Commentary: Why are children in the same family so different? Non-shared environment three decades later

Behavioral genetics of temporal framing: Heritability of time perspective and its common genetic bases with major personality traits

OBJECTIVE

The present study aimed to provide a seminal behavioral genetic analysis of time perspectives (TPs). Moreover, we intended to investigate the magnitude of genetic vs. environmental components of the well-established assocations between TPs and personality features.

BACKGROUND

Individual differences in temporal framing processes, referred to as TPs, are vital psychological and behavioral outcomes. Although proponents of TP theory emphasize mainly environmental origins of the tendencies to adopt certain TPs, research provides evidence for marked associations between the temporal dimensions and major personality traits that are known to be heritable. Hence, it was essential to empirically verify these claims.

METHOD

The article reports an analysis of genetic and environmental components of variance in TPs based on a study adopting a twin design, conducted on a sample of 393 pairs of twins (135 monozygotic and 258 dizygotic).

RESULTS

Multivariate Cholesky decomposition supported an EA model assuming impacts of both unshared environmental factors (E) and additive genetic factors (A) across all TP dimensions, suggesting that the effects of shared environment on TPs are plausibly negligible. Heritability indices of TPs ranged between 0.51 for Present-Fatalistic and 0.62 for Present-Hedonistic, suggesting that the majority of the variance in TPs stems from genetic influences. Substantial genetic correlations were found between TPs and the Big Five personality traits.

CONCLUSIONS

The findings provide further evidence for conceptualizing TPs as biologically based personality traits and challenge the claims that TP is mainly a product of culture, education, and personal experiences.

Variability in Neural Circuit Formation

The study of neural development is usually concerned with the question of how nervous systems get put together. Variation in these processes is usually of interest as a means of revealing these normative mechanisms. However, variation itself can be an object of study and is of interest from multiple angles. First, the nature of variation in both the processes and the outcomes of neural development is relevant to our understanding of how these processes and outcomes are encoded in the genome. Second, variation in the wiring of the brain in humans may underlie variation in all kinds of psychological and behavioral traits, as well as neurodevelopmental disorders. And third, genetic variation that affects circuit development provides the raw material for evolutionary change. Here, I examine these different aspects of variation in circuit development and consider what they may tell us about these larger questions.

Endophenotyping social cognition in the broader autism phenotype

Relatives of individuals with autism spectrum disorder (ASD) may display milder social traits of the broader autism phenotype (BAP) providing potential endophenotypic markers of genetic risk for ASD. We performed a case-control comparison to quantify social cognition and pragmatic language difficulties in the BAP (n = 25 cases; n = 33 controls) using the Faux Pas test (FPT) and the Goldman-Eisler Cartoon task. Using deep phenotyping we then examined patterns of inheritance of social cognition in two large multiplex families and the spectrum of performance in 32 additional families (159 members; n = 51 ASD, n = 87 BAP, n = 21 unaffected). BAP individuals showed significantly poorer FPT performance and reduced verbal fluency with the absence of a compression effect in social discourse compared to controls. In multiplex families, we observed reduced FPT performance in 89% of autistic family members, 63% of BAP relatives and 50% of unaffected relatives. Across all affected families, there was a graded spectrum of difficulties, with ASD individuals showing the most severe FPT difficulties, followed by the BAP and unaffected relatives compared to community controls. We conclude that relatives of probands show an inherited pattern of graded difficulties in social cognition with atypical faux pas detection in social discourse providing a novel candidate endophenotype for ASD.

Weighing poor immunometabolic health in relatives for severity of affective symptoms: A study of patients with depressive and anxiety disorders and their siblings

BACKGROUND

Affective (i.e. depressive and anxiety) disorders often co-occur with immunometabolic diseases and related biological pathways. Although many large population-based and meta-analytic studies have confirmed this link in community and clinical samples, studies in at-risk samples of siblings of persons with affective disorders are lacking. Furthermore, this somatic-mental co-occurrence may be partially explained by familial clustering of the conditions. First, we examined whether the association between a wide range of immunometabolic diseases and related biomarker based risk-profiles with psychological symptoms replicates in at-risk siblings of probands with affective disorders. Second, leveraging on a sibling-pair design, we disentangled and quantified the effect of probands' immunometabolic health on siblings' psychological symptoms and on the association between immunometabolic health and these symptoms in siblings.

METHODS

The sample included 636 participants (Mage = 49.7; 62.4% female) from 256 families, each including a proband with lifetime depressive and/or anxiety disorders and at least one of their sibling(s) (N = 380 proband-sibling pairs). Immunometabolic health included cardiometabolic and inflammatory diseases, body mass index (BMI), and composite metabolic (based on the five metabolic syndrome components) and inflammatory (based on interleukin-6 and C-reactive protein) biomarker indices. Overall affective symptoms and specific atypical, energy-related depressive symptoms were derived from self-report questionnaires. Mixed-effects analyses were used to model familial clustering.

RESULTS

In siblings, inflammatory disease (γ = 0.25, p = 0.013), higher BMI (γ = 0.10, p = 0.033) and metabolic index (γ = 0.28, p < 0.001) were associated with higher affective symptoms, with stronger associations for atypical, energy-related depressive symptoms (additionally associated with cardiometabolic disease; γ = 0.56, p = 0.048). Immunometabolic health in probands was not independently associated with psychological symptoms in siblings nor did it moderate the association between immunometabolic health and psychological symptoms estimated in siblings.

CONCLUSIONS

Our findings demonstrate that the link between later life immunometabolic health and psychological symptoms is consistently present also in adult siblings at high risk for affective disorders. Familial clustering did not appear to have a substantial impact on this association. Instead, individual lifestyle, rather than familial factors, may have a relatively higher impact in the clustering of later life immunometabolic conditions with psychological symptoms in at-risk adult individuals. Furthermore, results highlighted the importance of focusing on specific depression profiles when investigating the overlap with immunometabolic health.

Weighing psychosocial factors in relatives for the risk of psychopathology: a study of patients with depressive and anxiety disorders and their siblings

PURPOSE

Siblings of probands with depressive and anxiety disorders are at increased risk for psychopathology, but little is known about how risk factors operate within families to increase psychopathology for siblings. We examined the additional impact of psychosocial risk factors in probands-on top of or in combination with those in siblings-on depressive/anxious psychopathology in siblings.

METHODS

The sample included 636 participants (Mage = 49.7; 62.4% female) from 256 families, each including a proband with lifetime depressive and/or anxiety disorders and their sibling(s) (N = 380 proband-sibling pairs). Sixteen psychosocial risk factors were tested. In siblings, depressive and anxiety disorders were determined with standardized psychiatric interviews; symptom severity was measured using self-report questionnaires. Analyses were performed with mixed-effects models accounting for familial structure.

RESULTS

In siblings, various psychosocial risk factors (female gender, low income, childhood trauma, poor parental bonding, being single, smoking, hazardous alcohol use) were associated with higher symptomatology and likelihood of disorder. The presence of the same risk factor in probands was independently associated (low income, being single) with higher symptomatology in siblings or moderated (low education, childhood trauma, hazardous alcohol use)-by reducing its strength-the association between the risk factor and symptomatology in siblings. There was no additional impact of risk factors in probands on likelihood of disorder in siblings.

