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Twin Registries Worldwide: An Important Resource for Scientific Research
Abstract and Figures
Twins can provide unique opportunities to study causal influences on variation in human behaviors, development, and diseases. During the past 10 years, the number of twin registries has increased rapidly across the globe and we thought it timely to bring these to the attention of our readership. In this special issue, we invited papers on twin registries and cohorts from 28 countries representing five continents. Subjects covered include how to establish and maintain twin registries, accurately assess zygosity, collect biospecimens, and other important issues related to twin studies. This special issue shows that over 1.5 million twins and their families are participating in twin studies worldwide. Research interests will be highlighted, with the aim of fostering collaborative research.
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... The traditional epidemiologic methods of studying psychiatric genetics involve investigation of families, twins and adoptees [1]. Data from these designs help to improve the accuracy of risk communication to patients and their relatives, clarify the effects of genes and environment, assist in classification and diagnosis, and may be useful in identifying at-risk family members for possible prevention and early intervention, with a view to shortening the duration of untreated disease [1,2]. Despite the usefulness of these traditional methods, there is a dearth of data in sub-Saharan Africa (SSA) with regard to family genetic epidemiological data on severe mental disorders (SMDs). ...
... Five studies that met the inclusion criteria were identified in only one out of the 46 countries in SSA, namely Nigeria (n = 5) [11][12][13][14][15]. The characteristics of the studies included were as follows: family history method (n = 3) [11][12][13], mixed family history and family study method (n = 2) [2] and twin and adoption studies (n = 0). Summary of the results of the identified articles is presented in Table 1. ...
... Despite SSA having the highest rate of twin birth rate in the world [16], the authors did not find any twin study of major mental disorders in the region. However, on a positive note, the literature reported on two twin registers newly established in SSA, namely Guinea-Bissau and Nigeria [2,17]. Both registries aim to study children and adolescent twins; however, the focus of the two differ. ...
Abstract
Purpose: The traditional genetic epidemiological studies are necessary to improve accurate risk communication to service users and their families. This scoping review aimed to describe the volume and scope of existing research evidence on family, twin and adoption studies of severe mental disorders (SMDs) in SSA. This is with a view to identifying gaps in the literature and the adequacy of data for a systematic review and meta-analysis.
Methods: Literature search was done for all original peer-reviewed research articles on the topic in SSA using PubMed and MEDLINE. Publications included were peer-reviewed original articles, irrespective of their quality, carried out in the region from the 1970s till 9th March, 2022, which were available in English or translated to English. Case reports, abstracts, and studies among populations living outside the region were excluded.
Results: A total of five studies that met the inclusion criteria across the 46 countries in the region were identified. Of the three thematic areas of focus, only family studies on SMDs had research work in SSA. These studies provided evidence of familial clustering of SMDs in SSA. There were no twin and adoption studies on SMDs in the region. However, the review noted the establishment of two twin registries in Guinea-Bissau and Nigeria. A huge gap exists in the area of twin and adoption studies on SMDs in SSA.
Conclusion: The volume of research evidence on traditional family genetic studies of SMDs is grossly inadequate to consider a systematic review in SSA. We have suggested studies to remedy the situation.
Keywords: Adoption; Family; Severe mental disorders; Studies; Sub-Saharan Africa; Twin.
... Multisite data collection and data sharing have long been common in statistical genetics (Haworth et al., 2013;Hur & Craig, 2013). In earlier stages of the discipline, in which techniques for direct, large-scale inspection of the genome were not yet available, heritability had to be estimated indirectly through twin and family studies (Plomin et al., 2016), which require gathering data from individuals in rather rare groups and configurations. ...
Consensus on standards for evaluating models and theories is an integral part of every science. Nonetheless, in psychology, relatively little focus has been placed on defining reliable communal metrics to assess model performance. Evaluation practices are often idiosyncratic and are affected by a number of shortcomings (e.g., failure to assess models’ ability to generalize to unseen data) that make it difficult to discriminate between good and bad models. Drawing inspiration from fields such as machine learning and statistical genetics, we argue in favor of introducing common benchmarks as a means of overcoming the lack of reliable model evaluation criteria currently observed in psychology. We discuss a number of principles benchmarks should satisfy to achieve maximal utility, identify concrete steps the community could take to promote the development of such benchmarks, and address a number of potential pitfalls and concerns that may arise in the course of implementation. We argue that reaching consensus on common evaluation benchmarks will foster cumulative progress in psychology and encourage researchers to place heavier emphasis on the practical utility of scientific models.
