-hoc analyses revealed a familial effect of CM on antisocial behavior, indicating that the association between CM and DG identified in unadjusted models and in prior studies may be accounted for by genetic and shared family environmental effects of antisociality.

CONCLUSIONS

These findings add to the meager literature showing that CM does not exert a causal effect on DG, and present novel evidence that familial effects of antisocial behavior may account for the association between CM and DG identified in extant non-twin research.

Gene-Environment Interactions in Attention-Deficit/Hyperactivity Disorder Symptom Dimensions: The Role of Unhealthy Food Habits

Background: Dietary habits were investigated as environmental risk factors for Attention-Deficit/Hyperactivity Disorder (ADHD). However, no previous studies explored the effects of dietary factors on modifying the role of genetic factors on ADHD. Methods: Based on a Swedish population-based twin study with 1518 twin pairs aged 20-47 years, we tested whether the importance of genetic and environmental effects on ADHD varied as a function of dietary habits. Self-reported dietary habits and ADHD symptoms were collected. Twin methods were used to test the degree to which high-sugar and unhealthy food intake moderated the genetic and environmental influences on ADHD symptoms. Results: In middle-aged adults, genetic influences on inattention symptoms were statistically significantly higher among individuals with higher levels of high-sugar (45%, 95%CI: 25-54%) and unhealthy food intake (51%, 95%CI: 31-60%), compared with those with lower levels of consumption of high-sugar (36%, 95%CI: 25-47%) and unhealthy foods (30%, 95%CI: 20-41%). Similar patterns were also found for the associations between hyperactivity/impulsivity and high-sugar/unhealthy food intake, even though the moderation effects were not statistically significant. Conclusion The present study suggests that genetic factors play a more prominent role in individual differences of ADHD symptoms in the presence of the high consumption of sugar and unhealthy foods. Future longitudinal studies with multiple assessments of ADHD and dietary habits are needed to replicate our findings.

A Representational Similarity Analysis of Cognitive Control during Color-Word Stroop

Progress in understanding the neural bases of cognitive control has been supported by the paradigmatic color-word Stroop task, in which a target response (color name) must be selected over a more automatic, yet potentially incongruent, distractor response (word). For this paradigm, models have postulated complementary coding schemes: dorsomedial frontal cortex (DMFC) is proposed to evaluate the demand for control via incongruency-related coding, whereas dorsolateral PFC (DLPFC) is proposed to implement control via goal and target-related coding. Yet, mapping these theorized schemes to measured neural activity within this task has been challenging. Here, we tested for these coding schemes relatively directly, by decomposing an event-related color-word Stroop task via representational similarity analysis. Three neural coding models were fit to the similarity structure of multivoxel patterns of human fMRI activity, acquired from 65 healthy, young-adult males and females. Incongruency coding was predominant in DMFC, whereas both target and incongruency coding were present with indistinguishable strength in DLPFC. In contrast, distractor information was strongly encoded within early visual cortex. Further, these coding schemes were differentially related to behavior: individuals with stronger DLPFC (and lateral posterior parietal cortex) target coding, but weaker DMFC incongruency coding, exhibited less behavioral Stroop interference. These results highlight the utility of the representational similarity analysis framework for investigating neural mechanisms of cognitive control and point to several promising directions to extend the Stroop paradigm.SIGNIFICANCE STATEMENT How the human brain enables cognitive control - the ability to override behavioral habits to pursue internal goals - has been a major focus of neuroscience research. This ability has been frequently investigated by using the Stroop color-word naming task. With the Stroop as a test-bed, many theories have proposed specific neuroanatomical dissociations, in which medial and lateral frontal brain regions underlie cognitive control by encoding distinct types of information. Yet providing a direct confirmation of these claims has been challenging. Here, we demonstrate that representational similarity analysis, which estimates and models the similarity structure of brain activity patterns, can successfully establish the hypothesized functional dissociations within the Stroop task. Representational similarity analysis may provide a useful approach for investigating cognitive control mechanisms.

The causal nature of the association between resting pulse in late adolescence and risk for internalizing and externalizing disorders: a co-relative analysis in a national male Swedish sample

BACKGROUND

Resting pulse is robustly and inversely associated with the risk for externalizing disorders and may be positively associated with internalizing disorders. We know little about the causal nature of these associations.

METHODS

We examined resting pulse at conscription examination in 369 301 males born 1960-80 with a mean (s.d.) follow-up of 29.1 (7.7) years. From pulse rates, we predicted, using Cox models, the risk for criminal behavior (CB), drug abuse (DA), alcohol use disorder (AUD), major depression (MD), and anxiety disorders (AD), assessed from medical, criminal, and pharmacy registries. Co-relative analyses were conducted on the general population, cousin, half-sibling, full-sibling, and monozygotic pairs discordant for the outcome. Twin/sibling modeling for pulse was performed using OpenMX.

RESULTS

Familial resemblance for pulse resulted entirely from genetic factors. In the general population, the risk for externalizing disorders (CB, DA, and AUD) and internalizing disorders (MD and AD) were, respectively, significantly associated with low and high resting pulse rate. For CB, DA, and AUD, co-relative analyses showed that the inverse association with pulse resulted entirely from familial common causes (aka 'confounders'). By contrast, co-relative analyses found that the association between higher pulse and MD and AD resulted from direct causal effects.

CONCLUSIONS

Resting pulse has a negative and positive association with, respectively, the risk for externalizing and for internalizing disorders. Co-relative analyses indicate that the nature of these associations differ, suggesting that elevated pulse appears to directly increase the risk for internalizing disorders while the reduced pulse is a risk index for underlying traits that predispose to externalizing disorders.

Network dynamics of momentary affect states and future course of psychopathology in adolescents

BACKGROUND

Recent theories argue that an interplay between (i.e., network of) experiences, thoughts and affect in daily life may underlie the development of psychopathology.

OBJECTIVE

To prospectively examine whether network dynamics of everyday affect states are associated with a future course of psychopathology in adolescents at an increased risk of mental disorders.

METHODS

159 adolescents from the East-Flanders Prospective Twin Study cohort participated in the study. At baseline, their momentary affect states were assessed using the Experience Sampling Method (ESM). The course of psychopathology was operationalized as the change in the Symptom Checklist-90 sum score after 1 year. Two groups were defined: one with a stable level (n = 81) and one with an increasing level (n = 78) of SCL-symptom severity. Group-level network dynamics of momentary positive and negative affect states were compared between groups.

RESULTS

The group with increasing symptoms showed a stronger connections between negative affect states and their higher influence on positive states, as well as higher proneness to form 'vicious cycles', compared to the stable group. Based on permutation tests, these differences were not statistically significant.

CONCLUSION

Although not statistically significant, some qualitative differences were observed between the networks of the two groups. More studies are needed to determine the value of momentary affect networks for predicting the course of psychopathology.

Familial coaggregation of major psychiatric disorders among first-degree relatives of patients with obsessive-compulsive disorder: a nationwide study

BACKGROUND

Whether the first-degree relatives (FDRs) of patients with obsessive-compulsive disorder (OCD) have an increased risk of the major psychiatric disorders, namely schizophrenia, bipolar disorder, OCD, major depressive disorder (MDD), autism spectrum disorder (ASD), and attention deficit hyperactivity disorder (ADHD), remains unclear.

METHODS

Using the Taiwan National Health Insurance Research Database with the whole population sample size (n = 23 258 175), 89 500 FDRs, including parents, offspring, siblings, and twins, of patients with OCD were identified in our study. The relative risks (RRs) of major psychiatric disorders were assessed among FDRs of patients with OCD.