CONCLUSION

Our findings demonstrate the importance of weighing psychosocial risk factors within a family context, as it may provide relevant information on the risk of affective psychopathology for individuals.

Explaining the influence of non-shared environment (NSE) on symptoms of behaviour problems from preschool to adulthood: mind the missing NSE gap

BACKGROUND

Individual differences in symptoms of behaviour problems in childhood and adolescence are not primarily due to nature or nurture - another substantial source of variance is non-shared environment (NSE). However, few specific environmental factors have been found to account for these NSE estimates. This creates a 'missing NSE' gap analogous to the 'missing heritability' gap, which refers to the shortfall in identifying DNA differences responsible for heritability. We assessed the extent to which variance in behaviour problem symptoms during the first two decades of life can be accounted for by measured NSE effects after controlling for genetics and shared environment.

METHODS

The sample included 4,039 pairs of twins in the Twins Early Development Study whose environments and symptoms of behaviour problems were assessed in preschool, childhood, adolescence and early adulthood via parent, teacher and self-reports. Twin-specific environments were assessed via parent-reports, including early life adversity, parental feelings, parental discipline and classroom environment. Multivariate longitudinal twin model-fitting was employed to estimate the variance in behaviour problem symptoms at each age that could be predicted by environmental measures at the previous age.

RESULTS

On average across childhood, adolescence and adulthood, parent-rated NSE composite measures accounted for 3.4% of the reliable NSE variance (1.0% of the total variance) in parent-rated, symptoms of behaviour problems, 0.5% (0.1%) in teacher-rated symptoms and 0.9% (0.5%) in self-rated symptoms after controlling for genetics, shared environment and error of measurement. Cumulatively across development, our parent-rated NSE measures in preschool, childhood and adolescence predicted 4.7% of the NSE variance (2.0% of the total variance) in parent-rated and 0.3% (0.2%) in self-rated behaviour problem symptoms in adulthood.

CONCLUSIONS

The missing NSE gap between variance explained by measured environments and total NSE variance is large. Home and classroom environments are more likely to influence behaviour problem symptoms via genetics than via NSE.

Sexual-orientation differences in risk of health-related impaired ability to work and to remain in the paid workforce: a prospective population-based twin study

BACKGROUND

Studies consistently show an increased risk of poor health among sexual minorities (i.e., those identifying as lesbian, gay, bisexual [LGB] or other non-heterosexuals individuals), as compared to those identifying as heterosexual. It is largely unknown whether the increased risk of mental and physical health problems among sexual minorities is also reflected in an increased risk of health-related impaired ability to work, in terms of sickness absence (SA) and disability pension (DP), or successfully remain in the paid workforce. This study made use of a large sample of Swedish twins with self-reported information about sexual behavior in young adulthood to examine sexual orientation difference in SA and DP during a 12-year follow-up period.

METHOD

Data from the Swedish Twin project of Disability pension and Sickness absence (STODS), including Swedish twins born 1959-1985 was used (N = 17,539; n = 1,238 sexual minority). Self-report survey data on sexual behavior was linked to information about SA and DP benefits from the MicroData for Analysis of the Social Insurance database (MiDAS), the National Social Insurance Agency. Sexual orientation differences in SA and DP between 2006 and 2018 was analyzed, as well as, the influence of sociodemographic, social stress exposure (i.e., victimization, discrimination), mental health treatment, and family confounding on these differences.

RESULTS

Compared to heterosexuals, sexual minorities were more likely to having experienced SA and having been granted DP. The odds were highest for DP, where sexual minorities were 58% more likely to having been granted DP compared to heterosexuals. The higher odds for SA due to any diagnosis could largely be explained by sociodemographic factors. The higher odds of SA due to mental diagnosis could partially be explained by increased risk of being exposed to discrimination and victimization, and partially by having received treatment with antidepressant medication. The higher odds of being granted DP could also partially be explain by increased risk of being exposed to social stress and treatment with antidepressant medication.

CONCLUSION

To our knowledge, this is the first study to report on sexual orientation differences in risk of SA and DP in a population-based sample. We found higher period prevalence of both SA and DP among sexual minorities as compared to heterosexuals. The higher odds of SA and DP could partially or fully be explained by sexual orientation differences in sociodemographic factors, exposure to social stress, and antidepressant treatment for depression. Future studies can extend these findings by continuing to investigate risk factors for SA and DP among sexual minorities and how such factors can be reduced.

Celebrating a Century of Research in Behavioral Genetics

A century after the first twin and adoption studies of behavior in the 1920s, this review looks back on the journey and celebrates milestones in behavioral genetic research. After a whistle-stop tour of early quantitative genetic research and the parallel journey of molecular genetics, the travelogue focuses on the last fifty years. Just as quantitative genetic discoveries were beginning to slow down in the 1990s, molecular genetics made it possible to assess DNA variation directly. From a rocky start with candidate gene association research, by 2005 the technological advance of DNA microarrays enabled genome-wide association studies, which have successfully identified some of the DNA variants that contribute to the ubiquitous heritability of behavioral traits. The ability to aggregate the effects of thousands of DNA variants in polygenic scores has created a DNA revolution in the behavioral sciences by making it possible to use DNA to predict individual differences in behavior from early in life.

Genetic variance in conscientiousness relates to youth psychopathology beyond executive functions

Because deficits in self-regulation (SR) are core features of many diverse psychological disorders, SR may constitute one of many dimensions that underlie shared variance across diagnostic boundaries (e.g., the p factor, a dimension reflecting shared variance across multiple psychological disorders). SR definitions encompass constructs mapping onto different theoretical traditions and different measurement approaches, however. Two SR operationalizations, executive functioning and conscientiousness, are often used interchangeably despite their low empirical associations-a "jingle" fallacy that pervades much of the research on SR-psychopathology relationships. In a population-based sample of 1,219 twins and multiples from the Texas Twin Project (Mage = 10.60, SDage = 1.76), with a comprehensive battery of measures, we aimed to clarify how these often-muddled aspects of SR relate to individual differences in psychopathology, and whether links between them are accounted for by overlapping genetic and environmental factors. The p factor and an Attention Problems-specific factor were associated with lower executive functioning and conscientiousness. Executive functioning shared a small amount of genetic variance with p above and beyond conscientiousness, whereas conscientiousness shared substantial genetic variance with p independently of genetic variance accounted for by executive functioning. Conversely, the Attention Problems-specific factor was strongly genetically associated with executive functioning independently of genetic variance accounted for by conscientiousness. Results support the notion that SR and psychopathology, broadly conceived, may exist on overlapping spectra, but this overlap varies across conceptualizations of SR and the level of specificity at which psychopathology is assessed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

On the importance of parenting in externalizing disorders: an evaluation of indirect genetic effects in families

BACKGROUND

Theoretical models of the development of childhood externalizing disorders emphasize the role of parents. Empirical studies have not been able to identify specific aspects of parental behaviors explaining a considerable proportion of the observed individual differences in externalizing problems. The problem is complicated by the contribution of genetic factors to externalizing problems, as parents provide both genes and environments to their children. We studied the joint contributions of direct genetic effects of children and the indirect genetic effects of parents through the environment on externalizing problems.

