scholarly journals Twin studies of psychosis and the genetics of cerebral asymmetry

1999 ◽  
Vol 175 (5) ◽  
pp. 399-401 ◽  
Author(s):  
T. J. Crow
Keyword(s):  
General Population ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Weight Of Evidence ◽  
Perinatal Complications ◽  
Cerebral Asymmetry ◽  
Psychotic Illness ◽  
Dizygotic Twins ◽  
Increased Risk ◽  
Issue Reports

Kläning (1999, this issue) reports that dizygotic twins are at increased risk of schizophrenia relative to the general population. Any departure from the first assumption of twin studies that the illness has the same origin in twins as it does in the general population might tell us something about aetiology. Kläning's expectation that monozygotic twins would be at increased risk because such pairs are at increased risk of perinatal complications was not confirmed, adding to the weight of evidence that such complications are unrelated to the origins of psychotic illness. The contrary finding that dizygotic twins are at increased risk draws attention to the nature of dizygotic twinning. Is there something about this process that yields a clue to the origins of psychosis?

scholarly journals Dentofacial Characteristics among Monozygotic and Dizygotic Twin Pairs from a Unique Village of Twins in South India: A Descriptive Cross-sectional Study

2017 ◽  
Vol 03 (01) ◽  
pp. 025-028
Author(s):  
Praveen Jodalli ◽  
Ganesh Panchmal ◽  
Vinej Somaraj ◽  
Shafees Koya
Keyword(s):  
South India ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Cross Sectional ◽  
Factors Influencing ◽  
Dizygotic Twins ◽  
Cast Analysis ◽  
Dental Cast

Abstract Aim: To assess the dentofacial characteristics of a mystery village of twins in South India. Materials and methods: A descriptive cross-sectional study was carried out among of 22 twin pairs (10 monozygotic twins and 12 dizygotic twins). The evaluation was done in terms of height, weight, dentofacial profile, and occlusion status based on anthropometric, photographic, and dental cast analysis. Results: Data obtained upon analysis of anthropometric measurements, photographic data, and dental cast evaluation revealed a set of characteristics peculiar to the twins of this unique village. Conclusion: Twin studies are a fascinating method of research because of their ability to correctly isolate a characteristic and determine its impact, especially in terms of dentofacial characteristics. Clinical significance: Twin research design involving the comparison of variables among monozygotic (identical) and dizygotic (fraternal) twins is a method by which researchers quantify and classify the contribution of genes and other extraneous factors influencing heredity on the dentofacial complex and dentition.

Genetic factors in anorexia nervosa

1999 ◽  
Vol 14 (4) ◽  
pp. 189-198 ◽  
Author(s):  
A. Kipman ◽  
P. Gorwood ◽  
M.C. Mouren-Siméoni ◽  
J. Adès
Keyword(s):  
Anorexia Nervosa ◽  
Genetic Factors ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Vulnerability Factors ◽  
Adoption Studies ◽  
Complex Disorder ◽  
Dizygotic Twins ◽  
The One ◽  
Familial Environment

SummaryAnorexia nervosa is a severe and complex disorder with incompletely known vulnerability factors. It is generally recognized that anorexia nervosa is a familial disorder, but the majority of twin studies have shown that the concordance rate for monozygotic twins is higher (on average 44%) than for dizygotic twins (on average 12.5%). This difference in concordance rates shows that genetic factors, more than common familial environment, may explain why the `anorexia nervosa' phenotype runs in families. In order to estimate the heritability in the broad sense of anorexia nervosa according to published familial and twin studies, we first assessed the intrapair correlation between monozygotic and dizygotic twins, and secondly calculated the deviation threshold of relatives of affected probands from the relative mean. In this review, we obtained an estimation of the heritability at 0.72 according to all published controlled familial studies (six references quoted in MEDLINE®), and 0.71 for all published twin studies (59 references quoted in MEDLINE®). This estimation is close to the ones previously proposed, between 0.5 and 0.8.Familial and twin studies may also help to define the boundaries of the phenotype, shedding light on the complex relationship between anorexia nervosa on the one hand, and bulimia nervosa, mood disorders, and alcoholism on the other. Demonstrating the importance of genetic factors in anorexia nervosa, and more specifically for anorexia of the restrictive type, requires not only prospective and adoption studies (which are still lacking), but also genetic polymorphisms analyses, which began very recently.