RESULTS

FDRs of patients with OCD had higher RRs of major psychiatric disorders, namely OCD (RR 8.11, 95% confidence interval (CI) 7.68-8.57), bipolar disorder (RR 2.85, 95% CI 2.68-3.04), MDD (RR 2.67, 95% CI 2.58-2.76), ASD (RR 2.38, 95% CI 2.10-2.71), ADHD (RR 2.19, 95% CI 2.07-2.32), and schizophrenia (RR 1.97, 95% CI 1.86-2.09), compared with the total population. Different familial kinships of FDRs, such as parents, offspring, siblings, and twins consistently had increased risks for these disorders. In addition, a dose-dependent relationship was found between the numbers of OCD probands and the risk of each major psychiatric disorder.

CONCLUSIONS

The FDRs, including parents, offspring, siblings, and twins, of patients with OCD have a higher risk of OCD, schizophrenia, bipolar disorder, MDD, ADHD, and ASD. The familial co-aggregation of OCD with OCD and other major psychiatric disorders was existent in a dose-dependent manner. Given the increased risks of psychiatric disorders, medical practitioners should closely monitor the mental health of the FDRs of patients with OCD.

Are changes in ADHD course reflected in differences in IQ and executive functioning from childhood to young adulthood?

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is associated with poorer cognitive functioning. We used a developmental, genetically-sensitive approach to examine intelligence quotient (IQ) from early childhood to young adulthood among those with different ADHD courses to investigate whether changes in ADHD were reflected in differences in IQ. We also examined executive functioning in childhood and young adulthood among different ADHD courses.

METHODS

Study participants were part of the Environmental Risk (E-Risk) Longitudinal Twin Study, a population-based birth cohort of 2232 twins. We assessed ADHD in childhood (ages 5, 7, 10 and 12) and young adulthood (age 18). We examined ADHD course as reflected by remission, persistence and late-onset. IQ was evaluated at ages 5, 12 and 18, and executive functioning at ages 5 and 18.

RESULTS

ADHD groups showed deficits in IQ across development compared to controls; those with persistent ADHD showed the greatest deficit, followed by remitted and late-onset. ADHD groups did not differ from controls in developmental trajectory of IQ, suggesting changes in ADHD were not reflected in IQ. All ADHD groups performed more poorly on executive functioning tasks at ages 5 and 18; persisters and remitters differed only on an inhibitory control task at age 18.

CONCLUSIONS

Differences in ADHD course - persistence, remission and late-onset - were not directly reflected in changes in IQ. Instead, having ADHD at any point across development was associated with lower average IQ and poorer executive functioning. Our finding that individuals with persistent ADHD have poorer response inhibition than those who remitted requires replication.

Marriage and reductions in men's alcohol, tobacco, and cannabis use

BACKGROUND

Psychoactive substance use is lower among married compared to divorced or unmarried men; yet, the nature of this effect remains unclear because becoming and staying married is potentially confounded with substance-related background familial and individual factors, like parental divorce and personality. The authors investigated the associations between marital status and substance use; how substance use changed across the transition to marriage; and whether marriage effects were likely to be causal.

METHOD

The sample included 1790 adults from male-male twin pairs from a population-based registry. Measures of marital status and alcohol, tobacco, and cannabis use came from Life History Calendars. Data were analyzed using regression, co-twin comparison, and within-person models. The latter models are tools for quasi-causal inference that control for familial and individual-level confounders.

RESULTS

Married men used less alcohol, tobacco, and cannabis than men who were divorced/separated or single. In analyses of substance use across the transition to marriage, men reduced their alcohol and cannabis use both before and after marriage, but their tobacco use only after marriage. These effects were largely robust in co-twin and within-person analyses.

CONCLUSIONS

Marriage was associated with substantial reductions in substance use compared to being divorced/separated or single, and these reductions began prior to marriage. The co-twin comparison and within-person models ruled out the alternative explanation that marriage effects were due to confounding background familial and individual factors. These results provide strong evidence that the social role expectations associated with marriage reduce psychoactive substance use.

Adolescents' perceptions of family social status correlate with health and life chances: A twin difference longitudinal cohort study

Children from lower-income households are at increased risk for poor health, educational failure, and behavioral problems. This social gradient is one of the most reproduced findings in health and social science. How people view their position in social hierarchies also signals poor health. However, when adolescents' views of their social position begin to independently relate to well-being is currently unknown. A cotwin design was leveraged to test whether adolescents with identical family backgrounds, but who viewed their family's social status as higher than their same-aged and sex sibling, experienced better well-being in early and late adolescence. Participants were members of the Environmental Risk Longitudinal Twin Study, a representative cohort of British twins (n = 2,232) followed across the first 2 decades of life. By late adolescence, perceptions of subjective family social status (SFSS) robustly correlated with multiple indicators of health and well-being, including depression; anxiety; conduct problems; marijuana use; optimism; not in education, employment, or training (NEET) status; and crime. Findings held controlling for objective socioeconomic status both statistically and by cotwin design after accounting for measures of childhood intelligence (IQ), negative affect, and prior mental health risk and when self-report, informant report, and administrative data were used. Little support was found for the biological embedding of adolescents' perceptions of familial social status as indexed by inflammatory biomarkers or cognitive tests in late adolescence or for SFSS in early adolescence as a robust correlate of well-being or predictor of future problems. Future experimental studies are required to test whether altering adolescents' subjective social status will lead to improved well-being and social mobility.

Reciprocal links between anxiety sensitivity and obsessive-compulsive symptoms in youth: a longitudinal twin study

BACKGROUND

Anxiety sensitivity, the tendency to fear the symptoms of anxiety, is a key risk factor for the development anxiety disorders. Although obsessive-compulsive disorder was previously classified as an anxiety disorder, the prospective relationship between anxiety sensitivity and obsessive-compulsive symptoms (OCS) has been largely overlooked. Furthermore, a lack of genetically informative studies means the aetiology of the link between anxiety sensitivity and OCS remains unclear.

METHODS

Adolescent twins and siblings (N = 1,579) from the G1219 study completed self-report questionnaires two years apart assessing anxiety sensitivity, OCS, anxiety and depression. Linear regression models tested prospective associations between anxiety sensitivity and OCS, with and without adjustment for anxiety and depressive symptoms. A phenotypic cross-lagged model assessed bidirectional influences between anxiety sensitivity and OCS over time, and a genetic version of this model examined the aetiology of these associations.

RESULTS

Anxiety sensitivity was prospectively associated with changes in OCS, even after controlling for comorbid anxiety and depressive symptoms. The longitudinal relationship between anxiety sensitivity and OCS was bidirectional, and these associations were predominantly accounted for by nonshared environmental influences.

CONCLUSIONS

Our findings are consistent with the notion that anxiety sensitivity is a risk factor for OCS during adolescence, but also suggest that experiencing OCS confers risk for heightened anxiety sensitivity. The reciprocal links between OCS and anxiety sensitivity over time are likely to be largely mediated by nonshared environmental experiences, as opposed to common genes. Our findings raise the possibility that interventions aimed at ameliorating anxiety sensitivity could reduce risk for OCS, and vice versa.

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.

Using discordant twin methods to investigate an environmentally mediated pathway between social support and the reduced likelihood of adolescent psychotic experiences

BACKGROUND

Social support has been shown to be associated with a reduced likelihood of developing psychotic experiences in the general population and even amongst those at high risk due to exposure to multiple forms of victimisation (poly-victimised). However, it is unclear whether this association is merely due to the confounding effects of shared environmental and genetic influences, or reverse causality. Therefore, we investigated whether social support has a unique environmentally mediated effect on adolescent psychotic experiences after accounting for familial factors, including genetic factors, and also prior psychopathology.

METHODS

Participants were from the Environmental Risk (E-Risk) Longitudinal Twin Study, a nationally-representative cohort of 2232 UK-born twins. Adolescents were interviewed at age 18 about psychotic experiences and victimisation exposure since age 12, and their perceptions of social support. Prior childhood mental health problems and psychotic symptoms were assessed at age 12. The discordant twin method was used to disentangle the relative family-wide and unique-environmental effects of social support on psychotic experiences in the general population and among poly-victimised adolescents.