METHODS

The study used genome-wide single nucleotide polymorphism data from 9,675 parent-offspring trios participating in the Norwegian Mother Father and child cohort study. Based on genomic relatedness matrices, we estimated the contribution of direct genetic effects and indirect maternal and paternal genetic effects on ADHD, conduct and disruptive behaviors at 8 years of age.

RESULTS

Models including indirect parental genetic effects were preferred for the ADHD symptoms of inattention and hyperactivity, and conduct problems, but not oppositional defiant behaviors. Direct genetic effects accounted for 11% to 24% of the variance, whereas indirect parental genetic effects accounted for 0% to 16% in ADHD symptoms and conduct problems. The correlation between direct and indirect genetic effects, or gene-environment correlations, decreased the variance with 16% and 13% for conduct and inattention problems, and increased the variance with 6% for hyperactivity problems.

CONCLUSIONS

This study provides empirical support to the notion that parents have a significant role in the development of childhood externalizing behaviors. The parental contribution to decrease in variation of inattention and conduct problems by gene-environment correlations would limit the number of children reaching clinical ranges in symptoms. Not accounting for indirect parental genetic effects can lead to both positive and negative bias when identifying genetic variants for childhood externalizing behaviors.

Gene-environment interaction using polygenic scores: Do polygenic scores for psychopathology moderate predictions from environmental risk to behavior problems?

The DNA revolution has energized research on interactions between genes and environments (GxE) by creating indices of G (polygenic scores) that are powerful predictors of behavioral traits. Here, we test the extent to which polygenic scores for attention-deficit/hyperactivity disorder and neuroticism moderate associations between parent reports of their children's environmental risk (E) at ages 3 and 4 and teacher ratings of behavior problems (hyperactivity/inattention, conduct problems, emotional symptoms, and peer relationship problems) at ages 7, 9 and 12. The sampling frame included up to 6687 twins from the Twins Early Development Study. Our analyses focused on relative effect sizes of G, E and GxE in predicting behavior problems. G, E and GxE predicted up to 2%, 2% and 0.4%, respectively, of the variance in externalizing behavior problems (hyperactivity/inattention and conduct problems) across ages 7, 9 and 12, with no clear developmental trends. G and E predictions of emotional symptoms and peer relationship problems were weaker. A quarter (12 of 48) of our tests of GxE were nominally significant (p = .05). Increasing the predictive power of G and E would enhance the search for GxE.

Heritability of Psychological Traits and Developmental Milestones in Infancy: A Systematic Review and Meta-analysis

IMPORTANCE

Although infancy is the most rapid period of postnatal growth and development, factors associated with variation in infant traits are not well understood.

OBJECTIVE

To synthesize the large twin study literature partitioning phenotypic variance in psychological traits and developmental milestones in infancy into estimates of heritability and shared and nonshared environment.

DATA SOURCES

PubMed, PsycINFO, and references of included publications were searched up to February 11, 2021.

STUDY SELECTION

Peer-reviewed publications using the classical twin design to study psychological traits and developmental milestones from birth to 2 years old were included.

DATA EXTRACTION AND SYNTHESIS

Data were extracted in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and categorized using the International Classification of Functioning, Disability and Health: Children and Youth Version. Data were pooled in 3-level random effects models, incorporating within-cohort variance in outcome measurement and between-cohort variance. Data were analyzed from March 2021 through September 2021.

MAIN OUTCOMES AND MEASURES

The primary outcomes were monozygotic and dizygotic twin correlations. These were used to calculate genetic and shared and nonshared environment estimates.

RESULTS

Among 139 publications that were systematically retrieved, data were available on 79 044 twin pairs (31 053 monozygotic and 47 991 dizygotic pairs), 52 independent samples, and 21 countries. Meta-analyses were conducted on psychological traits and developmental milestones from 106 publications organized into 10 categories of functioning, disability, and health. Moderate to high genetic estimates for 8 categories were found, the highest of which was psychomotor functions (pooled h2, 0.59; 95% CI, 0.25-0.79; P < .001). Several categories of traits had substantial shared environment estimates, the highest being mental functions of language (pooled c2, 0.59; 95% CI, 0.24-0.86; P = .001). All examined categories of traits had moderate or high nonshared environment estimates, the highest of which were emotional functions (pooled e2, 0.42; 95% CI, 0.33-0.50; P < .001) and family relationships (pooled e2, 0.42; 95% CI, 0.30-0.55; P < .001).

CONCLUSIONS AND RELEVANCE

These findings may be an important source of information to guide future gene discovery research, public perspectives on nature and nurture, and clinical insights into the degree to which family history and environments may estimate major domains of infant functioning, disability, and health in psychological traits and developmental milestones.

Pre-, Peri-, and Neonatal Factors Associated with Autism Spectrum Disorder: Results of a Lebanese Case-control Study

OBJECTIVE

The prevalence of autism spectrum disorder (ASD) in Lebanon is higher than what is reported by the World Health Organization (WHO), leading to the thought that the Lebanese population has some specific risk factors for ASD. Therefore, it is important to conduct more robust studies on this population. We conducted this study to identify pre-, peri-, and neonatal risk factors for ASD. Our ultimate goal was to detect and change some modifiable risk factors, thus reducing the incidence of ASD.

DESIGN

A case-control study was conducted using a random proportional sample of Lebanese children with ASD to explore whether risk factors, such as family history, pregnancy (including all medication and substances taken during pregnancy and infection history), gestational age, delivery, birth milestones, and the neonate's condition at birth could be associated with a higher prevalence of ASD. The local ethical committee approved the study (USJ-2016-91), and all parents gave their written consent.

RESULTS

A total of 66 children with ASD and 66 controls were included. The results of the multivariable analysis showed that a higher gestational weight gain (adjusted odds ratio [ORa]: 1.11) was significantly associated with higher odds of autism, whereas female sex (ORa: 0.13) and higher number of weeks of gestation (ORa: 0.76) were significantly associated with lower odds of autism.

CONCLUSION

Such results are of great relevance, since many of the identified factors herein could be avoidable or modifiable, suggesting the need for implementing timely and appropriate public health strategies for disease prevention in pregnant women that could reduce ASD.

