Two Italian twin registers are described, the Register of Italian Twin Athletes (RITA) and the Twin Register of Rome (TERRY), developed in recent years at the newly established University of Sport and Movement Sciences of Rome-Foro Italico (IUSM). Ascertainment procedures, database, applications and current prospects are outlined, along with their research focus, which mainly consists of epidemiological and clinical research on the determinants of sport performance as well as on the role of genetic factors versus lifestyle, especially physical activity, in health and aging.

The present study compared bereavement responses of 325 monozygotic (MZ) and 176 dizygotic (DZ) adolescent and adult twins following the loss of their co-twins. A subset of twins completed the Grief Experience Inventory using a retrospective time frame, while a second subset completed it using a current time frame. It was hypothesized that MZ twins (in both retrospective and current groups) would report higher levels of grief-related behavior than DZ twins, consistent with Hamilton's (1964) concept of inclusive fitness. Discriminant function and profile analyses yielded supportive findings, but only for the retrospective MZ and DZ twin comparisons. Females in both groups expressed higher levels of bereave-ment-related behavior than males. Findings are discussed with reference to theoretical aspects of grief and mourning.

Families with twins occasionally confront unique problems warranting considerable professional attention. The possibility that twins may be less likely to be admitted to private schools of their choice, due to reduced financial contributions from family members, was recently raised. Specifically, two twin children have two sets of grandparents, while two non-twin children have four sets of grandparents; thus, schools would profit more highly by admitting non-twins. This sets the stage for reviewing steps that some universities and businesses have taken to offset the financial burdens of rearing multiples. Next, a research review of four twin studies follows. Findings on gluten sensitivity, tremors, communicative adaptability and serological differences are summarized. A tour of a fascinating twin exhibit at the Teylers Museum, in the Netherlands, concludes this column.

The unique opportunity given by the “fiscal code”, an alphanumeric identification with demographic information on any single person residing in Italy, introduced in 1976 by the Ministry of Finance, allowed a database of all potential Italian twins to be created. This database contains up to now name, surname, date and place of birth and home address of about 1,300,000 “possible twins”. Even thought we estimated an excess of 40% of pseudo-twins, this still is the world's largest twin population ever collected. The database of possible twins is currently used in population-based studies on multiple sclerosis, Alzheimer's disease, celiac disease, and type 1 diabetes. A system is currently being developed for linking the database with data from mortality and cancer registries. In 2001, the Italian Government, through the Ministry of Health, financed a broad national research program on twin studies, including the establishment of a national twin registry. Among all the possible twins, a sample of 500,000 individuals are going to be contacted and we expect to enrol around 120,000 real twin pairs in a formal Twin Registry. According to available financial resources, a sub sample of the enrolled population will be asked to donate DNA. A biological bank from twins will be then implemented, guaranteeing information on future etiological questions regarding genetic and modifiable factors for physical impairment and disability, cancers, cardiovascular diseases and other age related chronic illnesses.

Cultural beliefs about the nature of multiples appear in the mourning practices of many civilizations. Ethnographic literature suggests common themes that echo modern concepts. Many societies viewed twins as fragile, likely to die without preferential or meticulously equal treatment. A shared soul between twins is a common tenet, and the death of one is often felt to herald the other's prompt demise. The close relationship between multiples influences funerary rites. Honor, fear and mysticism are often evident in rituals. Twin infanticide was widely practiced, yet mourning customs were still observed. Many peoples recognize the special status of multiples and their families after one, two or more die.

We describe subject recruitment and research results from the Osaka University Aged Twin Registry (OUATR). The research focus of OUATR is the genetic and environmental contributions to physical-cognitive-mental aging which we examined in Japanese twins in later adulthood. Within this large-scale registry (12,000 pairs) of oriental twins born between 1900 and 1935, approximately 10% of participants are MZ twins reared apart from early childhood. Two hundred and fifty pairs have had comprehensive medical examinations, including various blood chemical panels, lymphocyte subtests, WAIS (Wechsler Adult Intelligence Scale), and urine analysis. The future foci of this study are primarily on longevity, decline of cognitive functions with aging, bio-physiological functions, lifestyle and behavior genetics, and psycho-spiritual functions.