RESULTS

Perceived social support, particularly from friends, was found to have a unique environmentally mediated buffering effect on adolescent psychotic experiences in the whole sample and in the high-risk poly-victimised group.

CONCLUSIONS

The protective effects of social support on adolescent psychotic experiences cannot be accounted for by shared environmental or genetic factors, nor by earlier psychopathology. Our findings suggest that early intervention programmes focused on increasing perceptions of social support have the potential to prevent the emergence of psychotic experiences amongst adolescents.

Do neighborhood social processes moderate the etiology of youth conduct problems?

BACKGROUND

Prior work has robustly suggested that social processes in the neighborhood (i.e. informal social control, social cohesion, norms) influence child conduct problems (CP) and related outcomes, but has yet to consider how these community-level influences interact with individual-level genetic risk for CP. The current study sought to do just this, evaluating neighborhood-level social processes as etiologic moderators of child CP for the first time.

METHODS

We made use of two nested samples of child and adolescent twins within the Michigan State University Twin Registry (MSUTR): 5649 families who participated in in the Michigan Twins Project (MTP) and 1013 families who participated in the Twin Study of Behavioral and Emotional Development (TBED-C). The neighborhood social processes of informal social control, social cohesion, and norms were assessed using neighborhood sampling techniques, in which residents of each twin family's neighborhood reported on the social processes in their neighborhood. Standard biometric GxE analyses evaluated the extent to which they moderated the etiology of CP.

RESULTS

The 'no moderation' model provided the best fit to the data in nearly all cases, arguing against neighborhood social processes as etiologic moderators of youth CP.

CONCLUSIONS

The neighborhood social processes evaluated here do not appear to exert their effects on child CP via etiologic moderation. The documented links between neighborhood social processes and child CP are thus likely to reflect a different etiologic process. Possibilities include environmental main effects of neighborhood social processes on child CP, or genotype-environment correlations.

Internalizing and externalizing psychopathology in middle age: genetic and environmental architecture and stability of symptoms over 15 to 20 years

BACKGROUND

Internalizing and externalizing psychopathology factors explain much of the covariance among psychiatric conditions, especially at the level of genetic risk. However, few studies have examined internalizing and externalizing factors in middle-aged samples, especially their ability to predict later symptoms across midlife. The goals of the current study were (i) to quantify the genetic and environmental influences on internalizing and externalizing psychopathology in individuals in their early 40s, and (ii) examine the extent to which these genetic and environmental influences predict self-reported measures of internalizing and externalizing symptoms 15-20 years later.

METHOD

1484 male twins completed diagnostic interviews of psychopathology at mean age 41 and self-reported measures of anxiety, depression, substance use, and related variables at up to two time-points in late middle age (mean ages 56 and 62).

RESULTS

Structural equation modeling of the diagnostic interviews confirmed that internalizing and externalizing factors accounted for most of the genetic variance in individual disorders, with substantial genetic (ra = 0.70) and environmental (re = 0.77) correlations between the factors. Internalizing psychopathology at age 41 was correlated with latent factors capturing anxiety, depression, and/or post-traumatic stress symptoms at ages 56 (r = 0.51) and 62 (r = 0.43). Externalizing psychopathology at age 41 was correlated r = 0.67 with a latent factor capturing aggression, tobacco use, and alcohol use at age 56. Stability of both factors was driven by genetic influences.

CONCLUSIONS

These findings demonstrate the considerable stability of internalizing and externalizing psychopathology symptoms across middle age, especially their genetic influences. Diagnostic interviews effectively predict self-reported symptoms and behaviors 15-20 years later.

A Genetically Informed Study of Neighborhoods and Health: Results From the MIDUS Twin Sample

OBJECTIVES

To examine whether neighborhood income and neighborhood safety concerns influence multisystem physiological risk after adjusting for genetic and environmental selection effects that may have biased previous tests of this association.

METHODS

We used structural equation modeling with a genetically informed sample of 686 male and female twin pairs in the Midlife in the United States Study II (2004).

RESULTS

Controlling for additive genetic and shared environmental processes that may have biased neighborhood-health links in previous examinations, higher neighborhood safety concerns were associated with less physiological risk among women but not men.

DISCUSSION

Our findings suggest a possible causal role of neighborhood features for a measure of physiological risk that is associated with the development of disease. Efforts to increase neighborhood safety, perhaps through increased street lighting or neighborhood watch programs, may improve community-level health.

Evolving Connectionist Models to Capture Population Variability across Language Development: Modeling Children's Past Tense Formation

Children's acquisition of the English past tense has been widely studied as a testing ground for theories of language development, mostly because it comprises a set of quasi-regular mappings. English verbs are of two types: regular verbs, which form their past tense based on a productive rule, and irregular verbs, which form their past tenses through exceptions to that rule. Although many connectionist models exist for capturing language development, few consider individual differences. In this article, we explore the use of populations of artificial neural networks (ANNs) that evolve according to behavioral genetics principles in order to create computational models capable of capturing the population variability exhibited by children in acquiring English past tense verbs. Literature in the field of behavioral genetics views variability in children's learning in terms of genetic and environmental influences. In our model, the effects of genetic influences are simulated through variations in parameters controlling computational properties of ANNs, and the effects of environmental influences are simulated via a filter applied to the training set. This filter alters the quality of information available to the artificial learning system and creates a unique subsample of the training set for each simulated individual. Our approach uses a population of twins to disentangle genetic and environmental influences on past tense performance and to capture the wide range of variability exhibited by children as they learn English past tenses. We use a novel technique to create the population of ANN twins based on the biological processes of meiosis and fertilization. This approach allows modeling of both individual differences and development (within the lifespan of an individual) in a single framework. Finally, our approach permits the application of selection on developmental performance on the quasi-regular task across generations. Setting individual differences within an evolutionary framework is an important and novel contribution of our work. We present an experimental evaluation of this model, focusing on individual differences in performance. The experiments led to several novel findings, including: divergence of population attributes during selection to favor regular verbs, irregular verbs, or both; evidence of canalization, analogous to Waddington's developmental epigenetic landscape, once selection starts targeting a particular aspect of the task domain; and the limiting effect on the power of selection in the face of stochastic selection (roulette wheel), sexual reproduction, and a variable learning environment for each individual. Most notably, the heritability of traits showed an inverse relationship to optimization. Selected traits show lower heritability as the genetic variation of the population reduces. The simulations demonstrate the viability of linking concepts such as heritability of individual differences, cognitive development, and selection over generations within a single computational framework.

On the etiology of internalizing and externalizing problem behavior: A twin-family study

Internalizing and externalizing behavior problems are established risk factors for many unpleasant outcomes and psychopathology in adulthood, and understanding the interplay between genes and environment is important for deducing implications for therapeutic interventions. Among genetic studies on internalizing and externalizing problem behavior, the heritability estimates differ widely. Most research only uses twin data and other-reports, and therefore certain limitations are inevitable. Our study is the first to investigate genetic and environmental influences on problem behavior using a Nuclear Twin Family Design and self-reports, in order to address these limitations. Internalizing and externalizing problem behavior of 3,087 twin pairs (age 11–23), a sibling, and their parents were analyzed with structural equation modeling to estimate heritability separately for each of three twin birth cohorts. Genetic influences account for about one-third of the variance for both internalizing and externalizing. Shared environmental influences were only found for internalizing, and through the advantages of considering data from the whole twin family, firstly could be identified as solely twin-specific. Our findings could contribute to a better understanding of the gap between heritability based on twin studies and DNA-based heritability (‘missing heritability problem’): Results indicate that heritability estimates gained via classic twin design and other-reports are slightly overestimated and therefore environmental influences, in general, are more important than previous research suggests. Simultaneously, we showed that family-specific environment either contributes to behavior problems only on an individual level, or that it has a lesser influence than originally thought.