Specialised minds: extending adaptive explanations of personality to the evolution of psychopathology

Traditional evolutionary theory invoked natural and sexual selection to explain species- and sex-typical traits. However, some heritable inter-individual variability in behaviour and psychology - personality - is probably adaptive. Here we extend this insight to common psychopathological traits. Reviewing key findings from three background areas of importance - theoretical models, non-human personality and evolved human social dynamics - we propose that a combination of social niche specialisation, negative frequency-dependency, balancing selection and adaptive developmental plasticity should explain adaptation for individual differences in psychology - 'specialised minds' - explaining some variance in personality and psychopathology trait dimensions, which share various characteristics. We suggest that anthropological research of behavioural differences should be extended past broad demographic factors (age and sex) to include individual specialisations. As a first step towards grounding psychopathology in ancestral social structure, we propose a minimum plausible prevalence, given likely ancestral group sizes, for negatively frequency-dependent phenotypes to be maintained as specialised tails of adaptive distributions - below the calculated prevalence, specialisation is highly unlikely. For instance, chronic highly debilitating forms of autism or schizophrenia are too rare for such explanations, whereas attention-deficit-hyperactivity disorder and broad autism phenotypes are common enough to have existed in most hunter-gatherer bands, making adaptive explanations more plausible.

The aetiology of educational attainment: A nuclear twin family study into the genetic and environmental influences on school leaving certificates

BACKGROUND

Educational attainment is connected to many important life outcomes, and the previous research has already focused on identifying its genetic and environmental components. However, most of these studies used twin data only and did not incorporate information from other family members. Twin studies typically decompose the phenotypic variance into genetic, shared, and unique environment components. In this study design, the shared environment component encompasses the influence of parents and the shared environments of twins and siblings independent of parents (e.g., teachers, schools, and peers). The classical twin design (CTD) conflates these influences as part of the shared environment. This shortcoming can be overcome using the nuclear twin family design (NTFD), which enables separation of the parental and shared twin/sibling environmental components.

AIMS

The aim of this study was to broaden the understanding of the aetiology of educational attainment using the nuclear twin family design to provide a detailed account of the genetic and environmental effects on the type of school leaving certificate.

SAMPLE

The data of 1,048 monozygotic and 916 dizygotic same-sex twins, their biological parents, and non-twin full biological siblings of the German project TwinLife were used in the nuclear twin family design.

METHODS

Structural equation modelling (SEM) techniques were used to analyse the variance-covariance patterns of the ordinal outcome variable.

RESULTS

Genetic influences were found to make up around 60% of variance, whilst environmental influences shared by all siblings, educational influences shared by the twins only, and non-shared environmental influences explained the remaining variance in equal amounts. Environmental transmission from parent to offspring was found to be negligible.

CONCLUSION

Through its advanced design, our study extends the previous work enabling more detailed and robust estimations of sources of variance and contributes to a better understanding of the complex aetiology of educational attainment.

Familial resemblance in mental health symptoms, social and cognitive vulnerability, and personality: A study of patients with depressive and anxiety disorders and their siblings

BACKGROUND

Investigating siblings of probands with affective disorders enables the identification of psychopathology-related risk features. Leveraging data from an older adult sample, as compared to most previous sibling studies, enabled us to study more definitive clinical profiling across the lifespan. We examined prevalence of depressive/anxiety disorders in siblings, proband-sibling resemblance in psychopathology-related features, and whether unaffected siblings showed higher levels of these features than healthy controls.

METHODS

The sample (N=929; M_age=50.6) consisted of 256 probands with lifetime depressive and/or anxiety disorders, their 380 siblings, and 293 healthy controls without affected relatives. Fifteen psychopathology-related features were investigated across four domains: mental health symptoms, social vulnerabilities, cognitive vulnerabilities, and personality.

RESULTS

Lifetime disorders were present in 50.3% of siblings. Prevalence was 2-3 times higher than Dutch population frequencies. We found small to medium probandsibling resemblance across psychopathology-related features (ρ=0.10-0.32). Unaffected siblings reported poorer interpersonal functioning and more negative life events, childhood trauma, and rumination than healthy controls.

LIMITATIONS

Due to the cross-sectional study design, the directionality of effects cannot be determined. No inferences can be made about potential differences in familial resemblance in psychopathology-related features between high- and low-risk families.

CONCLUSIONS

Siblings of probands with affective disorders are at higher risk for depressive/anxiety disorders. Even when unaffected, still show higher psychosocial vulnerability than healthy controls. Nevertheless, the only modest proband-sibling resemblance across psychopathology-related features suggests that individual mechanisms differentiate clinical trajectories across the lifespan. Identification of these mechanisms is crucial to improve resilience in subjects with familial risk.

It is a family affair: individual experiences and sibling exposure to emotional, physical and sexual abuse and the impact on adult depressive symptoms

BACKGROUND

Childhood abuse and neglect often occurs within families and can have a large influence on mental well-being across the lifespan. However, the sibling concordance of emotional abuse and neglect (i.e. together referred to as emotional maltreatment; EM), physical abuse (PA) and sexual abuse (SA) and the long-term impact on the context of siblings' maltreatment experiences are unclear. To examine the influence of EM, PA and SA on adult depressive symptoms within the family framework we differentiate between (a) the family-wide (mean level of all siblings) effects and (b) the individual deviation from the mean family level of maltreatment.

METHODS

The sample (N = 636) consists of 256 families, including at least one lifetime depressed or anxious individual and their siblings. Multilevel modeling was used to examine the family-wide and relative individual effects of childhood maltreatment (CM).

RESULTS

(a) Siblings showed most similarity in their reports of EM followed by PA. SA was mostly reported by one person within a family. In line with these observations, the mean family levels of EM and PA, but not SA, were associated with more depressive symptoms. In addition, (b) depression levels were more elevated in individuals reporting more EM than the family mean.

CONCLUSIONS

Particularly in the case of more visible forms of CM, siblings' experiences of EM and PA are associated with the elevated levels of adult depressive symptoms. Findings implicate that in addition to individual maltreatment experiences, the context of siblings' experiences is another crucial risk factor for an individuals' adult depressive symptomatology.

Vital personality scores and healthy aging: Life-course associations and familial transmission

OBJECTIVES

Personality traits are linked with healthy aging, but it is not clear how these associations come to manifest across the life-course and across generations. To study this question, we tested a series of hypotheses about (a) personality-trait prediction of markers of healthy aging across the life-course, (b) developmental origins, stability and change of links between personality and healthy aging across time, and (c) intergenerational transmission of links between personality and healthy aging. For our analyses we used a measure that aggregates the contributions of Big 5 personality traits to healthy aging: a "vital personality" score.

METHODS

Data came from two population-based longitudinal cohort studies, one based in New Zealand and the other in the UK, comprising over 6000 study members across two generations, and spanning an age range from birth to late life.

RESULTS

Our analyses revealed three main findings: first, individuals with higher vital personality scores engaged in fewer health-risk behaviors, aged slower, and lived longer. Second, individuals' vital personality scores were preceded by differences in early-life temperament and were relatively stable across adulthood, but also increased from young adulthood to midlife. Third, individuals with higher vital personality scores had children with similarly vital partners, promoted healthier behaviors in their children, and had children who grew up to have more vital personality scores themselves, for genetic and environmental reasons.

CONCLUSION

Our study shows how the health benefits associated with personality accrue throughout the life-course and across generations.

