Familial confounding of internalising symptoms and obesity in adolescents and young adults; a co-twin analysis.

BACKGROUND: Obesity and internalising disorders, including depression and anxiety, often co-occur. There is evidence that familial confounding contributes to the co-occurrence of internalising disorders and obesity in adults. However, its impact on this association among young people is unclear. Our study investigated the extent to which familial factors confound the association between internalising disorders and obesity in adolescents and young adults. SUBJECTS/METHODS: We used a matched co-twin design to investigate the impact of confounding by familial factors on associations between internalising symptoms and obesity in a sample of 4018 twins aged 16 to 27 years. RESULTS: High levels of internalising symptoms compared to low levels increased the odds of obesity for the whole cohort (adjusted odds ratio [AOR] = 3.1, 95% confidence interval [CI]: 1.5, 6.8), and in females (AOR = 4.1, 95% CI 1.5, 11.1), but not in males (AOR = 2.8 95% CI 0.8, 10.0). We found evidence that internalising symptoms were associated with an increased between-pair odds of obesity (AOR 6.2, 95% CI 1.7, 22.8), using the paired analysis but not using a within-pair association, which controls for familial confounding. Sex-stratified analyses indicated high internalising symptoms were associated with increased between-pair odds of obesity for females (AOR 12.9, 95% CI 2.2, 76.8), but this attenuated to the null using within-pair analysis. We found no evidence of between or within-pair associations for males and weak evidence that sex modified the association between internalising symptoms and obesity (likelihood ratio test p = 0.051). CONCLUSIONS: Some familial factors shared by twins confound the association between internalising symptoms and obesity in adolescent and young adult females. Internalising symptoms and obesity were not associated for adolescent and young adult males. Therefore, prevention and treatment efforts should especially address familial shared determinants of obesity, particularly targeted at female adolescents and young adults with internalising symptoms and those with a family history of these disorders.

Mental disorders and discrimination: A prospective cohort study of young twin pairs in Germany.

Background: Mental disorders and perceived discrimination share common risk factors. The association between having a mental disorder and experiencing discrimination is well-known, but the extent to which familial factors, such as genetic and shared environmental factors, might confound this association, including sex differences in familial confounding, remains unexplored. Aims: We investigated potential unmeasured familial confounding in the association between mental disorders and perceived discrimination using a matched twin study design. Method: We examined data from 2044 same-sex twin pairs (n = 4088) aged 16-25 years from the German population-based study 'TwinLife'. We applied random-effects logistic regression to within-individual and within-and-between pair models of the association between mental disorder and perceived discrimination, and used likelihood ratio tests (LRTs) to compare these models. Multivariable models were adjusted for body mass index, educational attainment, and life satisfaction. Results: There were 322 (8.1%) participants with a diagnosed mental disorder, and 15% (n = 604) of the cohort reported having experienced discrimination in the previous 12 months. Mental disorder and discrimination were associated in the adjusted within-individual model (adjusted odds ratio = 2.19, 95% confidence interval: 1.42-3.39, P<0.001). However, the within-and-between pair model showed that this association was explained by the within-pair mean (aOR = 4.24, 95% CI: 2.17-8.29, P<0.001) and not the within-pair difference (aOR = 1.26, 95% CI: 0.70-2.28, P = 0.4) of mental disorder. Therefore, this association was mostly explained by familial confounding, which is also supported by the LRTs for the unadjusted and adjusted models (P<0.001 and P = 0.03, respectively). This familial confounding was more prominent for males than females. Conclusions: Our findings show that the association between mental disorder and discrimination is at least partially explained by unmeasured familial factors. Designing family-based healthcare models and incorporating family members in interventions targeted at ameliorating mental ill-health and experiences of discrimination among adolescents may improve efficacy.

A Log File Analysis on the Validity of Partial Solutions in Figural Matrices Tests.