The relationship between independent and dependent life events and depression symptoms in Sri Lanka: a twin and singleton study

PURPOSE

Life events have been associated with a variety of mental health conditions including depression. There is a scarcity of research in South Asia exploring the aetiology of independent and dependent life events and their relationship with depression symptoms. This study aimed, in a Sri Lankan population, to identify the socio-demographic correlates and genetic and environmental influences on independent and dependent life events and their relationship with depression.

METHODS

Questionnaire data came from the Colombo Twin and Singleton Follow-up Study, CoTaSS-2 (N = 3969), a population study of Sri Lankan twins and singletons. Lifetime-ever independent and dependent life events were measured using a questionnaire and depressive symptoms using the Revised Beck's Depression Inventory. Structural Equation Model-fitting analyses explored the genetic and environmental influences on life events and depression.

RESULTS

Living in a rural environment and financial hardship were associated with greater reporting of independent and dependent life events. Sex differences were evident in the aetiology of life events and depression symptoms. Independent and dependent life events, but not depression symptoms, were heritable in males. Independent life events and depression symptoms, but not dependent life events, were heritable in females. Non-shared environmental influences explained phenotypic associations between independent life events and depression symptoms in both males and females. Genetic and non-shared environmental influences explained the phenotypic associations between dependent life events and depression symptoms in males. Only non-shared environment explained the covariation between dependent life events and depression symptoms in females.

CONCLUSIONS

Socio-demographic correlates of independent and dependent life events were similar to those reported in Western populations. Life events were associated with increased depression symptoms. Contrary to research in Western populations, we found that non-shared environmental, rather than genetic, influences explained much of the covariation between life events and depression symptoms. This suggests that whilst independent LEs may be heritable, the relationship is unlikely to be confounded by genetic influences and has significant implications for possible interventions for depression.

Investigating the causal effect of cannabis use on cognitive function with a quasi-experimental co-twin design

BACKGROUND

It is unclear whether cannabis use causes cognitive decline; several studies show an association between cannabis use and cognitive decline, but quasi-experimental twin studies have found little support for a causal effect. Here, we evaluate the association of cannabis use with general cognitive ability and executive functions (EFs) while controlling for genetic and shared environmental confounds in a longitudinal twin study.

METHODS

We first examined the phenotypic associations between cannabis initiation, frequency, and use disorder with cognitive abilities, while also controlling for pre-use general cognitive ability and other substance involvement. We tested the concurrent association between the cannabis use variables and cognitive abilities in late adolescence and young adulthood and the longitudinal association between cannabis use variables during adolescence and young adulthood cognitive abilities. Next, we used multilevel models to test whether these relations reflect between- and/or within-twin pair associations.

RESULTS

Phenotypically, cannabis use was related to poorer cognitive functioning, although most associations were negligible after accounting for other substance use. Nevertheless, there were few significant within-family twin-specific associations, except that age 17 cannabis frequency was associated with worse age 23 Common EF and general cognitive ability.

CONCLUSIONS

We found little support for a potential causal effect of cannabis use on cognition, consistent with previous twin studies. Results suggest that cannabis use may not cause decline in cognitive ability among a normative sample of cannabis users.

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.

Assessing autism in females: The importance of a sex-specific comparison

Autism spectrum disorder (ASD) is diagnosed more often in boys than girls. Here, we compared the degree of autism - and related disorders - symptomatology in boys and girls with a registered diagnosis of ASD. We used parent telephone interview A-TAC (Autism-Tics, ADHD and other Comorbidities) ratings of 30,392 twins aged 9 or 12 (including 308 boys and 122 girls with National Patient Register diagnoses of ASD) participating in the Child and Adolescent Twin Study in Sweden. We used z-scores for ASD-symptoms, standardized separately for boys and girls. Boys with a diagnosis of ASD had a higher raw mean score than girls with a diagnosis on the A-TAC ASD domain. However, utilizing the z-scores, girls with a diagnosis of ASD deviated further away from the female population mean than did the boys with ASD from the male population mean. Girls also had higher standardized mean values for symptoms of Attention-Deficit/Hyperactivity Disorder, Learning Disabilities and Oppositional Defiant Disorder. The findings suggest that girls diagnosed with autism may represent an even more extreme end of the female population autistic features distribution, than diagnosed boys from the male population autistic features distribution. Future studies may benefit from examining the use of sex-specific cut-off scores.

Protocol for establishing a child and adolescent twin register for mental health research and capacity building in Sri Lanka and other low and middle-income countries in South Asia

INTRODUCTION

Worldwide, 10%-20% of children and adolescents experience mental health conditions. However, most such disorders remain undiagnosed until adolescence or adulthood. Little is known about the factors that influence mental health in children and adolescents, especially in low and middle-income countries (LMIC), where environmental threats, such as poverty and war, may affect optimal neurodevelopment. Cohort studies provide important information on risks and resilience across the life course by enabling tracking of the effects of early life environment on health during childhood and beyond. Large birth cohort studies, including twin cohorts that can be aetiologically informative, have been conducted within high-income countries but are not generalisable to LMIC. There are limited longitudinal birth cohort studies in LMIC.

METHODS

We sought to enhance the volume of impactful research in Sri Lanka by establishing a Centre of Excellence for cohort studies. The aim is to establish a register of infant, child and adolescent twins, including mothers pregnant with twins, starting in the districts of Colombo (Western Province) and Vavuniya (Northern Province). We will gain consent from twins or parents for future research projects. This register will provide the platform to investigate the aetiology of mental illness and the impact of challenges to early brain development on future mental health. Using this register, we will be able to conduct research that will (1) expand existing research capacity on child and adolescent mental health and twin methods; (2) further consolidate existing partnerships and (3) establish new collaborations. The initiative is underpinned by three pillars: high-quality research, ethics, and patient and public involvement and engagement (PPIE).

ETHICS AND DISSEMINATION

Ethical approval for this study was obtained from the Ethics Review Committee of Sri Lanka Medical Association and Keele University's Ethical Review Panel. In addition to journal publications, a range of PPIE activities have been conducted.

Genetic and Environmental Influences on Adolescent Emotional Inertia in Daily Life

Emotional inertia represents the extent to which individuals' emotions tend to carry over from one time point to the next. High emotional inertia indicates low emotion regulation ability and has been associated with psychological maladjustment and mood disorders. However, the extent of genetic influence on emotional inertia, particularly in adolescents, is largely unknown. The current study examined genetic and environmental influences on individual differences in emotional inertia. This study followed a sample of 447 17-year-old same-sex UK twins (41% males) with an innovative intensive longitudinal daily diary design that captured their intra-individual emotion fluctuations over one month. Adolescents reported their positive and negative emotions once a day consecutively for up to 40 days. Time series analyses were used to construct emotional inertia and classical twin analyses were used to disentangle its genetic and environmental influences. The results showed that inertia for positive emotion was only modestly heritable and inertia for negative emotion showed no heritability at all. Both measures showed predominantly non-shared environmental influences. These findings highlight the importance of unique environmental influences in shaping individual differences in how well adolescents regulate their emotions and how easily they move from one emotional state to another in daily life. The importance of identifying specific environmental influences on emotional inertia is discussed, and suggestions of what those influences might be are offered.

A within-sibling pair analysis of lifestyle behaviours and BMI z-score in the multi-centre I.Family study

BACKGROUND AND AIMS

By investigating differences in lifestyle behaviours and BMI in sibling pairs, family-level confounding is minimized and causal inference is improved, compared to cross-sectional studies of unrelated children. Thus, we aimed to investigate within-sibling pair differences in different lifestyle behaviours and differences in BMI z-scores in children and adolescents.