Twins provide a unique opportunity for epidemiological research by investigating the role of genetic predisposition vs. environmental factors. The Chinese National Twin Registry (CNTR) is relatively young compared with those of western countries. Twin research, however, grows fast in China. The CNTR has registered 61,566 twin pairs including 31,705 monozygotic and 28,591 dizygotic pairs. These twins are important resources for examining genetic and environmental contributions to common diseases in China. With the development of novel technologies, twin studies will have substantial value in exploring the molecular mechanisms of complex diseases with multiple genetic and/or environmental risk factors. This review will introduce history of twin research, the value of twin studies, twin registries in the world, and the advances of twin research in exploring the etiology of chronic diseases using Chinese twins, including heritability estimation of single trait, genetic correlation among multiple phenotypes, as well as the modification of heritability and multi-omics studies particularly focusing on DNA methylation, DNA methylation age, and metabolomics. Despite the progress made in twin studies of China, there is still a long way to go for the CNTR in exploring the mysteries of the human organism in the future. At last, the short-term and long-term goals of the CNTR will be presented.KeywordsTwin studiesChronic diseaseEnvironmentGeneticsChina
For more than 65 years, twin registries have contributed to our knowledge about genetic and environmental influences on all aspects of human life. Since the establishment of the first twin registry in 1954 in Denmark, many twin registries have been founded worldwide. Here, we provide an overview of the spread of twin registries across the world. While the oldest and largest twin registries reside in Europe, twin registries also have a strong presence in the United States, Australia, and East Asia. New registries have more recently been established in Africa, the Middle East, and Latin America, ensuring that twin registries are present across six continents. Twin registries vary widely in their inclusion criteria: while some registries still focus on the twin pair, a number of registries have started to also include family members of twins. The total scope of twin registries is large, representing combined more than 1.3 million individuals. The longitudinal character of twin registries in combination with extensive data collection, by surveys but also via registry linkages and experimental settings, means that they represent a treasure trove of data. In addition, while at its roots twin registries used the difference in genetic similarity for monozygotic and dizygotic twins to estimate the heritability of traits, many twin registries now also collect genotypic and epigenetic information. The maintenance and expansion of twin registries across the world will continue to contribute to the enhancement of our knowledge of genetic and environmental causes of complex human behaviors and health.
Twin research is integral in epidemiological research to understand the role of genetics and the environment related to health and disease. Despite the methodological advantages, the use of twins as participants in interventional randomized controlled trials (RCTs) are limited. Cotwin designs can increase statistical power while also having the added advantage of involving smaller sample sizes. Twin RCTs may also control for potential confounding factors such as genetic makeup and age. This chapter discusses the value of twins in interventional research and the advantages and limitations of conducting twin RCTs.
Objective
Childhood obesity is a major health concern worldwide. Previous studies have explored the relationship between obesity and gut microbiota. However, the results from such studies remain contradictory.Methods
In the present nested case-control study, based on a twin birth cohort study, the relationship between gut microbiota diversity and overweight/obesity in 1- and 6-month-old infants was explored. Twins were enrolled when one child had normal weight and the other child was overweight/obese at six months old. For both infants, stool samples were collected at 1 and 6 months of age. Finally, 12 twins were enrolled in the study. The gut microbiota was identified by 16S rRNA gene sequencing in the V3–V4 area. Six of the twins were monozygotic.ResultsThe results revealed that the microbiota communities of monozygotic twins were similar to those of dizygotic twins. The relative abundance (RA) of microbiota of 1-month-old twins was significantly higher than that of 6-month-old twins. However, the microbiota diversity of 1-month-old twins was significantly lower than that of 6-month-old twins. In addition, 6-month-old twins had significantly higher RA levels of Bifidobacterium and Lachnospiracea incertae sedis than 1-month-old twins. The 6-month-old group had significantly lower RA levels of Veillonella, Klebsiella, Akkermansia, Streptococcus, or Staphylococcus than the 1-month-old group. At six months, the RA level of Clostridium sensu stricto was higher in the overweight/obesity group than the normal-weight group.Conclusion
These findings imply that changes in gut microbiota diversity during infancy may contribute to the development of obesity in early infancy.
Zusammenfassung
Nach dem Zweiten Weltkrieg wurden weltweit Zwillingskohorten aufgebaut, die inzwischen ca. 1,5 Mio. Zwillinge umfassen und zwischen 1950 und 2012 über 2748 Zwillingsstudien hervorgebracht haben. Diese Zahl steigt jedes Jahr um weitere 500 bis 1000. Die Unterrepräsentanz deutscher Zwillingsstudien in diesen Datenbanken lässt sich nicht allein durch den Missbrauch medizinischer Forschung im Nationalsozialismus erklären. Entwicklung und Ausbau großer Zwillingskohorten sind ethisch und datenschutzrechtlich eine Herausforderung. Zwillingskohorten ermöglichen jedoch die Langzeit- und Echtzeiterforschung vieler medizinischer Fragestellungen; und die Zwillingsstudien tragen auch nach der Entschlüsselung des Humangenoms erheblich zur Beantwortung der Frage nach Anlage oder Umwelt als mögliche Erkrankungsauslöser bei.