As a component of many intelligence test batteries, figural matrices tests are an effective way to assess reasoning, which is considered a core ability of intelligence. Traditionally, the sum of correct items is used as a performance indicator (total solution procedure). However, recent advances in the development of computer-based figural matrices tests allow additional indicators to be considered for scoring. In two studies, we focused on the added value of a partial solution procedure employing log file analyses from a computer-based figural matrices test. In the first study (n = 198), we explored the internal validity of this procedure by applying both an exploratory bottom-up approach (using sequence analyses) and a complementary top-down approach (using rule jumps, an indicator taken from relevant studies). Both approaches confirmed that higher scores in the partial solution procedure were associated with higher structuredness in participants' response behavior. In the second study (n = 169), we examined the external validity by correlating the partial solution procedure in addition to the total solution procedure with a Grade Point Average (GPA) criterion. The partial solution procedure showed an advantage over the total solution procedure in predicting GPA, especially at lower ability levels. The implications of the results and their applicability to other tests are discussed.

How did the beginnings of the global COVID-19 pandemic affect mental well-being?

The present study aims to investigate longitudinal changes in mental well-being as well as the role of individual differences in personality traits (Big Five) and the level of Personality Organisation during the first lockdown of the COVID-19 pandemic in Germany. Overall, 272 adults (Mage= 36.94, SDage= 16.46; 68.62% female, 23.45% male, 0.69% non-binary) took part in our study with four weekly surveys during the lockdown as well as a follow-up one month after restrictions were lifted. To analyse the development of mental well-being during and shortly after the first lockdown in Germany latent growth curve models (LGCM) were calculated. The considered facets of well-being differ by their trajectory. Additionally, results suggest that the lockdown did not affect all facets to the same extent. While Life Satisfaction decreases in the short term as a reaction to the lockdown, Stress and Psychological Strain were reduced after the second week of contact restrictions. When adding personality characteristics, our results showed that Neuroticism and Conscientiousness were the two dimensions associated most strongly with SWB during the first month of the pandemic. Thus, our research suggests that personality traits should be considered when analysing mental well-being.

Genetics, parenting, and family functioning-What drives the development of self-control from adolescence to adulthood?

OBJECTIVE: Self-control is a meaningful predictor of crucial life outcomes. Knowingly, genes contribute substantially to differences in self-control, but behavioral genetic findings are often misinterpreted regarding environmental influences. Therefore, we reinvestigate the heritability of self-control as well as potential environmental influences, namely parenting and a chaotic home environment. METHOD: We used cross-sectional and longitudinal data from the German twin family study TwinLife (N = 3354 individuals), structured in a multicohort design in which 13-, 19-, and 25-year-old twins rated their self-control, parents' behavior, and home environment. RESULTS: Results showed increasing mean levels and 1-year stabilities for self-control accompanied by substantial genetic influences, increasing particularly from ages 19 to 25 (53% to 76%). While chaotic home environments and negative parenting were phenotypically associated with lower self-control, twin difference models revealed that differences in these individually perceived "environments" directly predicted self-control differences (ß = -0.16 to -0.28) within families when controlling for genetic and environmental similarities. CONCLUSIONS: In addition to the genetic anchoring of self-control, results indicate that environmental factors such as negative family environments are meaningful and depend on individual perceptions within families. Interventions for enhancing self-control should, therefore, rely on individual perspectives rather than objective characteristics of home environments.

Development and Validation of the Open Matrices Item Bank.

Figural matrices tasks are one of the most prominent item formats used in intelligence tests, and their relevance for the assessment of cognitive abilities is unquestionable. However, despite endeavors of the open science movement to make scientific research accessible on all levels, there is a lack of royalty-free figural matrices tests. The Open Matrices Item Bank (OMIB) closes this gap by providing free and unlimited access (GPLv3 license) to a large set of empirically validated figural matrices items. We developed a set of 220 figural matrices based on well-established construction principles commonly used in matrices tests and administered them to a sample of N = 2572 applicants to medical schools. The results of item response models and reliability analyses demonstrate the excellent psychometric properties of the items. In the discussion, we elucidate how researchers can already use the OMIB to gain access to high-quality matrices tests for their studies. Furthermore, we provide perspectives for features that could additionally improve the utility of the OMIB.

Test Preparation in Figural Matrices Tests: Focus on the Difficult Rules.