METHODS AND RESULTS

We examined three groups of sibling pairs 1) all same-sex sibling pairs with maximum 4 years age difference (n = 1209 pairs from 1072 families in 8 countries, mean age 10.7 years, standard deviation 2.4 years), 2) sibling pairs discordant for overweight (n = 262) and 3) twin pairs (n = 85). Usual dietary intake was estimated by 24-h recalls and time spent in light (LPA) and moderate-to-vigorous physical activity (MVPA) was measured by accelerometers. Screen time, sleep and dieting for weight loss were assessed by questionnaires. Within all 3 groups of sibling pairs, more time in MVPA was associated with lower BMI z-score. Higher energy intake was associated with higher BMI z-score within twin pairs and within all sibling pairs who were not currently dieting for weight loss. Regarding LPA, screen time or sleep duration, no or inconsistent associations were observed for the three groups of sibling pairs.

CONCLUSIONS

MVPA and energy intake were associated with BMI differences within sibling and twin pairs growing up in the same home, thus independent of family-level confounding factors. Future studies should explore whether genetic variants regulating appetite or energy expenditure behaviours account for weight differences in sibling pairs.

Outrageous fortune or destiny? Family influences on status achievement in the early life course

Psychologists using quantitative studies of the trait intelligence have established with much confidence that the impact of genes on intelligence increases with age, while the environmental effect of the family of origin declines. We examined the conjecture that a similar trend of increasing effect of genes/declining family environmental effect characterizes other status-related outcomes when arranged in typical age-graded sequence over adolescence and early adulthood. We used DeFries-Fulker (1985) (DF) analysis with longitudinal data on 1,576 pairs of variously-related young adult siblings (MZ twins; DZ twins; full siblings; half siblings; cousins; and nonrelated siblings; mean age 28) to estimate univariate quantitative genetic decompositions for fifteen status-related outcomes roughly ordered along the early life course: Verbal IQ, High school GPA, College plans, High school graduation, Some college, College graduation, Graduate school, Educational attainment, Occupational education, Occupational wages, Personal earnings, Household income, Household assets, Home ownership, and Subjective social status, with and without covariate controls for Age, Female gender, and Race/ethnicity (black, Hispanic, other; reference white). Results for successive outcomes did not support the conjecture of increasing heritability with maturity. Rather, the impacts of both the genes and the family environment tended to decline over the life course, resulting in a downward trend in family influences from all sources. There was some evidence of a recrudescence in relative influence of the family environment for outcomes related to the household that are often shared with a spouse, such as home ownership, suggesting a role of assortative mating in status reproduction. Other findings and limitations of the study are discussed.

The interaction of sociodemographic risk factors and measures of nicotine dependence in predicting maternal smoking during pregnancy

BACKGROUND

Understanding differences in nicotine dependence assessments' ability to predict smoking cessation is complicated by variation in quit attempt contexts. Pregnancy reduces this variation, as each pregnant smoker receives the same strong cessation incentive. Cigarette smoking during pregnancy (SDP) provides a powerful paradigm for analyzing the interplay between nicotine dependence measures and sociodemographics in predicting cessation failure.

METHODS

Data from a female twin cohort (median birth year 1980), assessed in teens and early twenties, were merged with birth records to identify those with smoking history who experienced childbirth (N = 1657 births, N = 763 mothers). Logistic regression predicting SDP, as a function of birth record sociodemographic variables, generated a sociodemographic risk-score. Further analysis incorporated the risk-score with data from research interviews on DSM-IV-Nicotine Dependence symptom count, Heaviness of Smoking Index.

RESULTS

Low maternal educational level, younger age at childbirth, and being unmarried all contributed risk for SDP. In addition to sociodemographic risk-score, the best predictors of SDP included HSI-score (OR:1.51), their two-way interaction (OR:0.39; reduced impact of dependence at intermediate-high sociodemographic risk), history of ≥ two failed quit attempts (OR:1.38), and a dummy variable for prior pregnancy at time of assessment (OR:1.82). DSM-IV-Nicotine Dependence symptoms underperformed the Heaviness of Smoking Index and did not improve prediction when added to the best model.

CONCLUSIONS

The 2-item Heaviness of Smoking Index measure and report of ≥ two failed quit attempts performed best for predicting SDP. The contribution of either nicotine dependence measure to SDP risk was diminished at increased levels of sociodemographic risk.

Aggressive behaviour in childhood and adolescence: the role of smoking during pregnancy, evidence from four twin cohorts in the EU-ACTION consortium

BACKGROUND

Maternal smoking during pregnancy (MSDP) has been linked to offspring's externalizing problems. It has been argued that socio-demographic factors (e.g. maternal age and education), co-occurring environmental risk factors, or pleiotropic genetic effects may account for the association between MSDP and later outcomes. This study provides a comprehensive investigation of the association between MSDP and a single harmonized component of externalizing: aggressive behaviour, measured throughout childhood and adolescence.

METHODS

Data came from four prospective twin cohorts - Twins Early Development Study, Netherlands Twin Register, Childhood and Adolescent Twin Study of Sweden, and FinnTwin12 study - who collaborate in the EU-ACTION consortium. Data from 30 708 unrelated individuals were analysed. Based on item level data, a harmonized measure of aggression was created at ages 9-10; 12; 14-15 and 16-18.

RESULTS

MSDP predicted aggression in childhood and adolescence. A meta-analysis across the four samples found the independent effect of MSDP to be 0.4% (r = 0.066), this remained consistent when analyses were performed separately by sex. All other perinatal factors combined explained 1.1% of the variance in aggression across all ages and samples (r = 0.112). Paternal smoking and aggressive parenting strategies did not account for the MSDP-aggression association, consistent with the hypothesis of a small direct link between MSDP and aggression.

CONCLUSIONS

Perinatal factors, including MSDP, account for a small portion of the variance in aggression in childhood and adolescence. Later experiences may play a greater role in shaping adolescents' aggressive behaviour.

Openness declines in advance of death in late adulthood

Openness to experience has been found to be a correlate of successful aging outcomes yet also has been found to decline from middle age onward. We hypothesized that decline in openness would be associated with death. Using longitudinal data from the Swedish Adoption/Twin Study of Aging (SATSA), the analytic sample encompassed 1954 individuals, approximately two-thirds of whom were deceased. We tested whether openness declines across late adulthood and, central to our hypothesis, whether the decline correlated with age at death. Multivariate modeling adjusted for age at study entry, sex, education, as well as the time-varying effects of physical illness, depressive symptoms, and cognitive ability. Correlations between change in neuroticism and extraversion and death were modeled for comparison. A follow-up cotwin control analysis adjusted for genetic and environmental familial confounders. Significant mean-level change was identified in all personality traits, but only for openness was change correlated with age at death, in support of our hypothesis. The findings were not explained by health factors or cognition. Cotwin control analyses indicated that the twin who died earlier showed a greater drop in openness prior to death, compared with their cotwin measured at the same time points. There was no cotwin finding for neuroticism or extraversion. We suggest that declines in openness may reflect a change in goal orientation due to the experience of a shortened time horizon, leading to an optimized selection of experiences as people approach the end of life. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Genetically Informative Mediation Modeling Applied to Stressors and Personality-Disorder Traits in Etiology of Alcohol Use Disorder

A statistical mediation model was developed within a twin design to investigate the etiology of alcohol use disorder (AUD). Unlike conventional statistical mediation models, this biometric mediation model can detect unobserved confounding. Using a sample of 1410 pairs of Norwegian twins, we investigated specific hypotheses that DSM-IV personality-disorder (PD) traits mediate effects of childhood stressful life events (SLEs) on AUD, and that adulthood SLEs mediate effects of PDs on AUD. Models including borderline PD traits indicated unobserved confounding in phenotypic path coefficients, whereas models including antisocial and impulsive traits did not. More than half of the observed effects of childhood SLEs on adulthood AUD were mediated by adulthood antisocial and impulsive traits. Effects of PD traits on AUD 5‒10 years later were direct rather than mediated by adulthood SLEs. The results and the general approach contribute to triangulation of developmental origins for complex behavioral disorders.

