The Beijing Twin Study (BeTwiSt): a longitudinal study of child and adolescent development

Familial genetic and environmental transmission of depression: A multi-informant twin family study

The phenomenon of familial clustering in depression is well established, yet the mechanisms by which depression is transmitted within families remain poorly understood. In the current study, we investigate the familial genetic and environmental transmission of depression by incorporating data from both adolescent twins and their parents. A total of 987 twin families were recruited from the Beijing Twin Study. Depression assessments were conducted for both adolescents and their parents. Twins' depression was assessed through reports from both the twins themselves and their parents, while parental depression was assessed by parental self-report. We employed a nuclear twin family model to examine genetic and environmental influences on adolescent depression. Our results, based on both self- and parent-report, demonstrate significant additive and dominant genetic influences on depression. We also found mild yet significant sibling environmental influences, while familial environmental influences were absent. Notably, parent-reported depression showed higher heritability but lower unique environmental influences compared with self-reported depression. These results highlight the important role of genetic transmission and sibling environmental transmission in explaining depression. Our study delineates the underlying mechanism of familial transmission in depression and can inform early treatments to halt transmission during adolescence.

Heritability of cerebral blood flow in adolescent and young adult twins: an arterial spin labeling perfusion imaging study

Blood perfusion is a fundamental physiological property of all organs and is closely linked to brain metabolism. Genetic factors were reported to have important influences on cerebral blood flow. However, the profile of genetic contributions to cerebral blood flow in adolescents or young adults was underexplored. In this study, we recruited a sample of 65 pairs of same-sex adolescent or young adult twins undergoing resting arterial spin labeling imaging to conduct heritability analyses. Our findings indicate that genetic factors modestly affect cerebral blood flow in adolescents or young adults in the territories of left anterior cerebral artery and right posterior cerebral artery, with the primary contribution being to the frontal regions, cingulate gyrus, and striatum, suggesting a profile of genetic contributions to specific brain regions. Notably, the regions in the left hemisphere demonstrate the highest heritability in most regions examined. These results expand our knowledge of the genetic basis of cerebral blood flow in the developing brain and emphasize the importance of regional analysis in understanding the heritability of cerebral blood flow. Such insights may contribute to our understanding of the underlying genetic mechanism of brain functions and altered cerebral blood flow observed in youths with brain disorders.

Heritability of Justice Sensitivity

Abstract. Justice is one of the fundamental principles in human evolution, and justice sensitivity from the pro-self (e.g., as a victim) and the prosocial perspective (e.g., as an observer, beneficiary, and perpetrator) matters in mental wellness and social interaction. However, the extent to which individual difference in justice sensitivity is influenced by genetic versus environmental factors remains unclear. Using a sample with 244 twin pairs, the present research attempts to determine the extent to which genetic factors play a role in the inter-individual difference of justice sensitivity as well as whether different facets of justice sensitivity, namely, pro-self and prosocial perspectives, share a common genetic basis. Results showed that (1) all facets of justice sensitivity were moderately heritable (21–33%) and that the non-shared environmental factors plus measurement error accounted for the rest of the variations (67–79%); (2) associations between the prosocial facets of justice sensitivity were driven by common genetic ( rg = .50–.65) and non-shared environmental (plus measurement error; re = .24–.65) influences, whereas no significant genetic link was found between the pro-self and prosocial facets. The current findings provide novel evidence that sensitivity to injustice, especially to others’ suffering, is fundamentally grounded upon genetic origin, thereby shedding light on the nature and nurture aspects of justice behavior.

Negative Parenting Affects Adolescent Internalizing Symptoms Through Alterations in Amygdala-Prefrontal Circuitry: A Longitudinal Twin Study

BACKGROUND

The synergic interaction of risk genes and environmental factors has been thought to play a critical role in mediating emotion-related brain circuitry function and dysfunction in depression and anxiety disorders. Little, however, is known regarding neurodevelopmental bases underlying how maternal negative parenting affects emotion-related brain circuitry linking to adolescent internalizing symptoms and whether this neurobehavioral association is heritable during adolescence.

METHODS

The effects of maternal parenting on amygdala-based emotional circuitry and internalizing symptoms were examined by using longitudinal functional magnetic resonance imaging among 100 monozygotic twins and 78 dizygotic twins from early adolescence (age 13 years) to mid-adolescence (age 16 years). The mediation effects among variables of interest and their heritability were assessed by structural equation modeling and quantitative genetic analysis, respectively.

RESULTS

Exposure to maternal negative parenting was positively predictive of stronger functional connectivity of the amygdala with the ventrolateral prefrontal cortex. This neural pathway mediated the association between negative parenting and adolescent depressive symptoms and exhibited moderate heritability (21%).

CONCLUSIONS

These findings highlight that maternal negative parenting in early adolescence is associated with the development of atypical amygdala-prefrontal connectivity in relation to internalizing depressive symptoms in mid-adolescence. Such abnormality of emotion-related brain circuitry is heritable to a moderate degree.