scholarly journals Primary Biliary Cirrhosis: Family Stories

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Daniel Smyk ◽  
Evangelos Cholongitas ◽  
Stephen Kriese ◽  
Eirini I. Rigopoulou ◽  
Dimitrios P. Bogdanos
Keyword(s):  
Primary Biliary Cirrhosis ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Cholestatic Liver Disease ◽  
Biliary Cirrhosis ◽  
Family Stories ◽  
Immune Mediated ◽  
Increased Risk ◽  
Environmental Component ◽  
High Concordance

Primary biliary cirrhosis (PBC) is a chronic immune-mediated cholestatic liver disease of unknown aetiology which affects mostly women in middle age. Familial PBC is when PBC affects more than one member of the same family, and data suggest that first-degree relatives of PBC patients have an increased risk of developing the disease. Most often, these familial clusters involve mother-daughter pairs, which is consistent with the female preponderance of the disease. These clusters provide evidence towards a genetic basis underlying PBC. However, clusters of nonrelated individuals have also been reported, giving strength to an environmental component. Twin studies have demonstrated a high concordance for PBC in monozygotic twins and a low concordance among dizygotic twins. In conclusion, studies of PBC in families clearly demonstrate that genetic, epigenetic, and environmental factors play a role in the development of the disease.

Greater occurrence of schizophrenia in dizygotic but not monozygotic twins

1999 ◽  
Vol 175 (5) ◽  
pp. 407-409 ◽  
Author(s):  
Ulla Kläning
Keyword(s):  
General Population ◽  
Record Linkage ◽  
Monozygotic Twins ◽  
Young Cohort ◽  
Case Register ◽  
Dizygotic Twins ◽  
The Difference ◽  
Direction Opposite ◽  
First Admission ◽  
Danish Twin

BackgroundA previous study demonstrated a higher rate of first hospitalisation for schizophrenia in twins than in singletons.AimsTo compare the schizophrenia rates in monozygotic twins, dizygotic twins and the general population.MethodThrough record linkage between the Young Cohort of the Danish Twin Register and the Danish Psychiatric Case Register, the rate of schizophrenia in’ monozygotic and dizygotic twins and the rate in the general population were compared.ResultsThe rate of first admission to hospital for schizophrenia in dizygotic twins was 40% greater than that in the general population. The rate in monozygotic twins was not increased. The difference between the rates in mono- and dizygotic twins was statistically significant (P < 0.001)ConclusionsThis result is surprising and is in the direction opposite to that expected, suggesting new possibilities in the study of risk factors.

scholarly journals How to face the association between tobacco and psychosis?

10.3823/2427 ◽  
2017 ◽  
Vol 10 ◽  
Author(s):  
Raphael Tavares Dantas ◽  
Wanderley Gonçalves Cordeiro Júnior ◽  
Marcial Moreno Moreira ◽  
Lídia Coelho do Nascimento Santos ◽  
Sidney Medeiros De Oliveira ◽  
...  
Keyword(s):  
General Population ◽  
Key Words ◽  
Psychotic Disorder ◽  
Age Of Onset ◽  
Age At Onset ◽  
Mean Difference ◽  
First Episode ◽  
Psychotic Illness ◽  
Increased Risk ◽  
Key Words Tobacco

Evidences suggest an association between tobacco and psychosis. However, the reasons why people with psychosis have a higher tendency to smoke than the general population are not yet clear. Recently, Gurillo et al. reported that daily use of tobacco is associated with an increased risk of psychotic disorder and an earlier age of onset of psychotic illness. His study also calculated a significant mean difference in age at onset, expressed in years, and estimated the prevalence of smoking in people with their first episode of psychosis. According to this and other findings, it could be said that the causes of the smoking-schizophrenia association are complex and cannot be explained solely as a result of some aspect of schizophrenia. Thus, new studies in this area are needed, as well as strategies that look for the monitoring of smoking effects in order to reduce it among individuals with schizophrenia. Key-words: Tobacco, Psychosis, Illness.

scholarly journals On The Influence of Genetic Factors on the Formation of Homosexuality by Data of Twin Studies

2019 ◽  
Keyword(s):  
Sexual Orientation ◽  
Genetic Factors ◽  
Dominant Role ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Correct Selection ◽  
Genetic Determination ◽  
Dizygotic Twins