The Transition of Sleep Behaviors in Twin Infants and Their Mothers in Early Infancy

BACKGROUND

The mothers of twins often suffer from sleeplessness. However, little is known about the relation of sleep behaviors between these mothers and their infants. The change of this relation with age has not been reported. The aims of this study are firstly to clarify the sleep behaviors of twin infants and their mothers by using actigraphy (four measurement periods at approximately 4- to 6-week intervals) and secondary to evaluate the relations of sleep behaviors between twin infants and their mothers.

METHODS

Five twin pairs and their mothers (first-time mother) were participated in this prospective longitudinal study. Their sleep behaviors were recorded for 7 consecutive days by using an actigraph, when the infants reached a corrected age (CA) of 3-6 weeks, 8-11 weeks, 13-15 weeks, and 17-20 weeks. Sleep status was classified into 3 states: both infants sleeping, only one infant sleeping, and both infants awake.

RESULTS

All infants were cobedded. The time awake during the nocturnal period decreased by almost 90 minutes from CA 3-6 weeks to CA 8-11 weeks. Sleep duration in the nocturnal period increased by almost 85 minutes, and the proportion of time with both infants sleeping rapidly increased in the same period. Maternal sleep duration during the period of both infants sleeping was positively correlated with CA.

CONCLUSION

This research revealed the transition of sleep behaviors in twin infants and their mothers in early infancy. Cobedding may facilitate more synchronized sleep states of twin infants.

Developing SENSES: Student experience of non-shared environment scales

Twin and adoption studies find that non-shared environmental (NSE) factors account for variance in most behavioural traits and offer an explanation for why genetically identical individuals differ. Using data from a qualitative hypothesis-generating study we designed a quantitative measure of pupils’ non-shared experiences at the end of formal compulsory education (SENSES: Student Experiences of Non-Shared Environment Scales). In Study 1 SENSES was administered to n = 117 16–19 year old twin pairs. Exploratory Factor Analysis yielded a 49-item 10 factor solution which explained 63% of the variance in responses. SENSES showed good internal consistency and convergent and divergent validity. In Study 2 this factor structure was confirmed with data from n = 926 twin pairs and external validity was demonstrated via significant correlations between 9 SENSES factors and both public examination performance and life satisfaction. These studies lend preliminary support to SENSES but further research is required to confirm its psychometric properties; to assess whether individual differences in SENSES are explained by NSE effects; and to explore whether SENSES explains variance in achievement and wellbeing.

Young adult mental health and functional outcomes among individuals with remitted, persistent and late-onset ADHD

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) is associated with mental health problems and functional impairment across many domains. However, how the longitudinal course of ADHD affects later functioning remains unclear.AimsWe aimed to disentangle how ADHD developmental patterns are associated with young adult functioning.

METHOD

The Environmental Risk (E-Risk) Longitudinal Twin Study is a population-based cohort of 2232 twins born in England and Wales in 1994-1995. We assessed ADHD in childhood at ages 5, 7, 10 and 12 years and in young adulthood at age 18 years. We examined three developmental patterns of ADHD from childhood to young adulthood - remitted, persistent and late-onset ADHD - and compared these groups with one another and with non-ADHD controls on functioning at age 18 years. We additionally tested whether group differences were attributable to childhood IQ, childhood conduct disorder or familial factors shared between twins.

RESULTS

Compared with individuals without ADHD, those with remitted ADHD showed poorer physical health and socioeconomic outcomes in young adulthood. Individuals with persistent or late-onset ADHD showed poorer functioning across all domains, including mental health, substance misuse, psychosocial, physical health and socioeconomic outcomes. Overall, these associations were not explained by childhood IQ, childhood conduct disorder or shared familial factors.

CONCLUSIONS

Long-term associations of childhood ADHD with adverse physical health and socioeconomic outcomes underscore the need for early intervention. Young adult ADHD showed stronger associations with poorer mental health, substance misuse and psychosocial outcomes, emphasising the importance of identifying and treating adults with ADHD.Declaration of interestNone.

A Co-Twin Control Study of the Relationship Between Adolescent Drinking and Adult Outcomes

OBJECTIVE

The effect of drinking during adolescence on adult functioning is a public health concern. A variety of mechanisms have been proposed where drinking in adolescence has an adverse impact on later outcomes; unfortunately, few studies have included methodologies that account for confounding influences that might link adolescent drinking with subsequent problems. To address this limitation, the current study used a co-twin control design, which uses members of twin pairs that differ from each other on their adolescent drinking.

METHOD

We used a prospective longitudinal sample drawn from the Minnesota Twin Family Study, consisting of 2,764 twins (1,434 female) assessed at regular follow-ups from age 17 to age 29. Adolescent drinking was defined by measures of early initiation of use and a measure of overall consumption at age 17. Adult outcomes included indicators of substance use, antisocial behavior, personality, socioeconomic status, and social functioning.

RESULTS

The co-twin control analyses suggested that many of the associations between adolescent drinking and later outcomes were largely influenced by genetic confounding. However, for the measure of adolescent alcohol consumption, results were consistent with a small causal impact of drinking on multiple domains of adult functioning. This pattern was less consistently observed for the measures of early initiation.

CONCLUSIONS

These results provide empirical justification for policies designed to alleviate long-term consequences associated with adolescent drinking by reducing the level of alcohol consumption in adolescence. In contrast, the evidence did not suggest that delaying drinking would have a broad impact on later-life adjustment.

A serious game for children with Attention Deficit Hyperactivity Disorder: Who benefits the most?

OBJECTIVE

The aim of the current study was to identify which subgroups of children with Attention Deficit Hyperactivity Disorder (ADHD) benefitted the most from playing a Serious Game (SG) intervention shown in a randomized trial to improve behavioral outcomes.

METHOD

Pre-intervention characteristics [i.e., gender, age, intellectual level of functioning, medication use, computer experience, ADHD subtype, severity of inattention problems, severity of hyperactivity/impulsivity problems, comorbid Oppositional Defiant Disorder (ODD) and Conduct Disorder (CD) symptoms] were explored as potential moderators in a Virtual Twins (VT) analysis to identify subgroups for whom the SG intervention was most effective. Primary outcome measures were parent-reported time management, planning/organizing and cooperation skills.

RESULTS

Two subgroups were identified. Girls (n = 26) were identified as the subgroup that was most likely to show greater improvements in planning/organizing skills as compared to the estimated treatment effect of the total group of participants. Furthermore, among the boys, those (n = 47) with lower baseline levels of hyperactivity and higher levels of CD symptoms showed more improvements in their planning/organizing skills when they played the SG intervention as compared to the estimated treatment effect of the total group of participants.

CONCLUSION

Using a VT analysis two subgroups of children with ADHD, girls, and boys with both higher levels of CD and lower levels of hyperactivity, were identified. These subgroups mostly benefit from playing the SG intervention developed to improve ADHD related behavioral problems. Our results imply that these subgroups have a higher chance of treatment success.

Shared genetic influences do not explain the association between parent-offspring relationship quality and offspring internalizing problems: results from a Children-of-Twins study

BACKGROUND

Associations between parenting and child outcomes are often interpreted as reflecting causal, social influences. However, such associations may be confounded by genes common to children and their biological parents. To the extent that these shared genes influence behaviours in both generations, a passive genetic mechanism may explain links between them. Here we aim to quantify the relative importance of passive genetic v. social mechanisms in the intergenerational association between parent-offspring relationship quality and offspring internalizing problems in adolescence.