Dopaminergic and neurotrophic genetic polymorphisms modulate the implicit gender-science stereotype

Genetic approaches to both the gender-science stereotype and implicit social cognition have received increasing attention in recent years. We explored whether single nucleotide polymorphisms (SNPs) in dopaminergic and neurotrophic systems (i.e., COMT, BDNF genotypes) explain variations in the implicit gender-science stereotype. We genotyped 413 adolescents and assessed their implicit gender-science stereotype with the Implicit Association Test. Replication on a subsample (N = 312) was conducted 2 years later. Results showed that SNP-level variations within the COMT and BDNF genes were consistently associated with the implicit gender-science stereotype in both investigations. These findings suggest that variants in the COMT and BDNF genes may contribute to the variation of implicit gender-science stereotype.

Rumination thinking in childhood and adolescence: a brief review of candidate genes

BACKGROUND

rumination has been reported as a cognitive vulnerability factor in adolescent and adult depression. The present brief review aimed at summarizing the results of the genetic studies that investigate the candidate genes for rumination in children and adolescents.

METHODS

bibliographic research was conducted on PubMed and Science Direct from their inception to February 2020. The search terms used were: 'rumination, ruminative thinking, repetitive thinking and 'gene, gen*'.

RESULTS

eight studies were identified. Results suggest that variations in the 5-HTTLPR and BDNF genes may contribute to the tendency to ruminate, modelling the relationship between life stress and rumination.

LIMITATIONS

the interpretation of these results is limited by the sample sizes of the selected studies, the study designs, and the heterogeneity of the instruments assessing rumination.

CONCLUSIONS

these findings partially support the notion that variation in in the 5-HTTLPR and BDNF genes is associated with biological sensitivity to rumination.

Heritability of reflexive social attention triggered by eye gaze and walking direction: common and unique genetic underpinnings

BACKGROUND

Social attention ability is crucial for human adaptive social behaviors and interpersonal communications, and the malfunction of which has been implicated in autism spectrum disorder (ASD), a highly genetic neurodevelopmental disorder marked by striking social deficits.

METHODS

Using a classical twin design, the current study investigated the genetic contribution to individual variation in social and non-social attention abilities, and further probed their potential genetic linkage. Moreover, individual autistic traits were further measured in an independent group of non-twin participants to examine the hypothetical link between the core social attention ability and ASD.

RESULTS

We found reliable genetic influences on the social attentional effects induced by two distinct cues (eye gaze and walking direction), with 91% of their covariance accounted for by common genetic effects. However, no evidence of heritability or shared genetic effects was observed for the attentional effect directed by a non-social cue (i.e. arrow direction) and its correlation with the social attention ability. Remarkably, one's autistic traits could well predict his/her heritable core social attention ability extracted from the conventional social attentional effect.

CONCLUSIONS

These findings together suggest that human social attention ability is supported by unique genetic mechanisms that can be shared across different social, but not non-social, processing. Moreover, they also encourage the identification of 'social attention genes' and highlight the critical role of the core human social attention ability in seeking the endophenotypes of social cognitive disorders including ASD.

A Laboratory Study of the McGurk Effect in 324 Monozygotic and Dizygotic Twins

Multisensory integration of information from the talker's voice and the talker's mouth facilitates human speech perception. A popular assay of audiovisual integration is the McGurk effect, an illusion in which incongruent visual speech information categorically changes the percept of auditory speech. There is substantial interindividual variability in susceptibility to the McGurk effect. To better understand possible sources of this variability, we examined the McGurk effect in 324 native Mandarin speakers, consisting of 73 monozygotic (MZ) and 89 dizygotic (DZ) twin pairs. When tested with 9 different McGurk stimuli, some participants never perceived the illusion and others always perceived it. Within participants, perception was similar across time (r = 0.55 at a 2-year retest in 150 participants) suggesting that McGurk susceptibility reflects a stable trait rather than short-term perceptual fluctuations. To examine the effects of shared genetics and prenatal environment, we compared McGurk susceptibility between MZ and DZ twins. Both twin types had significantly greater correlation than unrelated pairs (r = 0.28 for MZ twins and r = 0.21 for DZ twins) suggesting that the genes and environmental factors shared by twins contribute to individual differences in multisensory speech perception. Conversely, the existence of substantial differences within twin pairs (even MZ co-twins) and the overall low percentage of explained variance (5.5%) argues against a deterministic view of individual differences in multisensory integration.

On the Etiology of Self-Enhancement and Its Association With Psychological Well-Being

Self-enhancement, the motive to view oneself in positive light, and its manifestations have received wide attention in behavioral sciences. The self-enhancement manifestations vary on a continuum from a subjective level (agentic narcissism, communal narcissism, narcissistic grandiosity) through an intermediate level (better-than-average judgments) to an objective level (overclaiming one’s knowledge). Prior research has established the heritability of self-enhancement manifestations at the subjective and intermediate levels. The present twin study demonstrated that (1) the objective level of self-enhancement manifestation is also heritable; (2) a common core, which is moderately heritable, underlies the three levels of self-enhancement manifestations; (3) the relation between self-enhancement (manifested at all three levels) and psychological well-being is partly heritable; and (4) environmental influences, either shared by or unique to family members, are evident through (1), (2), and (3). The findings deepen understanding of the etiology of individual differences in self-enhancement and their links to psychological well-being.