Derzeit gibt es 2 deutsche Zwillingskohorten: die biomedizinische Kohorte HealthTwiSt mit ca. 1500 Zwillingspaaren und TwinLife , eine soziologisch-psychologische Kohorte mit ca. 4000 Zwillingspaaren. Daneben gibt es krankheitsspezifische Kohorten. 2016 startete das TwinHealth -Konsortium der Medizinischen Fakultät der Universität Tübingen mit dem Ziel, eine forschungsoffene und nachhaltige Zwillingsforschung am Standort Tübingen zur Bearbeitung unterschiedlicher Fragestellungen zu etablieren.
Der Artikel bietet mithilfe einer systematischen Literaturrecherche und einer medizinhistorischen Betrachtung einen Überblick über die weltweite und nationale Entwicklung von Zwillingsstudien und -datenbanken der letzten 100 Jahre. Anhand der Tübinger TwinHealth -Initiative beleuchtet er den Aufbau eines Zwillingskollektivs und dessen juristische, ethische und Datenschutzaspekte.
Classical twin and family designs can be applied to examine the contribution of genetic and environmental influences to variation in epigenetic marks. Such models can be extended to allow for more in-depth questions, such as: How much of the variation in DNA methylation is explained by methylation Quantitative Trait Loci (QTLs)? Does the contribution of genetic or environmental influences differ between males and females or between younger and older individuals? Does methylation level at CpG site X have a causal effect on trait Y and vice versa, or is the association driven by genetic pleiotropy? In this chapter, we discuss twin designs that allow to address these questions. First, we describe models that incorporate genetic relationships based on genome-wide SNP data and the application of such models to DNA methylation data from adult twins and family members. Second, we discuss the value of an integration of Mendelian Randomization (MR) with the classical twin design.
As most common oral conditions and diseases have complex genetic and environmental etiologies, twin and family studies have been utilized for decades to explore the relative contribution of each to disease susceptibility. In the omic-era they offer exciting potential to utilize emerging scientific and analytical techniques to give valuable insight into disease mechanisms and develop novel approaches to disease prevention and management. This chapter will review the application of twin and family studies to understanding risk, etiology, disease mechanisms and epigenetics and several aspects of oral health, including childhood dental caries, periodontal disease, and craniofacial development; and identify future directions for research.
Accurate determination of zygosity and chorionicity is essential in all multiple maternities. The parents and the multiples themselves ask it. It is of medical importance and now considered as a prerequisite in several domains of twin research, especially when perinatal data are analysed. It helps the multiples and their parents and teachers to ascertain identity. The methods are briefly described and a plea is made to obstetricians and paediatricians to use them systematically at the time of birth.
Accurate determination of zygosity and chorionicity is essential in all multiple maternities. The parents and the multiples themselves ask it. It is of medical importance and now considered as a prerequisite in several domains of twin research, especially when perinatal data are analysed. It helps the multiples and their parents and teachers to ascertain identity. The methods are briefly described and a plea is made to obstetricians and paediatricians to use them systematically at the time of birth.
Twin research offers the greatest power for the genetic analysis of complex multifactorial traits and diseases in humans. Modern twin analyses extend beyond the classical twin study for estimating the heritability of a trait. The human genome project can fulfil its promises only after functional characterisation of single genes in the context of genetic background and environment. Twin research can make a major contribution in that regard. Twin research is greatly facilitated by the willingness, motivation, cooperation, and generosity of the participants and their families. A second important aspect is the availability of twin registries that serve as a resource for genetic epidemiology. Currently, there is no systematic overview of the twin collections worldwide. This special issue will help to overcome the limited accessibility of this resource by providing basic information on most of the existing twin registers. Furthermore, an additional goal is to facilitate collaboration between registers. Some basic principles, potentials, and problems will be exemplified by my personal experience in the Berlin Twin Study.
- J C Flanagan
Flanagan, J. C. (1962). Project TALENT. Applied Psychology,
11, 3-14.
Twin Registers as a global resource for genetic research
- Busjahn
Busjahn, A., & Hur, Y.-M. (2006). Twin Registers as a global
resource for genetic research. Twin Research and Human
Genetics, 9, 6.
The biology of twinning in man
- M G Bulmer
Bulmer, M. G. (1970). The biology of twinning in man. Oxford,
UK: Clarendon Press.