METHODS

We used a Children-of-Twins (CoT) design with data from the parent-based Twin and Offspring Study of Sweden (TOSS) sample [909 adult twin pairs and their offspring; offspring mean age 15.75 (2.42) years], and the child-based Swedish Twin Study of CHild and Adolescent Development (TCHAD) sample [1120 adolescent twin pairs; mean age 13.67 (0.47) years]. A composite of parent-report measures (closeness, conflict, disagreements, expressions of affection) indexed parent-offspring relationship quality in TOSS, and offspring self-reported internalizing symptoms were assessed using the Child Behavior Checklist (CBCL) in both samples.

RESULTS

A social transmission mechanism explained the intergenerational association [r = 0.21 (0.16-0.25)] in our best-fitting model. A passive genetic transmission pathway was not found to be significant, indicating that parental genetic influences on parent-offspring relationship quality and offspring genetic influences on their internalizing problems were non-overlapping.

CONCLUSION

These results indicate that this intergenerational association is a product of social interactions between children and parents, within which bidirectional effects are highly plausible. Results from genetically informative studies of parenting-related effects should be used to help refine early parenting interventions aimed at reducing risk for psychopathology.

Genetic and Environmental Influences on Self-Control: Assessing Self-Control with the ASEBA Self-Control Scale

This study used a theoretically-derived set of items of the Achenbach System of Empirically Based Assessment to develop the Achenbach Self-Control Scale (ASCS) for 7-16 year olds. Using a large dataset of over 20,000 children, who are enrolled in the Netherlands Twin Register, we demonstrated the psychometric properties of the ASCS for parent-, self- and teacher-report by examining internal and criterion validity, and inter-rater and test-retest reliability. We found associations between the ASCS and measures of well-being, educational achievement, and substance use. Next, we applied the classical twin design to estimate the genetic and environmental contributions to self-control. Genetic influences accounted for 64-75% of the variance in self-control based on parent- and teacher-report (age 7-12), and for 47-49% of the variance in self-control based on self-report (age 12-16), with the remaining variance accounted by non-shared environmental influences. In conclusion, we developed a validated and accessible self-control scale, and show that genetic influences explain a majority of the individual differences in self-control across youth aged 7-16 years.

Stress reactivity links childhood trauma exposure to an admixture of depressive, anxiety, and psychosis symptoms

Childhood trauma exposure has been associated with a clinically relevant mixed phenotype of psychopathology composed of depressive, anxiety, and psychosis symptoms, across healthy and clinical samples. Altered stress-reactivity after exposure to childhood trauma may be a plausible underlying mechanism explaining this association. In a general population sample of female twins (T0 = 564; T1 = 483), associations between childhood trauma exposure and symptom profile (no symptoms, isolated symptoms, or a mixed phenotype) on the one hand, and daily life stress reactivity on the other were investigated. Daily life stress reactivity was measured using the Experience Sampling Method (ESM), and was defined as negative affect reactivity to minor daily life stressors. Individuals exposed to childhood trauma who reported a mixed phenotype of psychopathology showed a significant increase in emotional reactivity to daily life stress (activity and social stress), compared with trauma-exposed individuals without a mixed phenotype. In the trauma-exposed mixed phenotype group, increased emotional reactivity to event-stress predicted more severe symptoms at ± 14 month follow-up. This study found evidence that may link heightened emotional reactivity to stress in individuals with a trauma history to the risk for later comorbid psychopathology.

Psychoneurometric assessment of dispositional liabilities for suicidal behavior: phenotypic and etiological associations

BACKGROUND

Can core genetic liabilities for suicidal behavior be indexed using psychological and neural indicators combined? The current work addressed this question by examining phenotypic and genetic associations of two biobehavioral traits, threat sensitivity (THT) and disinhibition (DIS) - operationalized as psychoneurometric variables (i.e., composites of psychological-scale and neurophysiological measures) - with suicidal behaviors in a sample of adult twins.

METHODS

Participants were 444 identical and fraternal twins recruited from an urban community. THT was assessed using a psychological-scale measure of fear/fearlessness combined with physiological indicators of reactivity to aversive pictures, and DIS was assessed using scale measures of disinhibitory tendencies combined with indicators of brain response from lab performance tasks. Suicidality was assessed using items from structured interview and questionnaire protocols.

RESULTS

THT and DIS each contributed uniquely to prediction of suicidality when assessed psychoneurometrically (i.e., as composites of scale and neurophysiological indicators). In addition, these traits predicted suicidality interactively, with participants high on both reporting the greatest degree of suicidal behaviors. Biometric (twin-modeling) analyses revealed that a high percentage of the predictive association for each psychoneurometric trait (83% for THT, 68% for DIS) was attributable to genetic variance in common with suicidality.

CONCLUSIONS

Findings indicate that psychoneurometric assessments of biobehavioral traits index genetic liability for suicidal behavior, and as such, can serve as innovative targets for research on core biological processes contributing to severe psychopathology, including suicidal proclivities and actions.

Reduced frontal grey matter, life history of aggression, and underlying genetic influence

Physically healthy, adult, same-sexed twins (n = 287) from a population-based twin cohort underwent high-resolution magnetic resonance imaging (MRI) to identify fronto-limbic brain regions significantly associated with lifetime history of aggression. MRI scans used a 3D magnetization-prepared rapid acquisition gradient-echo (MP-RAGE) sequence, for voxel-based morphometry (VBM) and history of aggressive behavior was assessed using the Life History of Aggression measure. Aggression had modest, inverse associations with grey matter volume (GMV) in medial prefrontal cortex (mPFC, b = -0.20, se = 0.05, p < 0.001) and lateral prefrontal cortex (lPFC, b = -0.23, se = 0.06, p < 0.001). These associations were not confounded by other demographic, psychiatric, or personality factors. Biometrical twin analyses revealed significant heritabilities of 0.57 for GMV in the mPFC cluster and 0.36 for GMV in the lPFC cluster. Genetic factors accounted for the majority of the phenotypic correlations between aggression and mPFC GMV (85.3%) and between aggression and lPFC GMV (63.7%). Reduced GMV of prefrontal brain regions may be a neuronal characteristic of individuals with substantial histories of aggressive behavior regardless of psychiatric diagnosis. As such, these data suggest an anatomical correlate, with a possible genetic etiology, associated with functional deficits in social-emotional information processing.

Genetic and environmental influences on sociopolitical attitudes

A new paradigm has emerged in which both genetic and environmental factors are cited as possible influences on sociopolitical attitudes. Despite the increasing acceptance of this paradigm, several aspects of the approach remain underdeveloped. Specifically, limitations arise from a reliance on a twins-only design, and all previous studies have used self-reports only. There are also questions about the extent to which existing findings generalize cross-culturally. To address those issues, this study examined individual differences in liberalism/conservatism in a German sample that included twins, their parents, and their spouses and incorporated both self- and peer reports. The self-report findings from this extended twin family design were largely consistent with previous research that used that rater perspective, but they provided higher estimates of heritability, shared parental environmental influences, assortative mating, and genotype-environment correlation than the results from peer reports. The implications of these findings for the measurement and understanding of sociopolitical attitudes are explored.

Childhood behaviour problems show the greatest gap between DNA-based and twin heritability

For most complex traits, DNA-based heritability ('SNP heritability') is roughly half that of twin-based heritability. A previous report from the Twins Early Development Study suggested that this heritability gap is much greater for childhood behaviour problems than for other domains. If true, this finding is important because SNP heritability, not twin heritability, is the ceiling for genome-wide association studies. With twice the sample size as the previous report, we estimated SNP heritabilities (N up to 4653 unrelated individuals) and compared them with twin heritabilities from the same sample (N up to 4724 twin pairs) for diverse domains of childhood behaviour problems as rated by parents, teachers, and children themselves at ages 12 and 16. For 37 behaviour problem measures, the average twin heritability was 0.52, whereas the average SNP heritability was just 0.06. In contrast, results for cognitive and anthropometric traits were more typical (average twin and SNP heritabilities were 0.58 and 0.28, respectively). Future research should continue to investigate the reasons why SNP heritabilities for childhood behaviour problems are so low compared with twin estimates, and find ways to maximise SNP heritability for genome-wide association studies.