The Beijing Twin Study (BeTwiSt): An Update

The Beijing Twin Study (BeTwiSt), which was established in 2006, is an ongoing study aiming to investigate the genetic and environmental etiology of adolescent psychopathology. Resting-state brain imaging datasets have been examined for same-sex twins, and other psychological traits and emotional and behavioral variables have been examined for all twins. Based on the registry, the main findings regarding the etiological mechanism underlying adolescent development, magnetic resonance imaging results, and genetic and environmental influences on other psychological traits have been published. This article summarizes the key findings in these three areas and discusses future plans for the BeTwiSt.

Genetic contribution to the phenotypic correlation between trait impulsivity and resting-state functional connectivity of the amygdala and its subregions

Trait impulsivity, a predisposition to respond to stimuli without regard for the potentially negative consequences, contributes to many maladaptive behaviors. Studies have shown that both genetic factors and interregional functional interactions underlie trait impulsivity. However, whether common genes contribute to both trait impulsivity and its neural basis is still unknown. This study investigated the phenotypic correlations between trait impulsivity and the resting-state functional connectivity (rsFC) of the amygdala as well as its subregions and the genetic contribution to the phenotypic correlations. By recruiting a sample of 292 twins in late adolescence and young adulthood, we found that trait impulsivity was positively correlated with the rsFC between the left full amygdala and the right dorsolateral prefrontal cortex (DLPFC). Further analyses on the subregions of the amygdala showed that trait impulsivity was positively correlated with the rsFCs between the left basolateral (BL) amygdala and both the right DLPFC and the right inferior frontal gyrus and with the rsFCs between the right superficial (SF) amygdala and both the dorsal anterior cingulate cortex and right anterior insula. Bivariate genetic modelling analyses found genetic overlaps between trait impulsivity and the rsFC of the left full amygdala or the left BL amygdala with the right DLPFC. The proportions of phenotypic associations accounted for by overlapping genes were 82% and 60%, respectively. These results provide evidence for the genetic overlap between trait impulsivity and the intrinsic brain functional connectivity centered at the amygdala and especially at its BL subregion.

Do Narcissists Enjoy Visiting Social Networking Sites? It Depends on How Adaptive They Are

Previous evidence suggests that narcissistic people tend to visit social networking sites (SNS) frequently, but the emotions accompanying their engagement on such sites has not been a significant subject of study. Therefore, we examined the relationship between narcissism and the affective experience on SNS in two different samples. To do so, we not only examined narcissism as a whole but also distinguished between adaptive and maladaptive narcissism. Results of the two studies consistently showed that: (1) narcissism as a whole was not correlated with the SNS affective experience; (2) maladaptive narcissism was predictive of a worse affective experience on SNS; and (3) partly due to a positive correlation with self-esteem, adaptive narcissism was associated with a better SNS affective experience. In addition, these findings held with SNS activities considered in simultaneity. The present research extends our understanding of the relationship between narcissism and social networking as well as that between emotion and social networking.

Suspiciousness in young minds: Convergent evidence from non-clinical, clinical and community twin samples

BACKGROUND

We validated the Social Mistrust Scale (SMS) and utilized it to examine the structure, prevalence, and heritability of social mistrust in a large sample of Chinese children and adolescents.

METHODS

In Study 1, a large sample of healthy twins (N=2094) aged 8 to 14years (M=10.27years, SD=2) completed the SMS. Structural equation modeling (SEM) was conducted to assess the structure of the SMS and to estimate the heritability of social mistrust in a sub-sample of twins (n=756 pairs). In Study 2, 32 adolescents with childhood-onset schizophrenia were compared with 34 healthy controls on levels of suspiciousness and clinical symptoms to examine the associations between the SMS and the Positive and Negative Syndrome Scale (PANSS).

RESULTS

We found a three-factor structure for social mistrust (home, school, and general mistrust). Social mistrust was found to be moderately - heritable (19%-40%), with mistrust at home most strongly influenced by genetic factors. Compared with 11.76% of the healthy controls, 56.25% of the adolescents with early-onset schizophrenia exhibited very high levels of social mistrust on all three subscales of the SMS. The SMS exhibited good discriminant validity in distinguishing adolescents with childhood-onset schizophrenia from healthy controls and showed associations with a broad range of symptoms assessed by the PANSS.

CONCLUSIONS

Social mistrust assessed by the SMS may be heritable. The SMS demonstrates good discriminant validity with clinical diagnoses of schizophrenia. However, it seems to be correlated with multiple aspects of psychopathology in the schizophrenia group, rather than being specific to delusional ideation/paranoia.