Noncitizen Children Face Higher Health Harms Compared With Their Siblings Who Have US Citizen Status

Immigrant children in the US have very limited health insurance coverage and health care access. Immigration status is not static: Census data show that the majority of census respondents who enter as noncitizen children eventually become citizens. Eligibility restrictions that prevent noncitizen children from being publicly insured can contribute to their experiencing poorer health and higher medical costs in their adult lives. We isolate the impact of lack of citizenship from socioeconomic factors by comparing citizen and noncitizen siblings living in mixed-status families, using fixed-effects models to net out socioeconomic factors shared within families. Lacking citizenship increased a child's risk of being uninsured and lowered by 26 percentage points the chances that they would have Medicaid or Children's Health Insurance Program coverage. Noncitizen children had significantly more delays in needed medical care because of cost, primarily mediated by the lack of insurance coverage. The US should reexamine policies that exclude noncitizen children from public health insurance programs.

Origins of human disease: the chrono-epigenetic perspective

Epigenetics has enriched human disease studies by adding new interpretations to disease features that cannot be explained by genetic and environmental factors. However, identifying causal mechanisms of epigenetic origin has been challenging. New opportunities have risen from recent findings in intra-individual and cyclical epigenetic variation, which includes circadian epigenetic oscillations. Cytosine modifications display deterministic temporal rhythms, which may drive ageing and complex disease. Temporality in the epigenome, or the 'chrono' dimension, may help the integration of epigenetic, environmental and genetic disease studies, and reconcile several disparities stemming from the arbitrarily delimited research fields. The ultimate goal of chrono-epigenetics is to predict disease risk, age of onset and disease dynamics from within individual-specific temporal dynamics of epigenomes.

Quantitative and Qualitative Perspectives of Siblings of Children With Cochlear Implants

Purpose The sibling relationship teaches children to navigate social interactions with their peers. However, the presence of an exceptionality, such as hearing loss, in one child can affect the dynamic of this relationship. This article examines quantitative and qualitative effects of having a brother or sister with a cochlear implant (CI) on siblings with typical hearing (TH) to determine how children with TH perceive their sibling with a CI and how having a CI user in the family affects the sibling's activities, emotions, and parental attention. Method Participants include 36 siblings with TH (M _age = 11.6 years) of CI users (M _age = 11.9 years) who completed quantitative measures of their perspectives of their brother/sister with CIs and the effect of hearing loss on themselves. Siblings with TH also could express their opinions via open-ended prompts. Results Overall, siblings with TH express positive perspectives of their brother/sister with CIs and report having a CI user in the family does not affect them much, particularly if the CI user has adequate communication skills. Responses to both quantitative and qualitative items converge on the close relationship between siblings but diverge relative to differential attention from parents (i.e., open-ended responses suggest parents spend more time with the CI user than the sibling with TH). Additionally, siblings acknowledge the presence of social communication deficits of the CI user in real-world situations. Conclusion This nuanced look at relationships among the parent, CI user, and sibling with TH highlights the importance of understanding the family system when working with children with hearing loss.

The Analytic Identification of Variance Component Models Common to Behavior Genetics

Many behavior genetics models follow the same general structure. We describe this general structure and analytically derive simple criteria for its identification. In particular, we find that variance components can be uniquely estimated whenever the relatedness matrices that define the components are linearly independent (i.e., not confounded). Thus, we emphasize determining which variance components can be identified given a set of genetic and environmental relationships, rather than the estimation procedures. We validate the identification criteria with several well-known models, and further apply them to several less common models. The first model distinguishes child-rearing environment from extended family environment. The second model adds a gene-by-common-environment interaction term in sets of twins reared apart and together. The third model separates measured-genomic relatedness from the scanner site variation in a hypothetical functional magnetic resonance imaging study. The computationally easy analytic identification criteria allow researchers to quickly address model identification issues and define novel variance components, facilitating the development of new research questions.

Heritability of brain resilience to perturbation in humans

Resilience is the capacity of complex systems to persist in the face of external perturbations and retain their functional properties and performance. In the present study, we investigated how individual variations in brain resilience, which might influence response to stress, aging and disease, are influenced by genetics and/or the environment, with potential implications for the implementation of resilience-boosting interventions. Resilience estimates were derived from in silico lesioning of either brain regions or functional connections constituting the connectome of healthy individuals belonging to two different large and unique datasets of twins, specifically: 463 individual twins from the Human Connectome Project and 453 individual twins from the Colorado Longitudinal Twin Study. As has been reported previously, moderate heritability was found for several topological indexes of brain efficiency and modularity. Importantly, evidence of heritability was found for resilience measures based on removal of brain connections rather than specific single regions, suggesting that genetic influences on resilience are preferentially directed toward region-to-region communication rather than local brain activity. Specifically, the strongest genetic influence was observed for moderately weak, long-range connections between a specific subset of functional brain networks: the Default Mode, Visual and Sensorimotor networks. These findings may help identify a link between brain resilience and network-level alterations observed in neurological and psychiatric diseases, as well as inform future studies investigating brain shielding interventions against physiological and pathological perturbations.

Is any but a tiny fraction of handedness variance likely to be due to the external environment?

Non-shared environmental variance (NSEV) accounts for 76% of variance in genetic modelling of handedness. However, it is very misleading to suggest that NSEV, "highlights the importance of non-genetic factors for the ontogenesis of hemispheric asymmetries". NSEV is poorly named, is calculated only by subtraction, and provides no direct evidence for environmental effects in the sense of the external environment. Miller suggested that it would be better named as "residual effect". Mitchell has suggested that much or indeed most of NSEV is "developmental variance" and should be included under the heading of nature rather than nurture, and in handedness, "largely reflect[s] the outcome of randomness in brain development". Overall only a very small proportion of NSEV in handedness is likely to be related to external environmental factors in the usual sense of the term.

Why some siblings thrive whereas others struggle: A within-family study on recollections of childhood parental bonding and current adult depressive and anxiety symptoms

BACKGROUND

Brothers and sisters growing up together share a large proportion of their genes and rearing environment. However, some siblings thrive whereas others struggle. This study investigated family-wide childhood bonding experiences with mother and father, in addition to individual-specific recollections, in relation to current depressive and anxiety symptom levels in adulthood. We examined whether extraversion and internal locus of control (iLoC) had a protective effect in this.

METHODS

The sample consisted of 256 families with at least one lifetime depressed or anxious person (N = 596; ages 20-78). Multilevel modeling with cross-level interactions was used.

RESULTS

Adult siblings showed moderate to high agreement in their childhood parental bonding (PB) recollections. Over-and-above the association between individual-specific recollections of PB and adult internalizing symptoms, family-wide poor PB was additionally linked to elevated symptom levels. Within families characterized by poor maternal bonding persons with an iLoC were relatively less anxious (but not less depressed), whereas extraversion was not protective in this context.

LIMITATION

Although evidence exists that poor childhood PB has an impact on (adult) psychopathology, causality cannot be determined and possible recall bias of PB should be noted. Moreover, next to their moderating effects, extraversion and LoC may also act as mediators.

CONCLUSIONS

Our findings extend prior work by demonstrating the importance of siblings' childhood PB experiences next to a person's own recollections when investigating adult internalizing symptoms, while also elucidating individual differences within families.