It is well documented that training the rules employed in figural matrices tests enhances test performance. Previous studies only compare experimental conditions in which all or no rules were trained and therefore ignore the particular influence of knowledge about the easy and difficult rules. With the current study, we wanted to provide some first insights into this topic. Respondents were assigned to four groups that received training for no rules, only the easy rules, only the difficult rules, or for all rules. The results show that a training only for the difficult rules was more effective than the other trainings. This applies also to performance in the easy rules that were actually not part of the training. A possible explanation for this finding is a facilitation of the solution process that is primarily driven by knowledge about the difficult rules. In conclusion, our results demonstrate that taking differences between the rules into account may provide a deeper understanding of the effects of trainings for figural matrices tests.

Measuring Anxiety in Older Adults: Development, Diagnostic Accuracy, and Preliminary Validation of a Short-Form of the German Geriatric Anxiety Scale (GAS-G-SF).

Anxiety symptoms and anxiety disorders are highly prevalent among older adults, and are associated with considerable distress, functional impairment, and burden. Also, there is growing need for brief instruments to measure anxiety symptoms in primary care and geriatric medical settings. Therefore, the current study focuses on the development and psychometric evaluation of a short-form of the Geriatric Anxiety Scale (GAS-G), a well-established anxiety instrument for use with older adults. Study 1 draws on the original data from the GAS-G validation study (N = 242) to develop the short-form (GAS-G-SF) and determines whether the results replicate with the short-form. Study 2 extends the validation of the GAS-G-SF to a clinical sample (N = 156; 62 patients with heart disease, 94 patients with Parkinson's disease). Overall, the GAS-G-SF showed promising psychometric properties in terms of internal consistency and validity. Also, the GAS-G-SF showed good discriminatory power based on receiver operating characteristic curve analysis in both studies. These results support the utility of the GAS-G-SF as a brief assessment measure for anxiety.

The German Twin Family Panel (TwinLife).

The German Twin Family Panel (TwinLife) is a German longitudinal study of monozygotic and dizygotic same-sex twin pairs and their families that was designed to investigate the development of social inequalities over the life course. The study covers an observation period from approximately 2014 to 2023. The target population of the sample are reared-together twins of four different age cohorts that were born in 2009/2010 (cohort 1), in 2003/2004 (cohort 2), in 1997/1998 (cohort 3) and between 1990 and 1993 (cohort 4). In the first wave, the study included data on 4097 twin families. Families were recruited in all parts of Germany so that the sample comprises the whole range of the educational, occupational and income structure. As of 2019, two face-to-face, at-home interviews and two telephone interviews have been conducted. Data from the first home and telephone interviews are already available free of charge as a scientific use-file from the GESIS data archive. This report aims to provide an overview of the study sample and design as well as constructs that are unique in TwinLife in comparison with previous twin studies - such as an assessment of cognitive abilities or information based on the children's medical records and report cards. In addition, major findings based on the data already released are displayed, and future directions of the study are presented and discussed.

SES-of-Origin and BMI in Youth: Comparing Germany and Minnesota.

Increasing obesity is a world-wide health concern. Its most commonly used indicator, body mass index (BMI), consistently shows considerable genetic and shared environmental variance throughout life, the latter particularly in youth. Several adult studies have observed less total and genetically influenced variance with higher attained SES. These studies offer clues about sources of the 'obesity epidemic' but analogous youth studies of SES-of-origin are needed. Genetic and environmental influences and moderating effects of SES may vary in countries with different health policies, lifestyles, and degrees/sources of social inequality, offering further clues to the sources of the obesity epidemic. We examined SES-of-origin moderation of BMI variance in the German TwinLife study's cohorts assessed around ages 5, 11, 17, and 23-24, and in the Minnesota Twin Family Study's (MTFS) 11- and 17-year-old birth cohorts assessed longitudinally around ages 11, 17, and 23-24, comparing male and female twins and their parents. Age for age, both sexes' means and variances were greater in MTFS than in TwinLife. We observed that SES generally moderated genetic influences, more strongly in females, similar to most adult studies of attained-SES moderation of BMI. We interpreted differences in our SES-of-origin observations in light of inevitably-missing covariance between SES-of-origin and BMI in the models, mother-father and parent-offspring BMI correlations, and parental attained-SES-BMI correlations. We suggest that one source of the present obesity epidemic is social change that amplifies expression of genes both constraining SES attainment and facilitating weight gain.