Results of twin studies are presented; these demonstrate that in a number of cases genetic effects can play a role of mild predisposing factors for the development of homosexuality, but the main part in its formation is accounted for by psychological and social factors. The opinion that genetic factors play the only and dominant role in the genesis of homosexuality does not hold water due to the fact that if it were so then their concordance for homosexuality in monozygotic twins would be 100 %, but it is not observed in reality. The studies conducted with the correct selection of examinees revealed 20 % of the concordance for homosexuality in male monozygotic twins and 24 % in female ones (Bailey, J.M., et al. Genetic and environmental influences on sexual orientation and its correlates in an Australian twin sample. J. Pers. Soc. Psychol. 78(3), 524‑536). The use of Holzinger’s formula for analyzing the obtained numerical findings demonstrated that in the above case the proportion between heritable and environmental factors for male persons was 0.2 (20 %) versus 0.8 (80 %), for female persons it being 0.15 (15 %) versus 0.85 (85 %). Earlier twin studies (Bailey, J.M., Pillard, R.C. (1991). A genetic study of male sexual orientation. Arch. Gen. Psychiatry. 48(12), 1089–1096) revealed that their concordance for homosexuality in siblings (biological brothers, who are not twins) was lower than in adopted brothers (9.2 % versus 11 %), it contradicting to the idea of genetic determination of same-sex attraction. Moreover, attention is also attracted by the fact that dizygotic male twins demonstrated a significantly higher concordance for homosexuality than siblings (22 % versus 9.2 %). But it is known that dizygotic twins, like siblings, have on an average only 50 % of common genes. If there were genetic determination, such differences would not exist; the revealed difference demonstrates environmental effects, since it is evident that family upbringing of dizygotic twins is much more similar. Also it is necessary to pay attention to the fact that the rate of homosexuality in adopted homosexual brothers (11 %) considerably exceeded recent estimations of the part of homosexuals in the general population and was actually equal to the value for siblings, once again convincingly demonstrating a significant role of the environment in the formation of sexual orientation. We should not also ignore the fact that upbringing of monozygotic twins is even more similar than that of dizygotic ones; this phenomenon can cause their larger concordance for homosexuality.

scholarly journals VALIDATION OF ZYGOSITY ASSESSMENT BY A SELF-REPORT QUESTIONNAIRE IN A SAMPLE OF ADULT SERBIAN TWINS

2019 ◽  
Vol 11 (4) ◽  
pp. 419-432 ◽  
Author(s):  
Petar Čolović ◽  
Bojan Branovački ◽  
Dragana Zgonjanin Bosić
Keyword(s):  
Cross Validation ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Self Report ◽  
Correct Identification ◽  
Dizygotic Twins ◽  
Zygosity Questionnaire ◽  
Small Set ◽  
Adult Twins ◽  
Physical Resemblance

Validation of a twin zygosity-estimating questionnaire, The Questionnaire of Twins’ Physical Resemblance, created by Oniszczenko et al. and used in European and Serbian twin studies, was carried out on a sample of 222 pairs (176 monozygotic, 46 dizygotic) of adult twins (average age 24.6). Four discriminant functions, use of different sets of indicators (zygosity questionnaire items), were applied in order to obtain the most correct and accurate estimates of zygosity. The first function was a predefined function used in European twin studies, the following two functions contained sets of 18 and 24 freely estimated indicators respectively, while the last one utilized the items with most consistent contributions to zygosity prediction. The analytic procedure included cross-validation, whereby the sample was randomly split into two subsamples, comprising 107 and 115 twin pairs. The results pointed to successful (over 90% correct) identification of monozygotic twins, and sizeably lower correctness in identifying dizygotic twins. Overall correctness of estimation exceeded 90%, with the small set of best-performing indicators. The results encourage questionnaire estimation of zygosity, and raise the issue of improving the classification procedure in dizygotic twins.

scholarly journals Co-aggregation and heritability of organ-specific autoimmunity: a population-based twin study

2020 ◽  
Vol 182 (5) ◽  
pp. 473-480 ◽  
Author(s):  
Jakob Skov ◽  
Daniel Eriksson ◽  
Ralf Kuja-Halkola ◽  
Jonas Höijer ◽  
Soffia Gudbjörnsdottir ◽  
...  
Keyword(s):  
Autoimmune Diseases ◽  
Atrophic Gastritis ◽  
Genetic Factors ◽  
Monozygotic Twins ◽  
Twin Studies ◽  
Addison’S Disease ◽  
Addison's Disease ◽  
Graves Disease ◽  
Dizygotic Twins ◽  
Organ Specific