Individual Differences in Intrinsic Brain Networks Predict Symptom Severity in Autism Spectrum Disorders

The neurobiology of heterogeneous neurodevelopmental disorders such as Autism Spectrum Disorders (ASD) is still unknown. We hypothesized that differences in subject-level properties of intrinsic brain networks were important features that could predict individual variation in ASD symptom severity. We matched cases and controls from a large multicohort ASD dataset (ABIDE-II) on age, sex, IQ, and image acquisition site. Subjects were matched at the individual level (rather than at group level) to improve homogeneity within matched case-control pairs (ASD: n = 100, mean age = 11.43 years, IQ = 110.58; controls: n = 100, mean age = 11.43 years, IQ = 110.70). Using task-free functional magnetic resonance imaging, we extracted intrinsic functional brain networks using projective non-negative matrix factorization. Intrapair differences in strength in subnetworks related to the salience network (SN) and the occipital-temporal face perception network were robustly associated with individual differences in social impairment severity (T = 2.206, P = 0.0301). Findings were further replicated and validated in an independent validation cohort of monozygotic twins (n = 12; 3 pairs concordant and 3 pairs discordant for ASD). Individual differences in the SN and face-perception network are centrally implicated in the neural mechanisms of social deficits related to ASD.

Intergenerational transmission: Theoretical and methodological issues and an introduction to four Dutch cohorts

Behaviors, traits and characteristics are transmitted from parents to offspring because of complex genetic and non-genetic processes. We review genetic and non-genetic mechanisms of intergenerational transmission of psychopathology and parenting and focus on recent methodological advances in disentangling genetic and non-genetic factors. In light of this review, we propose that future studies on intergenerational transmission should aim to disentangle genetic and non-genetic transmission, take a long-term longitudinal perspective, and focus on paternal and maternal intergenerational transmission. We present four large longitudinal cohort studies within the Consortium on Individual Development, which together address many of these methodological challenges. These four cohort studies aim to examine the extent to which genetic and non-genetic transmission from the parental generation shapes parenting behavior and psychopathology in the next generation, as well as the extent to which self-regulation and social competence mediate this transmission. Conjointly, these four cohorts provide a comprehensive approach to the study of intergenerational transmission.

Estimating the Heritability of Experiencing Child Maltreatment in an Extended Family Design

Child-driven genetic factors can contribute to negative parenting and may increase the risk of being maltreated. Experiencing childhood maltreatment may be partly heritable, but results of twin studies are mixed. In the current study, we used a cross-sectional extended family design to estimate genetic and environmental effects on experiencing child maltreatment. The sample consisted of 395 individuals (225 women; M_age = 38.85 years, range_age = 7-88 years) from 63 families with two or three participating generations. Participants were oversampled for experienced maltreatment. Self-reported experienced child maltreatment was measured using a questionnaire assessing physical and emotional abuse, and physical and emotional neglect. All maltreatment phenotypes were partly heritable with percentages for h² ranging from 30% (SE = 13%) for neglect to 62% (SE = 19%) for severe physical abuse. Common environmental effects (c²) explained a statistically significant proportion of variance for all phenotypes except for the experience of severe physical abuse (c² = 9%, SE = 13%, p = .26). The genetic correlation between abuse and neglect was ρ_g = .73 (p = .02). Common environmental variance increased as socioeconomic status (SES) decreased (p = .05), but additive genetic and unique environmental variances were constant across different levels of SES.

Attentional Control Explains Covariation Between Symptoms of Attention-Deficit/Hyperactivity Disorder and Anxiety During Adolescence

Symptoms of attention-deficit/hyperactivity disorder (ADHD) and anxiety are common during adolescence and frequently co-occur. However, the genetic and environmental influences that underlie this co-occurrence are understudied. Using a large twin sample (N = 1,017), we examined cross-sectional genetic and environmental influences on ADHD and anxiety symptoms during childhood. We also explored whether these influences were shared with attentional control, a putative mechanism for symptom comorbidity. We found evidence for common genetic and nonshared environmental influences on the covariation among attentional control, ADHD, and anxiety symptoms, supporting the putative role of attentional control as a mechanism by which comorbid problems may develop. Genetic factors also accounted for symptom co-occurrence after controlling for covariation with attentional control, suggesting the presence of additional unmeasured mechanisms.

Changes of Dynamic Functional Connectivity Associated With Maturity in Late Preterm Infants

Objective: To investigate the changes of dynamic functional connectivity (DFC) in late preterm infants, and assess whether these changes are associated with the indicators measuring the maturity of neonates. Methods: Resting-state fMRI (rs-fMRI) data of eligible neonates was acquired with a 3.0-T MRI scanner in the Department of Radiology, Daping Hospital, Army Medical University (Chongqing, China). After the selection of functional connectivity networks obtained by independent component analysis (ICA), a sliding-window approach was used to cluster all the windows into different states. Then the differences of temporal properties of DFC between groups were compared, and the association between these temporal properties and the degree of maturity was also explored in each state. Results: Eventually, 34 late preterm and 37 term neonates were included in the final analysis. Based on their data, 5 components were located in 5 networks: default-mode (DMN), dorsal attention (DAN), auditory (AUD), sensorimotor (SMN), and visual (VN). Then four reoccurring state patterns of functional connectivity were identified with the k-means clustering method. The late preterm group dwelled significantly longer in State III (late preterm: 33.57 ± 37.64 s, term: 18.50 ± 11.71 s; P = 0.03), which was characterized by general weaker connectivity between networks. Also, the correlation analysis shows the degree of maturity is negatively correlated to the dwell time and fractional windows in State III. Conclusion: Our findings suggested that compared with term infants, late preterm infants preferred to stay in a state with general weak connectivity between networks, but this preference declined as maturity increased.

Didelphis albiventris: an overview of unprecedented transcriptome sequencing of the white-eared opossum

BACKGROUND

The white-eared opossum (Didelphis albiventris) is widely distributed throughout Brazil and South America. It has been used as an animal model for studying different scientific questions ranging from the restoration of degraded green areas to medical aspects of Chagas disease, leishmaniasis and resistance against snake venom. As a marsupial, D. albiventris can also contribute to the understanding of the molecular mechanisms that govern the different stages of organogenesis. Opossum joeys are born after only 13 days, and the final stages of organogenesis occur when the neonates are inside the pouch, depending on lactation. As neither the genome of this opossum species nor its transcriptome has been completely sequenced, the use of D. albiventris as an animal model is limited. In this work, we sequenced the D. albiventris transcriptome by RNA-seq to obtain the first catalogue of differentially expressed (DE) genes and gene ontology (GO) annotations during the neonatal stages of marsupial development.

RESULTS

The D. albiventris transcriptome was obtained from whole neonates harvested at birth (P0), at 5 days of age (P5) and at 10 days of age (P10). The de novo assembly of these transcripts generated 85,338 transcripts. Approximately 30% of these transcripts could be mapped against the amino acid sequences of M. domestica, the evolutionarily closest relative of D. albiventris to be sequenced thus far. Among the expressed transcripts, 2077 were found to be DE between P0 and P5, 13,780 between P0 and P10, and 1453 between P5 and P10. The enriched GO terms were mainly related to the immune system, blood tissue development and differentiation, vision, hearing, digestion, the CNS and limb development.