Genetic Contribution to Variation in Risk Taking: A Functional MRI Twin Study of the Balloon Analogue Risk Task

Excessive risk-taking behaviors have been implicated as a potential endophenotype for substance use disorders and psychopathological gambling. However, the genetic and environmental influences on risk taking and the risk-related brain activations remain unclear. This study investigated the heritability of risk taking and the genetic influence on individual variation in risk-related brain activation. The Balloon Analogue Risk Task was used to assess individuals’ risk-taking behavior. In a sample of 244 pairs of young adult twins, we found that there was a moderate heritability (41%) of risk taking. Using voxel-level analysis, we found a moderate genetic influence on risk-related brain activation. We also found a moderate genetic correlation between risk-taking behavior and risk-related brain activation in the left insula, right striatum, and right superior parietal lobule in the active-choice condition. The present study provides important evidence for the genetic correlation between risk-taking behavior and risk-related brain activation.

The Hierarchical Organization of the Default, Dorsal Attention and Salience Networks in Adolescents and Young Adults

An important characteristic of spontaneous brain activity is the anticorrelation between the core default network (cDN) and the dorsal attention network (DAN) and the salience network (SN). This anticorrelation may constitute a key aspect of functional anatomy and is implicated in several brain disorders. We used dynamic causal modeling to assess the hypothesis that a causal hierarchy underlies this anticorrelation structure, using resting-state fMRI of healthy adolescent and young adults (N = 404). Our analysis revealed an asymmetric effective connectivity, such that the regions in the SN and DAN exerted an inhibitory influence on the cDN regions; whereas the cDN exerted an excitatory influence on the SN and DAN regions. The relative strength of efferent versus afferent connections places the SN at the apex of the hierarchy, suggesting that the SN modulates anticorrelated networks with descending hierarchical connections. In short, this study of directed neuronal coupling reveals a causal hierarchical architecture that generates or orchestrates anticorrelation of brain activity. These new findings shed light on functional integration of intrinsic brain networks at rest and speak to future dynamic causal modeling studies of large-scale networks.

Heritable aspects of biological motion perception and its covariation with autistic traits

The ability to detect biological motion (BM) and decipher the meaning therein is essential to human survival and social interaction. However, at the individual level, we are not equally equipped with this ability. In particular, impaired BM perception and abnormal neural responses to BM have been observed in autism spectrum disorder (ASD), a highly heritable neurodevelopmental disorder characterized by devastating social deficits. Here, we examined the underlying sources of individual differences in two abilities fundamental to BM perception (i.e., the abilities to process local kinematic and global configurational information of BM) and explored whether BM perception shares a common genetic origin with autistic traits. Using the classical twin method, we found reliable genetic influences on BM perception and revealed a clear dissociation between its two components-whereas genes account for about 50% of the individual variation in local BM processing, global BM processing is largely shaped by environment. Critically, participants' sensitivity to local BM cues was negatively correlated with their autistic traits through the dimension of social communication, with the covariation largely mediated by shared genetic effects. These findings demonstrate that the ability to process BM, especially with regard to its inherent kinetics, is heritable. They also advance our understanding of the sources of the linkage between autistic symptoms and BM perception deficits, opening up the possibility of treating the ability to process local BM information as a distinct hallmark of social cognition.

The Association of Cigarette Smoking With Depression and Anxiety: A Systematic Review

BACKGROUND

Many studies report a positive association between smoking and mental illness. However, the literature remains mixed regarding the direction of this association. We therefore conducted a systematic review evaluating the association of smoking and depression and/or anxiety in longitudinal studies.

METHODS

Studies were identified by searching PubMed, Scopus, and Web of Science and were included if they: (1) used human participants, (2) were longitudinal, (3) reported primary data, (4) had smoking as an exposure and depression and/or anxiety as an outcome, or (5) had depression and/or anxiety as the exposure and smoking as an outcome.

RESULTS

Outcomes from 148 studies were categorized into: smoking onset, smoking status, smoking heaviness, tobacco dependence, and smoking trajectory. The results for each category varied substantially, with evidence for positive associations in both directions (smoking to later mental health and mental health to later smoking) as well as null findings. Overall, nearly half the studies reported that baseline depression/anxiety was associated with some type of later smoking behavior, while over a third found evidence that a smoking exposure was associated with later depression/anxiety. However, there were few studies directly supporting a bidirectional model of smoking and anxiety, and very few studies reporting null results.

CONCLUSIONS

The literature on the prospective association between smoking and depression and anxiety is inconsistent in terms of the direction of association most strongly supported. This suggests the need for future studies that employ different methodologies, such as Mendelian randomization (MR), which will allow us to draw stronger causal inferences.