Does the heritability of cognitive abilities vary as a function of parental education? Evidence from a German twin sample.

A well-known hypothesis in the behavioral genetic literature predicts that the heritability of cognitive abilities is higher in the presence of higher socioeconomic contexts. However, studies suggest that the effect of socioeconomic status (SES) on the heritability of cognitive ability may not be universal, as it has mostly been demonstrated in the United States, but not in other Western nations. In the present study we tested whether the importance of genetic and environmental effects on cognitive abilities varies as a function of parental education in a German twin sample. Cognitive ability scores (general, verbal, and nonverbal) were obtained on 531 German twin pairs (192 monozygotic, 339 dizygotic, ranging from 7 to 14 years of age; Mage = 10.25, SD = 1.83). Data on parental education were available from mothers and fathers. Results for general cognitive ability and nonverbal ability indicated no significant gene x parental education interaction effect. For verbal ability, a significant nonshared environment (E) x parental education interaction was found in the direction of greater nonshared environmental influences on verbal abilities among children raised by more educated parents.

Is the Correlation between Storage Capacity and Matrix Reasoning Driven by the Storage of Partial Solutions? A Pilot Study of an Experimental Approach.

Working memory capacity (WMC) and reasoning abilities-as assessed by figural matrices tests-are substantially correlated. It is controversially discussed whether this correlation is only caused by controlled attention or also by storage capacity. This study aims at investigating storage of partial solutions as a possible mechanism by which storage capacity may contribute to solving figural matrices tests. For this purpose, we analyzed how an experimental manipulation of storage demands changes the pattern of correlations between WMC and performance in a matrix task. We manipulated the storage demands by applying two test formats: one providing the externalization of partial solutions and one without the possibility of externalization. Storage capacity was assessed by different types of change detection tasks. We found substantial correlations between storage capacity and matrices test performance, but they were of comparable size for both test formats. We take this as evidence that the necessity to store partial solutions is not the limiting factor which causes the association between storage capacity and matrices test. It is discussed how this approach can be used to investigate alternative mechanisms by that storage may influence performance in matrices tests.

How distinctive are morningness and eveningness from the Big Five factors of personality? A meta-analytic investigation.

This study explores relations between measures of individuals' circadian preferences and the Big Five. To this end, we compared a model of circadian preferences that acknowledges morningness (M) and eveningness (E) as separate dimensions to that of a model that places M and E on a single continuum (M-E). Analyses of 620 correlations from 44 independent samples (N = 16,647) revealed weak to modest relations between both dimensions of circadian preferences and the Big Five personality traits. The strongest observed relation was found between Conscientiousness and M (ρ = .37). In the next step, regression analyses revealed that personality traits accounted for between 10.9% and 16.4% of the variance in circadian preferences. Of all the Big Five dimensions, Conscientiousness exhibited the strongest unique relation with M (ß = .32), E (ß = -.26), and M-E (ß = .32). Extraversion and Openness exhibited moderate unique relations with E (ß = .23 and ß = .17, respectively), whereas relations with M (ß = .00 and ß = .04), and M-E (ß = -.05 and ß = -.06) were relatively weak. Neuroticism exhibited a modest unique and negative relation with M (ß = -.16), and Agreeableness was largely unrelated to all circadian preference variables. To determine whether these findings translated into anything of applied significance, we explored relations between circadian preference and academic performance. M and E incremented slightly over the Big Five factors in predicting grade-point average. Theoretical and practical implications of these findings are discussed. (PsycINFO Database Record

Internet addiction and its facets: The role of genetics and the relation to self-directedness.