CONCLUSIONS

The elucidation of opossum transcriptomes provides an out-group for better understanding the distinct characteristics associated with the evolution of mammalian species. This study provides the first transcriptome sequences and catalogue of genes for a marsupial species at different neonatal stages, allowing the study of the mechanisms involved in organogenesis.

The Influence of Taste Liking on the Consumption of Nutrient Rich and Nutrient Poor Foods

Repeated consumption of high-energy nutrient poor foods can lead to undesirable health outcomes such as obesity. Taste plays an important role in food choice, and a better understanding of the links between the taste of foods, individual taste preferences, food choices, and intakes will aid in our understanding of why some people might select and consume unhealthy foods. The present review focuses on three main questions: (1) do nutrient poor and nutrient rich foods significantly differ in taste profile? (2) are humans predisposed toward developing a liking or preference for certain taste profiles? (3) how are individual variations in liking of the basic taste qualities related to long term food intake and adverse health outcomes such as obesity? Results indicated that nutrient poor foods were likely to be sweet, salty and fatty mouthfeel, while the taste profiles of nutrient rich foods were diverse. Although humans are born with a universal liking for sweet and aversion for bitter taste, large individual differences exist in liking of all the basic taste qualities. These individual differences partly explain differences in short term intakes of foods varying in taste profiles. However they fail to sufficiently explain long term food choices and negative health outcomes such as obesity. Future studies should focus on how the full sensory profile of food which includes taste, smell and texture interacts with individual characteristics (e.g., taste or health motivations, taste preferences) to affect consumption of nutrient rich and nutrient poor foods.

RNA sequencing of identical twins discordant for autism reveals blood-based signatures implicating immune and transcriptional dysregulation

Background

A gap exists in our mechanistic understanding of how genetic and environmental risk factors converge at the molecular level to result in the emergence of autism symptoms. We compared blood-based gene expression signatures in identical twins concordant and discordant for autism spectrum condition (ASC) to differentiate genetic and environmentally driven transcription differences, and establish convergent evidence for biological mechanisms involved in ASC.

Methods

Genome-wide gene expression data were generated using RNA-seq on whole blood samples taken from 16 pairs of monozygotic (MZ) twins and seven twin pair members (39 individuals in total), who had been assessed for ASC and autism traits at age 12. Differential expression (DE) analyses were performed between (a) affected and unaffected subjects (N = 36) and (b) within discordant ASC MZ twin pairs (total N = 11) to identify environmental-driven DE. Gene set enrichment and pathway testing was performed on DE gene lists. Finally, an integrative analysis using DNA methylation data aimed to identify genes with consistent evidence for altered regulation in cis.

Results

In the discordant twin analysis, three genes showed evidence for DE at FDR < 10%: IGHG4, EVI2A and SNORD15B. In the case-control analysis, four DE genes were identified at FDR < 10% including IGHG4, PRR13P5, DEPDC1B, and ZNF501. We find enrichment for DE of genes curated in the SFARI human gene database. Pathways showing evidence of enrichment included those related to immune cell signalling and immune response, transcriptional control and cell cycle/proliferation. Integrative methylomic and transcriptomic analysis identified a number of genes showing suggestive evidence for cis dysregulation.

Limitations

Identical twins stably discordant for ASC are rare, and as such the sample size was limited and constrained to the use of peripheral blood tissue for transcriptomic and methylomic profiling. Given these primary limitations, we focused on transcript-level analysis.

Conclusions

Using a cohort of ASC discordant and concordant MZ twins, we add to the growing body of transcriptomic-based evidence for an immune-based component in the molecular aetiology of ASC. Whilst the sample size was limited, the study demonstrates the utility of the discordant MZ twin design combined with multi-omics integration for maximising the potential to identify disease-associated molecular signals.

Optimizing brain performance: Identifying mechanisms of adaptive neurobiological plasticity

Although neuroscience research has debunked the late 19^th century claims suggesting that large portions of the brain are typically unused, recent evidence indicates that an enhanced understanding of neural plasticity may lead to greater insights related to the functional capacity of brains. Continuous and real-time neural modifications in concert with dynamic environmental contexts provide opportunities for targeted interventions for maintaining healthy brain functions throughout the lifespan. Neural design, however, is far from simplistic, requiring close consideration of context-specific and other relevant variables from both species and individual perspectives to determine the functional gains from increased and decreased markers of neuroplasticity. Caution must be taken in the interpretation of any measurable change in neurobiological responses or behavioral outcomes, as definitions of optimal functions are extremely complex. Even so, current behavioral neuroscience approaches offer unique opportunities to evaluate adaptive functions of various neural responses in an attempt to enhance the functional capacity of neural systems.

Genetic and environmental influences on the stability of psychotic experiences and negative symptoms in adolescence

BACKGROUND

Psychotic experiences (PEs) such as paranoia and hallucinations, and negative symptoms (NS) such as anhedonia and flat affect are common in adolescence. Psychotic experiences and negative symptoms (PENS) increase risk for later psychiatric outcomes, particularly when they persist. The extent to which genetic and environmental influences contribute to the stability of PENS in mid-to-late adolescence is unknown.

METHODS

Using the Specific Psychotic Experiences Questionnaire (SPEQ) twice across ~9 months in adolescence, N = 1,448 twin pairs [M = 16.32 (0.68)] reported experiences of paranoia, hallucinations, cognitive disorganization, grandiosity and anhedonia, and their parents reported on a range of NS. Individuals were split into low-scoring, decreasing, increasing and persistent groups for each subscale. Frequencies and mean differences in distress, depression traits and emotional problems were investigated across groups. Longitudinal structural equation modelling was used to estimate the aetiological components underlying the stability of PENS.

RESULTS

Phenotypic stability was moderate for all PENS (r = .59-.69). Persistent PENS across 9 months were associated with greater levels of distress (V = 0.15-0.46, for PEs only), depression traits (d = 0.47-1.67, except grandiosity) and emotional problems (d = 0.47-1.47, except grandiosity and anhedonia) at baseline compared to groups with transitory or low levels of PENS. At both ages PENS were heritable and influenced by shared and nonshared environment. Genetic influences contributed 38%-62% and shared environment contributed 13%-33% to the stability of PENS. Nonshared environment contributed 34%-41% (12% for parent-rated NS). There was strong overlap of genetic and shared environmental influences across time, and lower overlap for nonshared environment. Imperfect stability of PENS was at least partly due to nonshared environmental influences.

CONCLUSIONS

When adolescent PENS persist over time, they are often characterized by more distress, and higher levels of other psychopathology. Both genetic and environmental effects influence stability of PENS.

