The Swedish Twin Registry (abbreviated STR) is a twin registry based at the Karolinska Institutet in Stockholm, Sweden. Originally established in the 1960s, it is the largest twin registry in the world. It is widely used for medical research, with about thirty active research projects using data from the study as of 2019. [1] As of 2012, it contained a total of 194,000 twins, 75,000 of whom were of a known zygosity. [2] In principle, it contains records of every twin born in Sweden since 1886. [3]
The Swedish Twin Registry was first developed in the late 1950s to study the effects of environmental factors, like alcohol and tobacco, on chronic disease risk while controlling for potential genetic confounding factors. When the registry was first started, researchers contacted every parish in Sweden to obtain records of multiple births between 1886 and 1925. The researchers then used this information to develop a list of potential twins, whose actual twin status was verified in 1959. In 1960 and 1961, a questionnaire asking about demographic and health-related information was sent to all living same-sex twins that had been identified in Sweden at the time. [4] The registry was officially established in 1961. [5] Additional questionnaires were sent out in 1963 and 1967, and select twin pairs also responded to a further questionnaire in 1970. [4] By 1970, it was estimated that the STR had included 95% of all twins born in Sweden from 1886 to 1925. [6] More recently, the STR has obtained records of twin births in Sweden from the country's National Board of Health and Welfare. In 2004, the registry began inviting all identified nine-year-old twins in the country to participate in its Child and Adolescent Twin Study in Sweden (CATSS). [2]
The Swedish Twin Registry initially consisted of three cohorts of twins: those born in 1886–1925, those born in 1926–58, and those born in 1959–90. [4] More recently, STR researchers have contacted and screened twins born from 1959 to 1985. Over 25,000 of these twins were later enrolled in the Study of Twin Adults: Genes and Environment (STAGE), which was the first STR-based study to use an online questionnaire. [2] [3]
Twin studies are studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders. Twin research is considered a key tool in behavioral genetics and in related fields, from biology to psychology. Twin studies are part of the broader methodology used in behavior genetics, which uses all data that are genetically informative – siblings studies, adoption studies, pedigree, etc. These studies have been used to track traits ranging from personal behavior to the presentation of severe mental illnesses such as schizophrenia.
The Karolinska Institute is a research-led medical university in Solna within the Stockholm urban area of Sweden and one of the foremost medical research institutes globally. The Nobel Assembly at the Karolinska Institute awards the Nobel Prize in Physiology or Medicine. The assembly consists of fifty professors from various medical disciplines at the university. The current vice-chancellor of Karolinska Institute is Annika Östman Wernerson, who took office in March 2023.
The Minnesota Center for Twin and Family Research is a series of behavioral genetic longitudinal studies of families with twin or adoptive offspring conducted by researchers at the University of Minnesota. It seeks to identify and characterize the genetic and environmental influences on the development of psychological traits.
The State Institute for Racial Biology was a Swedish governmental research institute founded in 1922 with the stated purpose of studying eugenics and human genetics. It was the most prominent institution for the study of "racial science" in Sweden. It was located in Uppsala. In 1958, it was renamed to the State Institute for Human Genetics and is today incorporated as a department of Uppsala University.
The Twins Early Development Study (TEDS) is an ongoing longitudinal twin study based at King's College London. The main goal of TEDS is to use behavioural genetic methods to find out how nature (genes) and nurture (environments) can explain why people differ with respect to their cognitive abilities, learning abilities and behaviours. The study was founded by Robert Plomin in 1994, and it includes participants from over 15,000 families. The original participants were identified from birth records among the set of twins born in the United Kingdom from 1994 to 1996. They were first assessed at the age of two and regularly re-assessed thereafter.
Hellin's law, also called Hellin-Zeleny's law, is an empirical observation in demography that the approximate rate of multiple births is one n-tuple birth per 89n-1 singleton births: twin births occur about once per 89 singleton births, triplets about once per 892, quadruplets about once per 893, and so on.
Jan Staffan Normark is a Swedish physician, microbiologist and infectious disease researcher. He grew up in Umeå and was awarded his Ph.D. at Umeå University in 1971. At the end of the 1970s, he was one of the first Swedish scientists to use the new genetic engineering tools in infection-related research. In 1980, he was made a professor at Umeå University, then the university's youngest. 1989 he was recruited as professor of molecular microbiology to Washington University in St. Louis. 1993 he returned to Sweden as professor of infectious disease control, in particular clinical bacteriology, at Karolinska Institutet. From 1999 to 2005 he served as the Executive Director of the Swedish Foundation for Strategic Research (SSF). In 2008 he was active at Umeå University to build up a research group within bioinformatics and infection research. Much of his research in the 2000s have focussed on pneumococcus.
Fritiof Stig Sjöstrand was a Swedish physician and histologist born in Stockholm. He started his medical education at Karolinska Institutet in 1933, where he received his Ph.D. Karolinska Institutet in 1944. Sjöstrand worked as an assistant at the department of pharmacology, where he first had used polarization microscopy, he first heard about the new method of electron microscopy in 1938, within which he would become a pioneer. Manne Siegbahn at the Nobel Institute for Physics had planned to build an electron microscope in Sweden, and Sjöstrand got involved in the project to explore its use in medical research. The main challenge was to produce sufficiently thin samples, and Sjöstrand's method for producing ultrathin tissue samples was published in Nature in 1943. However, it seemed that research based on electron microscopy would be too time-consuming for a Ph.D. thesis, so his 1944 thesis was based on fluorescence spectroscopy. In 1947-1948, he received a scholarship to further study electron microscopy at Massachusetts Institute of Technology's Department of Biology. Back in Sweden, he received funding to build up an electron microscopy research laboratory. In 1959, Sjöstrand was both offered a position as professor of histology at Karolinska Institutet, and as professor at University of California, Los Angeles (UCLA). He chose UCLA, because conditions for research and funding were better there.