IMPLICATIONS

We systematically reviewed longitudinal studies on the association of different aspects of smoking behavior with depression and anxiety. The results varied considerably, with evidence for smoking both associated with subsequent depression and anxiety, and vice versa. Few studies supported a bidirectional relationship, or reported null results, and no clear patterns by gender, ethnicity, clinical status, length to follow-up, or diagnostic test. Suggesting that despite advantages of longitudinal studies, they cannot alone provide strong evidence of causality. Therefore, future studies investigating this association should employ different methods allowing for stronger causal inferences to be made, such as MR.

Nostalgia and Self-Enhancement

We addressed phenotypic and genetic research questions regarding nostalgia and self-enhancement. At the phenotypic level (178 university students; Study 1), we found that nostalgia was moderately associated with self-enhancement. At the genotypic level (232 twin pairs; Study 2), we found that nostalgia, self-enhancement, and their relation were largely heritable. Our findings shed light on two heavily investigated traits and open up exciting research directions.

Investigating Unique Environmental Influences of Parenting Practices on Youth Anxiety

The associations between parenting practices and adolescent anxiety symptoms were examined in both individual and monozygotic (MZ) twin differences levels. Participants were 804 pairs of Chinese MZ adolescent twins aged 10–18 years ( M = 13.57, SD = 2.67, 52% females). Twins’ anxiety symptoms were assessed by self- and parent-reports. Twins also reported their perceived parenting practices. On the individual level, parental warmth-reasoning was negatively, whereas harshness-hostility was positively, associated with both self- and parent-reported youth anxiety. On the MZ-twin differences level, the magnitudes of the associations between parenting practices and youth anxiety were decreased. MZ-twin difference in parental warmth-reasoning remained significantly associated with self- and parent-reported youth anxiety; MZ-twin difference in parental harsh-hostility was only significantly associated with self-reported youth anxiety. This study indicated that parental warmth-reasoning and harshness-hostility may be unique environmental experiences that influence youth anxiety, and illustrated the necessity of controlling for gene-environment correlations when examining the true environmental effects of parenting on child behavior.

Male = Science, Female = Humanities

The gender-science stereotype of associating males, rather than females, with science is pervasive and influential. The present study challenged the common-sense assumption that it is environment that leads to the gender-science stereotype by conducting a genetically informative study. A total of 304 pairs of twins (152 monozygotic [MZ] and 152 dizygotic [DZ]) completed explicit and implicit gender-science stereotype measures twice across 2 years. Results showed that both explicit and implicit gender-science stereotypes were heritable, with significant nonshared environmental influence. Moreover, genetic and nonshared environmental factors influencing the explicit gender-science stereotype also affected the implicit gender-science stereotype to some extent. These findings have important implications for understanding the nature of the gender-science stereotype and implicit social cognition.

The BDNF Val66Met Polymorphism Interacts with Maternal Parenting Influencing Adolescent Depressive Symptoms: Evidence of Differential Susceptibility Model

Although depressive symptoms are common during adolescence, little research has examined gene-environment interaction on youth depression. This study chose the brain-derived neurotrophic factor (BDNF) gene, tested the interaction between a functional polymorphism resulting amino acid substitution of valine (Val) to methionine (Met) in the proBDNF protein at codon 66 (Val66Met), and maternal parenting on youth depressive symptoms in a sample of 780 community adolescents of Chinese Han ethnicity (aged 11-17, M = 13.6, 51.3 % females). Participants reported their depressive symptoms and perceived maternal parenting. Results indicated the BDNF Val66Met polymorphism significantly moderated the influence of maternal warmth-reasoning, but not harshness-hostility, on youth depressive symptoms. Confirmatory model evaluation indicated that the interaction effect involving warmth-reasoning conformed to the differential-susceptibility rather than diathesis-stress model of person-X-environment interaction. Thus, Val carriers experienced less depressive symptoms than Met homozygotes when mothering was more positive but more symptoms when mothering was less positive. The findings provided evidence in support of the differential susceptibility hypothesis of youth depressive symptoms and shed light on the importance of examining the gene-environment interaction from a developmental perspective.

Genetic Effects on Fine-Grained Human Cortical Regionalization

Various brain structural and functional features such as cytoarchitecture, topographic mapping, gyral/sulcal anatomy, and anatomical and functional connectivity have been used in human brain parcellation. However, the fine-grained intrinsic genetic architecture of the cortex remains unknown. In the present study, we parcellated specific regions of the cortex into subregions based on genetic correlations (i.e., shared genetic influences) between the surface area of each pair of cortical locations within the seed region. The genetic correlations were estimated by comparing the correlations of the surface area between monozygotic and dizygotic twins using bivariate twin models. Our genetic subdivisions of diverse brain regions were reproducible across 2 independent datasets and corresponded closely to fine-grained functional specializations. Furthermore, subregional genetic correlation profiles were generally consistent with functional connectivity patterns. Our findings indicate that the magnitude of the genetic covariance in brain anatomy could be used to delineate the boundaries of functional subregions of the brain and may be of value in the next generation human brain atlas.