Mother-infant interactions with firstborns and secondborns: A within-family study of European Americans

Given the large numbers of families with more than one child, understanding similarities and differences in siblings' behaviors and in parents' interactions with their sibling infants is an important goal for advancing more representative developmental science. This study employed a within-family design to examine mean-level consistency and individual-order agreement in 5-month-old sibling behaviors and maternal parenting practices with their firstborns and secondborns (ns = 61 mothers and 122 infants). Each infant was seen independently with mother. Firstborn infants were more social with their mothers and engaged in more exploration with objects than secondborn infants; firstborn and secondborn infants' behaviors were correlated for smiling, distress communication, and efficiency of exploration. Mothers engaged in more physical encouragement, social exchange, didactic interaction, material provisioning, and language with their firstborns than with their secondborns. Notably, only maternal nurturing (e.g., feeding, holding) did not differ in mean level when mothers were with their two infants. However, mean differences in mothers' social exchange and material provisioning with their two children attenuated to nonsignificance when controlling for differences in siblings' behaviors. Individual-order agreement of mothers' behaviors with firstborn and secondborn infants (across an average of almost 3 years) was only moderate. These findings suggest that mother-firstborn interactions may differ from mother-secondborn interactions. Future research should move beyond studying mother-firstborn dyads to understand broader family and developmental processes.

Physical and Cultural Inheritance Enhance Agency, but What are the Origins of this Concern to Establish a Legacy? A Nationally-Representative Twin Study of Erikson's Concept of Generativity

Generativity—showing concern to establish and guide future generations—has been argued to be a biological adaptation central to cumulative culture and survival, but also, in turn, to be a cultural adaptation dependent on norms. From the perspective of human agency, concern for the future has played a key role in raising agency for generations that follow by creating infrastructure and cultural inheritance. Here, in a population-representative sample of 756 twin-pairs, we present the first test of the genetic and environmental structure of generativity using the Loyola Generativity Scale (short). Genetic analysis of scale sum-scores revealed that shared environmental effects were comparable in magnitude or exceeded effects estimated for genetic differences (A = 0.30 CI95 [− 0.01, 0.61], C = 0.41 [0.25, 0.56], E = 0.86 [0.79, 0.93]). At the item level, a well-fitting genetically-informed model suggested 3 factors influencing generativity via a common-pathway structure. The first was tentatively characterized as reflecting a heritable general concern for the future. The second reflected being a valued source of advice and assistance. The third factor showed only unique environment effects and had as its strongest indicator having had a good influence on the lives of others. Replicability of this structure should be tested in the full version of the scale. Work is needed also to validate influences of generativity on vocations such as teaching and on philanthropic activity improving life for subsequent generations.

Longitudinal Course and Correlates of Parents' Differential Treatment of Siblings in Mexican-Origin Families

Parents' differential treatment (PDT) is a common family dynamic that has been linked to youth development and well-being, including adjustment problems and poor sibling relationships. Much less is known, however, about the developmental course of PDT and the conditions under which parents treat their children differently in adolescence and young adulthood. This study examined longitudinal changes in mothers' and fathers' differential warmth and conflict with their two offspring from early adolescence through young adulthood and examined parents' experiences of individual stress (depressive symptoms and role overload) and marital difficulties as time-varying correlates of (changes in) PDT. We also tested crossover effects to determine whether mothers' experiences of individual stress and marital difficulties were linked to fathers' differential treatment, and vice versa. Participants were mothers, fathers, and two siblings from 246 Mexican-origin families who were interviewed in their homes on three occasions over 8 years. Multilevel models revealed that mothers' and fathers' differential conflict with their two children increased until middle adolescence and then declined into young adulthood, but there were no changes over time for parents' differential warmth. In general, both mothers' and fathers' levels of differential treatment were exacerbated by their own experiences of individual stress and marital difficulties and also by the experiences of their spouses. However, in some cases, greater stress than usual was linked to less differential treatment than usual.

Early life experiences: Meaningful differences within and between families

Previous research has focused on differences in early life experiences that occur between families and their impact on children's development. However, less is known about the variations in early life experiences that occur within families. Here, 53 British mothers (mean age = 34.46 years; SD = 4.35) of newborn infants (mean age = 1.68 months, SD = 0.96) used a smartphone application (app) to repeatedly rate their wellbeing and support and to report their baby's and their own dietary and sleeping patterns (4 app alerts per week for 3 weeks; 12 assessments in total). We found that the app was a practicable tool for observing early life experiences, and that early life experiences differed on average to a greater extent within, rather than between families (59% versus 41% of the total variance). We also found preliminary evidence for meaningful associations among contemporaneous within-family variations in early life experiences.

Nurturing Our Better Nature: A Proposal for Cognitive Integrity as a Foundation for Autonomous Living

As we account for the genetic and environmental influences on morally-relevant character traits like intellectual honesty, industriousness, and self-control, do we risk becoming ever less accountable to ourselves? Behavioral genetic research suggests that about half the variance in such character traits is likely attributable to heredity, and a small fraction to the shared family environment. The remaining 40-60% is explained by neither genes nor family upbringing. This raises the question: how active a role can individuals play in shaping their own character? What, if anything, can and should one do to take responsibility for the kind of person one becomes? This paper sketches a novel theoretical proposal for addressing these questions, by drawing on several previously disparate lines of research within behavior genetics, philosophy, and experimental psychology. Our core proposal concerns the metacognitive capacity to engage in active, reality-based cognition, as opposed to passive, stimulus-driven processing or an active pretense at cognition (i.e., self-deception). We review arguments and evidence indicating that human beings both can and should exercise this capacity, which we have termed "cognitive integrity." We argue that doing so can in a certain sense "set us free" of our genetic and environmental influences-not by rendering them irrelevant, but by giving us the awareness and motivation to manage them more responsibly. This perspective has important implications for guiding the development of psychosocial interventions, and for informing how we direct ourselves more generally, both as individuals and as a society.

Monozygotic twin differences in school performance are stable and systematic

School performance is one of the most stable and heritable psychological characteristics. Notwithstanding, monozygotic twins (MZ), who have identical genotypes, differ in school performance. These MZ differences result from non-shared environments that do not contribute to the similarity within twin pairs. Because to date few non-shared environmental factors have been reliably associated with MZ differences in school performance, they are thought to be idiosyncratic and due to chance, suggesting that the effect of non-shared environments on MZ differences are age- and trait-specific. In a sample of 2768 MZ twin pairs, we found first that MZ differences in school performance were moderately stable from age 12 through 16, with differences at the ages 12 and 14 accounting for 20% of the variance in MZ differences at age 16. Second, MZ differences in school performance correlated positively with MZ differences across 16 learning-related variables, including measures of intelligence, personality and school attitudes, with the twin who scored higher on one also scoring higher on the other measures. Finally, MZ differences in the 16 learning-related variables accounted for 22% of the variance in MZ differences in school performance at age 16. These findings suggest that, unlike for other psychological domains, non-shared environmental factors affect school performance in systematic ways that have long-term and generalist influence. Our findings should motivate the search for non-shared environmental factors responsible for the stable and systematic effects on children's differences in school performance. A video abstract of this article can be viewed at: https://youtu.be/0bw2Fl_HGq0.