TwinsUK, also known as TwinsUK Registry, is the biggest UK adult registry of twins in the United Kingdom, ages 16 to 98 to study the genetic and environmental aetiology of age related complex traits and diseases. Established in 1993, it is based at King's College London with an intent of aiding genetic research. The registry is used to connect researchers to volunteers.
Björn Gustaf Oscar Floderus was a Swedish physician and botanist, specializing in the willow genus Salix. He was the son of educator Manfred Mustafa Floderus (1832–1909).
Adoption studies typically compare pairs of persons, e.g., adopted child and adoptive mother or adopted child and biological mother, to assess genetic and environmental influences on behavior. These studies are one of the classic research methods of behavioral genetics. The method is used alongside twin studies to identify the roles of genetics and environmental variables that impact intelligence, and behavioral disorders.
Aurelio José Figueredo is an American evolutionary psychologist. He is a professor of psychology, Family Studies and Human Development at the University of Arizona, where he is also the director of the Ethology and Evolutionary Psychology Laboratory. He is also a member of the interdisciplinary Center for Insect Science at the University of Arizona. His major areas of research interest are the evolutionary psychology and behavioral development of life history strategy, cognition, sex, and violence in human and nonhuman animals, and the quantitative ethology and social development of insects, birds, and primates. He is known for his research on personality, such as a 1997 study in which he and James E. King developed the Chimpanzee Personality Questionnaire to measure the Big Five personality traits in chimpanzees.
The Vietnam Era Twin Registry is a twin registry containing 7,369 male-male twin pairs who served in the United States Armed Forces during the Vietnam War. As of 2013, it is one of the largest national adult twin samples in the United States. All of the twins in the registry were born between 1939 and 1955. Though it was originally formed to study the effects of military service on health, it has since been widely used to study the role of genetics in many specific mental and physical illnesses.
Douglas F. Easton FMedSci is a British epidemiologist who conducts research on the genetics of human cancers. He is Professor of Genetic Epidemiology and Centre for Cancer Genetic Epidemiology at the University of Cambridge. He founded Cambridge's Cancer Research UK Genetic Epidemiology Unit in 1995, and was a Principal Research Fellow there from 2001 to 2011. He is a Professorial Fellow of Homerton College, Cambridge.
Nancy L. Pedersen is an American genetic epidemiologist. She is Professor of Genetic Epidemiology and the leader of the Swedish Adoption/Twin Study of Aging (SATSA) at the Karolinska Institutet in Stockholm, Sweden. She is known for her research on human twins, much of which is based on the Swedish Twin Registry. This has included research on the genetic basis of Alzheimer's disease and self-confidence.
James Shields was a Scottish psychiatric geneticist and twin researcher. In the 1960s, he worked with Irving Gottesman on a twin study of schizophrenia at the Medical Research Council Psychiatric Genetics Unit at Maudsley Hospital in London, England. This study, known as the Maudsley twin study, is now considered a landmark in the field. He had previously begun working for Eliot Slater at Maudsley after serving in the United Kingdom's Royal Artillery during World War II. He was a fellow of the Eugenics Society and the International Society for Twin Studies. After Shields died in 1978, Gottesman founded the annual James Shields Award for Lifetime Contributions to Twin Research in his honor.
The Danish Twin Registry, also known as the Danish Twin Register, is a twin registry aiming to include records of all twins in the country of Denmark. Established in 1954, it is the oldest nationwide twin registry in the world. It initially included only twins born in Denmark from 1870 to 1910, but it has since grown to include almost all twins born in the country since 1870. It includes over 86,000 twin pairs, making it one of the largest twin registries in the world, and it is considered to be representative of the general population of Denmark. It includes biological data and repeated measurements from the same subjects, as well as information from other national registers in Denmark.
Danuta Elizabeth Wasserman is a professor of psychiatry and suicidology at Karolinska Institutet in Sweden. She is a public mental health and medical educator. She is currently the President of the World Psychiatric Association (WPA).
Ronald S. Wilson was an American clinical psychologist and behavioral geneticist. At the time of his death, he was a Professor of Pediatrics at the University of Louisville and director of the Louisville Twin Study, as well as president of the Behavior Genetics Association. He joined the faculty of the University of Louisville School of Medicine in 1965 and became director of the Louisville Twin Study there in 1967; he held both positions from then until his death. Originally an associate professor at the University of Louisville, he was promoted to the rank of full professor there in 1971. He was a fellow of the American Association for the Advancement of Science and the American Psychological Association, as well as a member of the Society for the Study of Human Biology and a founding fellow of the International Society for Twin Studies, of which he served as vice president from 1980 to 1983. In 1979, he received the American Association for the Advancement of Science's Socio-Psychological Prize, and in 1980, he received the James Shields Award from the International Society for Twin Studies. He was elected president-elect of the Behavior Genetics Association in 1984. He died of a heart attack while playing tennis on November 16, 1986.
Hugo Zeberg is a Swedish physician and academic. He is an Assistant Professor in the Department of Physiology and Pharmacology at Karolinska Institutet.