A growing body of research focuses on problematic behavior patterns related to the use of the Internet to identify contextual as well as individual risk factors of this new phenomenon called Internet addiction (IA). IA can be described as a multidimensional syndrome comprising aspects such as craving, development of tolerance, loss of control and negative consequences. Given that previous research on other addictive behaviors showed substantial heritability, it can be expected that the vulnerability to IA may also be due to a person's genetic predisposition. However, it is questionable whether distinct components of IA have different etiologies. Using data from a sample of adult monozygotic and dizygotic twins and non-twin siblings (N=784 individuals, N=355 complete pairs, M=30.30years), we investigated the magnitude of genetic and environmental influences on generalized IA as well as on specific facets such as excessive use, self-regulation, preference for online social interaction or negative consequences. To explain the heritability in IA, we further examined the relation to Self-Directedness as potential mediating source. Results showed that relative contributions of genetic influences vary considerable for different components of IA. For generalized IA factors, individual differences could be explained by shared and non-shared environmental influences while genetic influences did not play a role. For specific facets of IA and private Internet use in hours per week, heritability estimates ranged between 21% and 44%. Bivariate analysis indicated that Self-Directedness accounted for 20% to 65% of the genetic variance in specific IA facets through overlapping genetic pathways. Implications for future research are discussed.

What Drives the Development of Social Inequality Over the Life Course? The German TwinLife Study.

The German twin family study 'TwinLife' was designed to enhance our understanding of the development of social inequalities over the life course. The interdisciplinary project investigates mechanisms of social inequalities across the lifespan by taking into account psychological as well as social mechanisms, and their genetic origin as well as the interaction and covariation between these factors. Main characteristics of the study are: (1) a multidimensional perspective on social inequalities, (2) the assessment of developmental trajectories in childhood, adolescence, and young adulthood in a longitudinal design by using (3) a combination of a multi-cohort cross-sequential and an extended twin family design, while (4) capturing a large variation of behavioral and environmental factors in a representative sample of about 4,000 German twin families. In the present article, we first introduce the theoretical and empirical background of the TwinLife study, and second, describe the design, content, and implementation of TwinLife. Since the data will be made available as scientific use file, we also illustrate research possibilities provided by this project to the scientific community.

Correction: The Role of Nature and Nurture for Individual Differences in Primary Emotional Systems: Evidence from a Twin Study.

[This corrects the article DOI: 10.1371/journal.pone.0151405.].

The Role of Nature and Nurture for Individual Differences in Primary Emotional Systems: Evidence from a Twin Study.

The present study investigated for the first time the relative importance of genetics and environment on individual differences in primary emotionality as measured with the Affective Neuroscience Personality Scales (ANPS) by means of a twin-sibling study design. In N = 795 participants (n = 303 monozygotic twins, n = 172 dizygotic twins and n = 267 non-twin full siblings), moderate to strong influences of genetics on individual differences in these emotional systems are observed. Lowest heritability estimates are presented for the SEEKING system (33%) and highest for the PLAY system (69%). Further, multivariate genetic modeling was applied to the data showing that associations among the six ANPS scales were influences by both, a genetic as well as an environmental overlap between them. In sum, the study underlines the usefulness of the ANPS for biologically oriented personality psychology research.

University Students' Satisfaction with their Academic Studies: Personality and Motivation Matter.

Although there is consensus about the importance of students' satisfaction with their academic studies as one facet of academic success, little is known about the determinants of this significant outcome variable. Past research rarely investigated the predictive power of multiple predictors simultaneously. Hence, we examined how demographic variables, personality, cognitive and achievement-related variables (intelligence, academic achievement), as well as various motivational constructs were associated with three different dimensions of satisfaction (satisfaction with study content, satisfaction with the conditions of the academic program, satisfaction with the ability to cope with academic stress) assessed approximately 2 years apart. Analyzing data of a sample of university students (N = 620; M age = 20.77; SD age = 3.22) using structural equation modeling, our results underline the significance of personality and motivational variables: Neuroticism predicted satisfaction with academic studies, but its relevance varied between outcome dimensions. Regarding the predictive validity of motivational variables, the initial motivation for enrolling in a particular major was correlated with two dimensions of subsequent satisfaction with academic studies. In contrast, the predictive value of cognitive and achievement-related variables was relatively low, with academic achievement only related to satisfaction with the conditions of the academic program after controlling for the prior satisfaction level.