Observed Mother- and Father-Child Interaction Differences in Families with Medically Assisted Reproduction-Conceived Twins and Singletons

Increased medically assisted reproduction (MAR) use to treat infertility has resulted in a growing twin birth rate. Little is known about parent-child relationships for twin relative to singleton children in middle childhood. This study fills this gap by examining parent-child relationships in 57 families with eighty 6- to 12-year-old MAR twin and singleton children using observational data (warm and supportive communication, control, and hostility). Nested ANCOVAs indicate that while mothers exhibit similar interactional behaviors toward twins and singletons, fathers have less optimum behaviors toward twins relative to singletons. Twins displayed less engaged behavior with mothers and fathers relative to singletons. Given the vitality of parent-child relationships for family and child adjustment, future studies should examine determinants and outcomes of twin-singleton relationship differences to bolster twins' and their families' functioning.

Developmental Etiologies of Alcohol Use and Their Relations to Parent and Peer Influences Over Adolescence and Young Adulthood: A Genetically Informed Approach

BACKGROUND

Distinct changes in alcohol use etiologies occur during adolescence and young adulthood. Additionally, measured environments known to influence alcohol use such as peers and parenting practice can interact or be associated with this genetic influence. However, change in genetic and environmental influences over age, as well as how associations with measured environments change over age, is understudied.

METHODS

The National Longitudinal Study of Adolescent Health (Add Health) sibling subsample was used to examine data-driven biometric models of alcohol use over ages 13 to 27. Associations between friends' drinking, parental autonomy granting, and maternal closeness were also examined.

RESULTS

The best-fitting model included a 5-factor model consisting of early (ages 13 to 20) and overall (ages 13 to 27) additive genetic and unique environmental factors, as well as 1 overall common environment factor. The overall additive genetic factor and the early unique environment factor explained the preponderance of mean differences in the alcohol use over this portion of the life span. The most important factors explaining variance attributed to alcohol use changed over age. Additionally, friend use had the strongest associations with genetic and environmental factors at all ages, while parenting practices had almost no associations at any age.

CONCLUSIONS

These results supplement previous studies indicating changes in genetic and environmental influences in alcohol use over adolescence and adulthood. However, prior research suggesting that constraining exogenous predictors of genetic and environmental factors to have effects of the same magnitude across age overlooks the differential role of factors associated with alcohol use during adolescence. Consonant with previous research, friend use appears to have a more pervasive influence on alcohol use than parental influence during this age. Interventions and prevention programs geared toward reducing alcohol use in younger populations may benefit from focus on peer influence.

Test-retest reliability of the facial expression labeling task

Recognizing others' emotional expressions is vital for socioemotional development; impairments in this ability occur in several psychiatric disorders. Further study is needed to map the development of this ability and to evaluate its components as potential transdiagnostic endophenotypes. Before doing so, however, research is required to substantiate the test-retest reliability of scores of the face emotion identification tasks linked to developmental psychopathology. The current study estimated test-retest reliability of scores of one such task, the facial expression labeling task (FELT) among a sample of twin children (N = 157; ages 9-14). Participants completed the FELT at two visits two to five weeks apart. Participants discerned the emotion presented of faces depicting six emotions (i.e., happiness, anger, sadness, fear, surprise, and disgust) morphed with a neutral face to provide 10 levels of increasing emotional expressivity. The present study found strong test-retest reliability (Pearson r) of the FELT scores across all emotions. Results suggested that data from this task may be effectively analyzed using a latent growth curve model to estimate overall ability (i.e., intercept; r's = 0.76-0.85) and improvement as emotions become clearer (i.e., linear slope; r's = 0.69-0.83). Evidence of high test-retest reliability of this task's scores informs future developmental research and the potential identification of transdiagnostic endophenotypes for child psychopathology. (PsycINFO Database Record

What Twin Studies Tell Us About Brain Responses to Food Cues

PURPOSE OF REVIEW

Functional magnetic resonance imaging (fMRI) using visual food cues provides insight into brain regulation of appetite in humans. This review sought evidence for genetic determinants of these responses.

RECENT FINDINGS

Echoing behavioral studies of food cue responsiveness, twin study approaches detect significant inherited influences on brain response to food cues. Both polygenic (whole genome) factors and polymorphisms in single genes appear to impact appetite regulation, particularly in brain regions related to satiety perception. Furthermore, genetic confounding might underlie findings linking obesity to stereotypical response patterns on fMRI, i.e., associations with obesity may actually reflect underlying inherited susceptibilities rather than acquired levels of adiposity. Insights from twin studies show that genes powerfully influence brain regulation of appetite, emphasizing the role of inherited susceptibility factors in obesity risk. Future research to delineate mechanisms of inherited obesity risk could lead to novel or more targeted interventional approaches.

Testing the effects of adolescent alcohol use on adult conflict-related theta dynamics

OBJECTIVE

Adolescent alcohol use (AAU) is associated with brain anomalies, but less is known about long-term neurocognitive effects. Despite theoretical models linking AAU to diminished cognitive control, empirical work testing this relationship with specific cognitive control neural correlates (e.g., prefrontal theta-band EEG dynamics) remains scarce. A longitudinal twin design was used to test the hypothesis that greater AAU is associated with reduced conflict-related EEG theta-band dynamics in adulthood, and to examine the genetic/environmental etiology of this association.

METHODS

In a large (N=718) population-based prospective twin sample, AAU was assessed at ages 11/14/17. Twins completed a flanker task at age 29 to elicit EEG theta-band medial frontal cortex (MFC) power and medial-dorsal prefrontal cortex (MFC-dPFC) connectivity. Two complementary analytic methods (cotwin control analysis; biometric modeling) were used to disentangle the genetic/shared environmental risk towards AAU from possible alcohol exposure effects on theta dynamics.

RESULTS

AAU was negatively associated with adult cognitive control-related theta-band MFC power and MFC-dPFC functional connectivity. Genetic influences primarily underlie these associations.

CONCLUSIONS

Findings provide strong evidence that genetic factors underlie the comorbidity between AAU and diminished cognitive control-related theta dynamics in adulthood.

SIGNIFICANCE

Conflict-related theta-band dynamics appear to be candidate brain-based endophenotypes/mechanisms for AAU.

Parental involvement as an etiological moderator of middle childhood oppositional defiant disorder

The goal of this study was to investigate parental involvement as an etiologic moderator of oppositional defiant disorder (ODD) during middle childhood. Previous studies examining the influence of genetic and environmental factors on ODD have not considered whether and how these factors might vary by parental involvement. We thus conducted a series of "latent genetic by measured environmental" interaction analyses, in which measured parental involvement was allowed to moderate genetic, shared, and nonshared environmental influences on child ODD. Participants include 1,027 twin pairs (age ranged from 6 to 11 years old) from the Michigan State University Twin Registry. Results did indeed suggest that the etiology of ODD varies with maternal involvement, such that genetic influence on ODD became more prominent as maternal involvement decreased. However, these results were specific to children's perceptions of maternal involvement and did not extend to maternal perceptions of her involvement. There was no evidence that paternal involvement moderated the etiology of ODD, regardless of informant. The different results found in twins' and parents' data are consistent with those in previous research showing that children may have different perceptions from parents' about their family relationships and that this discrepancy needs to be taken into account in future research. (PsycINFO Database Record