BDNF Val66Met, stress, and positive mothering: Differential susceptibility model of adolescent trait anxiety

Etiological research has indicated the gene-environment interaction (G × E) on adolescent anxiety. This study aimed to examine how the BDNF Val66Met polymorphism interacted with stressful life events and positive mothering to influence youth trait anxiety. The study sample included 780 community adolescents of Chinese Han ethnicity (M = 13.6, 51.3% females). Participants' trait anxiety, exposure to stressful life events, and mother's warmth-reasoning were assessed by self-reported questionnaires. We found that BDNF Val66Met polymorphism significantly moderated the influences of stressful life events and mother's warmth-reasoning on adolescent anxiety. The influences were significantly greater in adolescents carrying one or two Val allele than those with Met/Met genotype. Moreover, the G × E interactions were more consistent with the differential susceptibility than the diathesis-stress model. Adolescents carrying Val allele who were more susceptible to adversity were also more likely to benefit from supportive experiences. These findings provide novel evidence for the role of BDNF Val66Met as a genetic susceptibility modulating the influences of stressful life events and mother's warmth-reasoning on adolescent anxiety. We speculate that BDNF Val66Met may moderate anxious youths' responses to mindfulness-based stress reduction program and family-based treatment targeting the enhancement of positive parenting.

Narcissism predicts impulsive buying: phenotypic and genetic evidence

Impulsive buying makes billions of dollars for retail businesses every year, particularly in an era of thriving e-commerce. Narcissism, characterized by impulsivity and materialism, may serve as a potential antecedent to impulsive buying. To test this hypothesis, two studies examined the relationship between narcissism and impulsive buying. In Study 1, we surveyed an online sample and found that while adaptive narcissism was not correlated with impulsive buying, maladaptive narcissism was significantly predictive of the impulsive buying tendency. By investigating 304 twin pairs, Study 2 showed that global narcissism and its two components, adaptive and maladaptive narcissism, as well as the impulsive buying tendency were heritable. The study found, moreover, that the connections between global narcissism and impulsive buying, and between maladaptive narcissism and impulsive buying were genetically based. These findings not only establish a link between narcissism and impulsive buying but also help to identify the origins of the link. The present studies deepen our understanding of narcissism, impulsive buying, and their interrelationship.

Investigating genetic and environmental contributions to adolescent externalizing behavior in a collectivistic culture: a multi-informant twin study

BACKGROUND

Little is known about the etiology of adolescents' externalizing behavior (Ext) in collectivistic cultures. We aimed to fill this gap by investigating the genetic and environmental influences on Ext in Chinese adolescents. The etiological heterogeneity of aggression (AGG) and rule breaking (RB) was also examined.

METHOD

The study sample included 908 pairs of same-sex twins aged from 10 to 18 years (mean = 13.53 years, s.d. = 2.26). Adolescents' Ext were assessed with the Achenbach System of Empirically Based Assessment including Child Behavior Checklist, Teacher Report Form, and Youth Self-Report.

RESULTS

Univariate genetic analyses showed that genetic influences on all measures were moderate ranging from 34% to 50%, non-shared environmental effects ranged from 23% to 52%, and shared environmental effects were significant in parent- and teacher-reported measures ranging from 29% to 43%. Bivariate genetic analyses indicated that AGG and RB shared large genetic influences (r g = 0.64-0.79) but moderate non-shared environmental factors (r e = 0.34-0.52).

CONCLUSIONS

Chinese adolescents' Ext was moderately influenced by genetic factors. AGG and RB had moderate independent genetic and non-shared environmental influences, and thus constitute etiologically distinct dimensions within Ext in Chinese adolescents. The heritability of AGG, in particular, was smaller in Chinese adolescents than suggested by previous data obtained on Western peers. This study suggests that the collectivistic cultural values and Confucianism philosophy may attenuate genetic potential in Ext, especially AGG.

Genetic and environmental contributions to anxiety among Chinese children and adolescents--a multi-informant twin study

BACKGROUND

Child and adolescent anxiety has become a major public health concern in China, but little was known about the etiology of anxiety in Chinese children and adolescents. The present study aimed to investigate genetic and environmental influences on trait anxiety among Chinese children and adolescents. Rater, sex, and age differences on these estimates were also examined.

METHODS

Self-reported and parent-reported child's trait anxiety was collected from 1,104 pairs of same-sex twins aged 9-18 years. Genetic models were fitted to data from each informant to determine the genetic (A), shared (C), and non-shared environmental (E) influences on trait anxiety.

RESULTS

The parameter estimates and 95% confidence intervals (CI) of A, C, E on self-reported trait anxiety were 50% [30%, 60%], 5% [0%, 24%], 45% [40%, 49%]. For parent-reported data, the corresponding parameter estimates were 63% [47%, 78%], 13% [1%, 28%], and 24% [22%, 27%], respectively. The heritability of anxiety was higher in girls for self-reported data, but higher in boys for parent-reported data. There was no significant age difference in genetic and environmental contributions for self-reported data, but a significant increase of heritability with age for parent-reported data.

