Twin Study of the Relationship between Childhood Negative Emotionality and Hyperactivity/Inattention Problems.

The present study aimed to determine the genetic and environmental etiology of the association between childhood negative emotionality (NE) and hyperactivity/inattention problems (HIP) using South Korean elementary school twins (mean age = 10.19 years, SD = 1.79 years).

Genetic and environmental influences on human height from infancy through adulthood at different levels of parental education.

Genetic factors explain a major proportion of human height variation, but differences in mean stature have also been found between socio-economic categories suggesting a possible effect of environment. By utilizing a classical twin design which allows decomposing the variation of height into genetic and environmental components, we tested the hypothesis that environmental variation in height is greater in offspring of lower educated parents. Twin data from 29 cohorts including 65,978 complete twin pairs with information on height at ages 1 to 69 years and on parental education were pooled allowing the analyses at different ages and in three geographic-cultural regions (Europe, North America and Australia, and East Asia).

The South Korean Twin Registry.

The South Korean Twin Registry (SKTR) is an ongoing nationwide volunteer registry of South Korean twins and their families. Since its inception, from preschooler to young adult, twins have been registered with the SKTR and have demonstrated that relative influences of genetic and environmental factors explaining individual differences in various psychological, mental health and physical traits in South Koreans are similar to those found in many Western twin studies. Currently, studies at the SKTR focus on identification of the process of gene-by-environment interactions as well as developmental differences in genetic and environmental influences on psychological and mental health traits in South Koreans.

The Nigerian Twin and Sibling Registry: An Update.

Here we provide an update of the 2013 report on the Nigerian Twin and Sibling Registry (NTSR). The major aim of the NTSR is to understand genetic and environmental influences and their interplay in psychological and mental health development in Nigerian children and adolescents. Africans have the highest twin birth rates among all human populations, and Nigeria is the most populous country in Africa.

Parental Education and Genetics of BMI from Infancy to Old Age: A Pooled Analysis of 29 Twin Cohorts.

Objective: The objective of this study was to analyze how parental education modifies the genetic and environmental variances of BMI from infancy to old age in three geographic-cultural regions.

Methods: A pooled sample of 29 cohorts including 143,499 twin individuals with information on parental education and BMI from age 1 to 79 years (299,201 BMI measures) was analyzed by genetic twin modeling.

Results: Until 4 years of age, parental education was not consistently associated with BMI.

Religious Attendance Moderates the Environmental Effect on Prosocial Behavior in Nigerian Adolescents.

There is a growing body of literature linking religious attendance to prosocial behavior (PB). The main purposes of the present study were to estimate genetic and environmental influences on the frequency of religious attendance (FRA) and to explore whether and how FRA moderates genetic and/or environmental influences on PB. As part of the Nigerian Twin and Sibling Study, 2860 (280 monozygotic male, 417 monozygotic female, 544 dizygotic male, 699 dizygotic female, and 920 opposite-sex dizygotic) twins (mean age = 14.

Does the sex of one's co-twin affect height and BMI in adulthood? A study of dizygotic adult twins from 31 cohorts.

Background: The comparison of traits in twins from opposite-sex (OS) and same-sex (SS) dizygotic twin pairs is considered a proxy measure of prenatal hormone exposure. To examine possible prenatal hormonal influences on anthropometric traits, we compared mean height, body mass index (BMI), and the prevalence of being overweight or obese between men and women from OS and SS dizygotic twin pairs.

Methods: The data were derived from the COllaborative project of Development of Anthropometrical measures in Twins (CODATwins) database, and included 68,494 SS and 53,808 OS dizygotic twin individuals above the age of 20 years from 31 twin cohorts representing 19 countries.

Perceived Family Cohesion Moderates Environmental Influences on Prosocial Behavior in Nigerian Adolescent Twins.

Research shows that perceived family cohesion is positively related to prosocial behavior in adolescents. In this study, we investigated heritability of prosocial behavior (PB) and perceived family cohesion (FC) among Nigerian twins attending public schools in Lagos State, Nigeria (mean age = 14.7 years, SD = 1.

Genetic and environmental influences on adult human height across birth cohorts from 1886 to 1994.

Human height variation is determined by genetic and environmental factors, but it remains unclear whether their influences differ across birth-year cohorts. We conducted an individual-based pooled analysis of 40 twin cohorts including 143,390 complete twin pairs born 1886-1994. Although genetic variance showed a generally increasing trend across the birth-year cohorts, heritability estimates (0.

Twin's Birth-Order Differences in Height and Body Mass Index From Birth to Old Age: A Pooled Study of 26 Twin Cohorts Participating in the CODATwins Project.

We analyzed birth order differences in means and variances of height and body mass index (BMI) in monozygotic (MZ) and dizygotic (DZ) twins from infancy to old age. The data were derived from the international CODATwins database. The total number of height and BMI measures from 0.

The South Korean Twin Registry: an update.

The South Korean Twin Registry (SKTR) is an ongoing nation-wide volunteer registry of South Korean twins and their families, which was established in the year 2001 to understand genetic and environmental etiologies of psychological and physical traits among South Koreans. Recently, the SKTR sampling has been extended in two important ways. First, we began to recruit twins from lower socio-economic families to study interaction effects of gene by environmental context.

The Nigerian Twin and Sibling Registry.

Twin studies of Africans have been scarce although Africans have shown the highest twin birth rate in the world. As a parallel study of the South Korean Twin Registry, the Nigerian Twin and Sibling Registry (NTSR) was developed to understand causal influences on the development of cognitive abilities, personality, and mental health among Nigerians. Currently, 1,134 twins and 404 full- and half-siblings have been registered with NTSR.

Emotion and behavior: a general factor of personality from the EAS Temperament Survey and the Strengths and Difficulties Questionnaire.

The mothers of 603 pairs of 3- to 13-year-old twins in Korea completed the Emotionality, Activity, Sociability (EAS) Temperament Survey and the Strengths and Difficulties Questionnaire in reference to their twins. Principal factor analysis of the seven scales comprising these measures yielded a general factor on which all the scales had moderate to large loadings. Univariate behavioral genetic analyses showed that individual differences on this general factor could best be accounted for by additive genetic and non-shared environmental effects, with a heritability of 53%.

Feeling of cold hands and feet is a highly heritable phenotype.

The prevalence of the feeling of cold hands and feet (FCHF) is high in the general population but the etiology of FCHF is largely unknown. The aim of the present study was to explore whether the FCHF is heritable. Eight hundred and ninety-four pairs of twins completed a question about FCHF.

Sex differences in genetic and environmental influences on obsessive-compulsive symptoms in South Korean adolescent and young adult twins.

Recent molecular genetic studies provide suggestive evidence for sexual dimorphism in genetics of obsessive-compulsive disorder. However, only a few twin studies have addressed the question of sex differences in genetic and environmental contributions to variation of obsessive-compulsive symptoms. The aim of the present study was to estimate genetic and environmental influences on obsessive-compulsive symptoms in South Korean twins, with a special emphasis on sex difference.

The South Korean Twin Registry.

The South Korean Twin Registry (SKTR), previously called the Seoul Twin Family Study, is a nationwide volunteer registry of South Korean twins and their families. Since 2002, the SKTR has been updated in 4 important ways. First, continued sampling led to an increase in the number of twins.