Many twin researchers occasionally encounter twin pairs displaying unusual physical, medical or behavioral traits. Unfortunately, these interesting cases are often unreported because they do not fit in easily with ongoing projects. However, these “odd cases” may suggest new hypotheses, new designs or entirely new projects. In this paper, I argue in favor of publishing case studies of exceptional twins, and refer to several large scale studies inspired by such reports. Several informative case studies are then summarized: DZ twins discordant for hyperinsulinism, DZ twins born after ICSI, “simultaneous madness in twins, and sixteenth century conjoined twins. The article concludes with a review of parenting twin pandas.

Only recently has the special bereavement associated with the loss of a twin been generally recognised. With the notable exception of Joan Woodward, few have written on the subject. We, therefore, offer a shortened version of a paper written nearly 30 years ago. George Engel was himself a lone twin as well as being an eminent psychiatrist and psychoanalyst in the United States. The length of the paper precludes reprinting the totality but we hope readers will be encouraged to seek out the original published in The International Journal of Psycho-analysis in 1975, Vol 56 part 1, 23–40 .

Several studies have explored the impact of marital bereavement on mortality, while increasing emphasis has recently been placed on genetic factors influencing longevity — in this paper, we study the impact of losing the spouse and losing the co-twin, for twins aged 50 to 70. We use data from the Danish Twin Registry and the Population Register of Denmark for the period 1968 through 1999. Firstly, we use survival analysis to study mortality after the death of the spouse or the co-twin. We find that the risk of dying is highest in the first year after the death of the spouse, as well as in the second year after the death of the co-twin. We then use event history analysis techniques to show that there is a strong impact of the event ‘losing the co-twin' even after controlling for age, sex and zygosity and that this effect is significantly higher in the second year of bereavement. The effect is similar for men and women, and it is higher for monozygotic twins. The latter confirms the influence of genetic factors on survival, while the mortality trajectory with a peak in the second year after the death of the co-twin is consistent with the existence of a twin bereavement effect.

The Seoul Twin Family Study seeks to investigate genetic and environmental influences on the development of cognitive abilities and other psychological traits among children and adolescents in Seoul, South Korea. In November, 2001 with the assistance of the Seoul Metropolitan Office of Education, we began to solicit all private and public schools in Seoul to obtain names, addresses, and telephone numbers of the twins enrolled in schools in Seoul. The vast majority of the recruited twins were between 6 and 18 years old. The recruited twins and their non-twin siblings and parents will undergo comprehensive assessment of cognitive abilities, interests, daily activities, personality, and familial and non-familial environments. We plan to reassess the twins and their families every two years as the twins progress through major changes that characterize childhood, adolescence, and adulthood. In addition, medical records of the twins during the prenatal period will be examined to determine the effects of intrauterine environment on individual differences in cognitive abilities and other psychological traits. We also plan to undertake molecular genetic studies to identify genes involved in specific cognitive abilities.

The Korean Twin Registry is the first nationwide twin study in Korea. We compiled 154,783 twin pairs from existing nationwide data sources, mainly from address and national health insurance data. The coverage of this registry was almost complete for the twins born since 1970, but less complete as age increased, so that there were only 990 pairs who were born before 1930. The twins' health examination (N = 54,390 persons) and questionnaire (N = 44,546 persons) results were incorporated into the registry, yielding 12,894 and 9074 concordantly informative pairs. Morbidity and mortality outcomes have been followed up since 1990, for most diseases. For preliminary analysis of complex diseases, we selected ventricular septal defects (VSD) in young twins, stomach and colorectal cancers in adult twins. We identified 353 VSDs, 284 stomach cancers, and 116 colorectal cancers among twins. The prevalence rates of cancers, but not that of VSD, were lower in twins than those in population. The difference in the cancer prevalence was marked for twins born before 1926, implying some degree of selection. Like-sex (LS) twins showed familial recurrence risks (λLS) of 41.2 for VSD and 22.4 for colorectal cancers, and 1.74 for stomach cancers. For opposite-sex (OS) twins, we could estimate λOS of 19.8 for VSD only. These results were compatible with previous studies for VSD and colorectal cancers, but not for stomach cancers. Despite the strength in size, availability of health outcomes, and some lifestyle and basic laboratory data, we need accurate zygosity information to improve the validity of the results.