CONCLUSIONS

The trait anxiety in Chinese children and adolescents was highly heritable. Non-shared environmental factors also played an important role. The estimates of genetic and environmental effects differed by rater, sex and age. Our findings largely suggest the cross-cultural generalizability of the etiological model of child and adolescent anxiety.

Etiological heterogeneity of symptom dimensions of adolescent depression

The aim was to investigate the underlying factor structure of adolescent depression and etiological heterogeneity in the symptom dimensions of adolescent depression. The sample included 842 pairs of same-sex adolescent twins, among which 613 pairs were monozygotic twins and 229 pairs were dizygotic twins. The ages of the participants ranged from 11 to 17 years (M = 13.64, SD = 1.80). Adolescents' depressive symptoms were assessed using the self-reported Children's Depression Inventory. Exploratory and confirmatory factor analyses were used to explore the factor structure of youth depression and twin genetic analyses were employed to estimate genetic and environmental influences on the derived dimensions. Results showed that adolescent depression encompassed five correlated dimensions: dysphoria mood, somatic symptoms, study and externalizing problems, anhedonia symptoms, and cognitive symptoms. These five symptom dimensions had heterogeneous etiologies: Dysphoria mood, somatic symptoms, and cognitive symptoms were moderately heritable (heritability ranged from 33 to 40%), whereas study and externalizing problems, and anhedonia symptoms were mainly environmentally influenced with minimal genetic basis. Our findings supported the multidimensionality of adolescent depression and the etiological heterogeneity of these symptom dimensions.

A Twin Study of Problematic Internet Use: Its Heritability and Genetic Association With Effortful Control

Our goal was to estimate genetic and environmental sources of influence on adolescent problematic internet use, and whether these individual differences can be explained by effortful control, an important aspect of self-regulation. A sample of 825 pairs of Chinese adolescent twins and their parents provided reports of problematic internet use and effortful control. Univariate analysis revealed that genetic factors explained 58–66% of variance in problematic internet use, with the rest explained by non-shared environmental factors. Sex difference was found, suggesting boys’ problematic internet use was more influenced by genetic influences than girls’ problematic internet use. Bivariate analysis indicated that effortful control accounted for a modest portion of the genetic and non-shared environmental variance in problematic internet use among girls. In contrast, among boys, effortful control explained between 6% (parent report) and 20% (self-report) of variance in problematic internet use through overlapping genetic pathways. Adolescent problematic internet use is heritable, and poor effortful control can partly explain adolescent problematic internet use, with effects stronger for boys. Implications for future research are discussed.

Genetic and environmental influences on adolescent rumination and its association with depressive symptoms

Rumination is an important cognitive vulnerability for adolescent and adult depression. However, little is known about the aetiological origins of rumination, as well as its association with depression. Adolescent rumination (self-report) and depressive symptoms (self- and parent-report) were assessed in 674 pairs of same-gender Chinese adolescent twins (11-17 years of age). Females accounted for 53.7 % of the sample. There were significant correlations between self-reported rumination and self-reported depression (r = 0.41), as well as parent-reported adolescent depression (r = 0.22). Genetic influences were significant and modest on all three measures, ranging from 24 % to 42 %. The three measures were also significantly influenced by shared environment, ranging from 20 % to 28 %, and non-shared environmental factors, ranging from 30 % to 56 %. Moreover, the genetic correlations between rumination and depression were significant (within-rater: r(g) = 0.99; cross-rater: r(g) = 0.59) and largely accounted for the phenotypic correlations (within-rater: 68 %; cross-rater: 77 %), while non-shared environmental correlations were also significant (within-rater: r(e) = 0.26; cross-rater: r(e) = 0.12) and accounted for the remainder of the phenotypic correlations (within-rater: 32 %; cross-rater: 23 %). The shared environmental correlations were non-significant. No significant gender and age differences were found in aetiological models. These findings suggest that rumination may be an endophenotype reflecting genetic risk for depression.

A behavioral genetic study of intrapersonal and interpersonal dimensions of narcissism

Narcissism, characterized by grandiose self-image and entitled feelings to others, has been increasingly prevalent in the past decades. This study examined genetic and environmental bases of two dimensions of narcissism: intrapersonal grandiosity and interpersonal entitlement. A total of 304 pairs of twins from Beijing, China completed the Narcissistic Grandiosity Scale and the Psychological Entitlement Scale. Both grandiosity (23%) and entitlement (35%) were found to be moderately heritable, while simultaneously showing considerable non-shared environmental influences. Moreover, the genetic and environmental influences on the two dimensions were mostly unique (92–93%), with few genetic and environmental effects in common (7–8%). The two dimensions of narcissism, intrapersonal grandiosity and interpersonal entitlement, are heritable and largely independent of each other in terms of their genetic and environmental sources. These findings extend our understanding of the heritability of narcissism on the one hand. On the other hand, the study demonstrates the rationale for distinguishing between intrapersonal and interpersonal dimensions of narcissism, and possibly personality in general as well.

Genetic and environmental etiologies of adolescent dysfunctional attitudes: a twin study

Despite the importance of dysfunctional attitudes in the development and maintenance of depression, little is known about the etiological origin of dysfunctional attitudes. The Dysfunctional Attitudes Scale for Children was administered to 674 adolescent twins derived from the Beijing Twin Study (BeTwiSt). Four hundred and thirty-nine monozygotic and 235 same-gender dizygotic twin pairs were included. Approximately 54% were females. The age range of the twins was 11-17 years. Model-fitting analyses were conducted. Biometric genetic model-fitting estimates indicated that additive genetic factors accounted for 31% (95% CI: 11%, 45%) of variance in adolescent dysfunctional attitude. The influence of shared environmental factors was small and negligible (9% [95% CI: 0%, 27%]). Non-shared environmental factors explained 60% (95% CI: 55%, 66%) of variance. Equating the estimate parameters across gender or age groups resulted in a non-significant difference of model fit, but there were trends suggesting higher heritability in females and older adolescents. Our results provide evidence for moderate heritability of dysfunctional attitudes in adolescents. Dysfunctional attitudes can be used as an endophenotype to identify risk genes for depression.

Genetic and environmental influences on depressive symptoms in Chinese adolescents

Adolescent depression is common and has become a major public health concern in China, yet little research has examined the etiology of depression in Chinese adolescents. In the present study, genetic and environmental influences on Chinese adolescent depressive symptoms were investigated in 1,181 twin pairs residing in Beijing, China (ages 11-19 years). Child- and parent-versions of the children's depression inventory were used to measure adolescents' depressive symptoms. For self-reports, genetic factors, shared environmental factors, and non-shared environmental factors accounted for 50, 5, and 45 % of the variation in depressive symptoms, respectively; for parent-reports, genetic factors, shared environmental factors, and non-shared environmental factors accounted for 51, 18, and 31 % of the variation, respectively. These estimates are generally consistent with previous findings in Western adolescents, supporting the cross-cultural generalizability of etiological model of adolescent depression. Neither qualitative nor quantitative sex differences were found in the etiological model. Future studies are needed to investigate how genes and environments work together (gene-environment interaction, gene-environment correlation) to influence depression in Chinese adolescents.

The interacting effect of the BDNF Val66Met polymorphism and stressful life events on adolescent depression is not an artifact of gene-environment correlation: evidence from a longitudinal twin study

BACKGROUND

Confounding introduced by gene-environment correlation (rGE) may prevent one from observing a true gene-environment interaction (G × E) effect on psychopathology. The present study investigated the interacting effect of the BDNF Val66Met polymorphism and stressful life events (SLEs) on adolescent depression while controlling for the rGE by two means: separating pure environmental factors (independent SLEs) from the environmental factors under partial genetic control (dependent SLEs) and adopting a prospective longitudinal design.

METHODS

A total of 780 pairs of Chinese twins, aged 11-17 years (mean = 13.6, SD = 1.8) at intake, were followed up twice. Self-reported depression symptoms at Time 1 and Time 2 were assessed by the Children's Depression Inventory (CDI). SLEs occurring between Time 1 and Time 2 were assessed by a self-reported checklist. SLEs were differentiated into independent and dependent ones and were validated by heritability analyses using twin design. The interacting effects between the BDNF Val66Met polymorphism and numbers of SLEs (total SLEs and independent SLEs) on intraindividual change of depression symptoms were examined.

RESULTS

After controlling for sex, age, age square, and Time 1 depression, both total SLEs × BDNF Val66Met genotype and independent SLEs × BDNF Val66Met genotype significantly predicted Time 2 depression. Val allele carriers (Val/Val and Val/Met) were more susceptible to the detrimental effects of stress.

CONCLUSIONS

There is a true G × E effect underlying the observed interaction between BDNF Val66Met polymorphism and environmental stress on depression.

A longitudinal investigation of the associations among parenting, deviant peer affiliation, and externalizing behaviors: a monozygotic twin differences design

Non-shared parenting and deviant peer affiliation are linked to differences in externalizing behaviors between twins. However, few studies have examined these two non-shared environments simultaneously. The present study examined the transactional roles of differential parenting (i.e., warmth and hostility) and deviant peer affiliation on monozygotic (MZ) twin differences in externalizing behaviors using a two-wave longitudinal study of twins and their parents. The sample consisted of 520 pairs of MZ twins (46.5% males, 53.5% females), with a mean age of 13.86 years (SD = 2.10) at the T1 assessment, residing in Beijing, China. The association between non-shared hostility in parenting and adolescent externalizing behaviors was mainly explained by a child-driven effect whereby the twin with a higher level of externalizing behaviors than his or her co-twin was more likely to receive more hostility from the parents. Similarly, the relationship between deviant peer affiliation and adolescent externalizing behaviors supported the selection effect whereby the twin with a higher level of externalizing behaviors than his or her co-twin was more likely to affiliate with deviant peers. The theoretical and practical implications of these findings are discussed.