The primary foci of twin research have been on twins as a biological phenomenon, on the management of medical complications of twin pregnancy and birth and on the study of individual differences and development by psychologists and geneticists for whom twins provide a powerful research tool. The twin relationship — twinship — has received less research attention, including the aspect of bereavement which may occur at any stage of life. This paper presents some findings from a qualitative study that used grounded theory methodology to explore the nature of twinship especially issues relevant to psychological counselling with twins. Fourteen participants were interviewed in-depth about their understanding and experience of twinship. Participants were selected who had a rich knowledge and experience of twinship and of therapeutic work. Segments of transcribed interviews were constantly compared to describe and elaborate frequently repeated concepts in the data. Two of the main themes of discernment, the core category of the theory of twinship, are described. These are ‘defining boundaries’ and ‘managing ambiguity’. Aspects of these as experienced by twins are discussed in the light of current psychological theories about bereavement.

In 1986 we began The Netherlands Twin Register (NTR) by recruiting young twins and multiples a few weeks or months after birth. Currently we register around 50% of all newborn multiples in The Netherlands. Their parents receive a questionnaire at registration and afterwards when the children are 2, 3, 5, 7, 10 and 12 years of age. Teachers are asked to rate the behavior of the children at ages 7, 10 and 12 years. Adolescent and young-adult twins were recruited through City Councils in the early 1990s. These twins, their parents and siblings participate in longitudinal survey studies that include items about health, fertility, lifestyle, addiction, personality and psychopathology, religion, socioeconomic status, and educational attainment. The total number of twins and multiples registered with the NTR is currently over 60,000. Subgroups of twins and siblings take part in studies of cognitive development, brain function and neuropsychological indices of attention processes, and molecular genetic studies of classical and behavioral cardiovascular risk factors. DNA samples are currently collected in selected twin families for two large linkage studies, which aim to find QTLs for anxious depression and for nicotine addiction. Sisters who are mothers of DZ twins contribute DNA samples for a linkage study of DZ twinning. Large cohorts of phenotyped family members from the general population are very valuable for genetic epidemiological studies and permit selection of informative families for gene finding studies.

In this exploratory study of 15 families with a twin-pair, of which one has an intellectual disability, the Nijmegen Questionnaire on Childrearing Situations (NQCS) was used to ask mothers about their perceptions and experiences of parenting. An interview with the mothers was done to understand the initial stages of coping with this double problem: educating a twin-pair and a child with an intellectual disability. Four groups of mothers were identified, depending on whether they accepted the intellectual disability of their child and/or whether they perceived their children as a twin-pair or not. Finally, some critical questions for further research and management were formulated.

The Norwegian Twin Registers include several sets of population-based sub-registers, and covers twin pairs born between 1895 and today. Except for the missing birth years 1960 to 1967, the register is almost complete. Most of the register contains information about both same-sexed and opposite-sexed twin pairs, except for twin pairs born between 1946 and 1960, where only same-sexed twins are registered. In a substantial part of the register, information about zygosity is obtained, mainly by a mailed questionnaire and in some cases supported by DNA testing. These are the birth years 1915 to 1960 and the birth years 1967 to 1979. Zygosity information is further obtained in the different twin studies derived from the twin register. In 1990 the whole register was made available in a computerized form. Several twin studies have been derived from the different parts of the register. In this article, studies from the two earliest parts of the register are reviewed and grouped by recruitment specifics. Finally, future plans for the register and twin studies are discussed.

With the dramatic increase in the incidence of higher-order multiple pregnancies, more and more women are advised to consider undergoing multifetal reduction. However, little is known about the woman's experience of making the decision to undergo or forgo reduction. This study explored the experiences of seven women in making this decision and to identify any effects of it. Vivid descriptions emerged of multiple levels of bereavement. Several participants lamented that nothing occurred naturally in their pregnancies, from conception right through delivery and life with multiples.

We invited bereaved twins, parents of twins and carers to describe some of their personal experiences. We are grateful to all of them for their brave candour. We gave extra space to Kathy's story about the impacts of the loss of her own twin because it vividly illustrates the profound connections twinship can generate. Similarly we thought the cruelly long and complex saga of the life and death of Maxine's twins could help understanding of the distressing repercussions that often attend the low birth weight and prematurity that are so common amongst multiple births.