Objective Co-aggregation of autoimmune diseases is common, suggesting partly shared etiologies. Genetic factors are believed to be important, but objective measures of environmental vs heritable influences on co-aggregation are absent. With a novel approach to twin studies, we aimed at estimating heritability and genetic overlap in seven organ-specific autoimmune diseases. Design Prospective twin cohort study. Methods We used a cohort of 110 814 twins to examine co-aggregation and heritability of Hashimoto’s thyroiditis, atrophic gastritis, celiac disease, Graves’ disease, type 1 diabetes, vitiligo and Addison’s disease. Hazard ratios (HR) were calculated for twins developing the same or different disease as compared to their co-twin. The differences between monozygotic and dizygotic twin pairs were used to estimate the genetic influence on co-aggregation. Heritability for individual disorders was calculated using structural equational modeling adjusting for censoring and truncation of data. Results Co-aggregation was more pronounced in monozygotic twins (median HR: 3.2, range: 2.2–9.2) than in dizygotic twins (median HR: 2.4, range: 1.1–10.0). Heritability was moderate for atrophic gastritis (0.38, 95% CI: 0.23–0.53) but high for all other diseases, ranging from 0.60 (95% CI: 0.49–0.71) for Graves’ disease to 0.97 (95% CI: 0.91–1.00) for Addison’s disease. Conclusions Overall, co-aggregation was more pronounced in monozygotic than in dizygotic twins, suggesting that disease overlap is largely attributable to genetic factors. Co-aggregation was common, and twins faced up to a ten-fold risk of developing diseases not present in their co-twin. Our results validate and refine previous heritability estimates based on smaller twin cohorts.

Cholestasis: A Prospective Study of Perinatal Outcomes and Time to Symptom Improvement

2020 ◽  
Author(s):  
Casey S. Yule ◽  
Denisse S. Holcomb ◽  
Alexandria C. Kraus ◽  
Charles E.L. Brown ◽  
Donald D. McIntire ◽  
...  
Keyword(s):  
Preterm Birth ◽  
General Population ◽  
Survival Curve ◽  
Mode Of Delivery ◽  
Perinatal Outcomes ◽  
Symptom Improvement ◽  
Perinatal Complications ◽  
Spontaneous Preterm Birth ◽  
Severity Of Disease ◽  
Increased Risk

Objective Although intrahepatic cholestasis of pregnancy (ICP) remains poorly understood, there are several perinatal complications associated with this condition. This study aimed to examine perinatal outcomes of women with ICP, evaluate outcomes according to severity of disease, and monitor time to symptom improvement following diagnosis. Study Design It involves a prospective, observational study of women with ICP at a single institution. Women with new-onset pruritus without rash were referred to a high-risk obstetrics clinic and evaluated with fasting total bile acids (TBA). Laboratory-confirmed ICP was defined as fasting TBA ≥10 µmol/L. Following diagnosis, a standardized protocol was utilized, including treatment with ursodeoxycholic acid (UDCA). Perinatal outcomes were compared amongst those with and without ICP, and to the general population. Women with ICP were further analyzed based on maximum TBA: 10 to 39, 40 to 99, and ≥100 µmol/L. A Kaplan-Meier survival curve was used to analyze time to symptom improvement. Results A total of 404 patients were evaluated and 212 (52%) were diagnosed with ICP. The mean gestational age at diagnosis was 34.1 ± 3.3 weeks. When comparing those with ICP to those not confirmed, and to the general population, there were no differences in age, parity, mode of delivery, preeclampsia, or stillbirth (p > 0.05). Preterm birth was significantly associated with ICP (p < 0.01). This relationship was significant across increasing severity of TBA (p < 0.01) and persisted when examining rates of spontaneous preterm birth (p < 0.01). All women with fasting TBA ≥40 µmol/L delivered preterm due to premature rupture of membranes or spontaneous labor. Time to symptom improvement after diagnosis was over 2 weeks on average; however, this time increased with worsening severity of disease. Conclusion Despite treatment with UDCA, women with ICP are at increased risk for spontaneous preterm birth, and this risk significantly increased with severity of disease. Although not significant, a trend exists between increasing time to symptom improvement and worsening severity of disease. Key Points

The Season of Birth of Schizophrenic, Neurotic and Psychiatrically Normal Twins

1982 ◽  
Vol 141 (2) ◽  
pp. 186-190 ◽  
Author(s):  
Kenneth S. Kendler
Keyword(s):  
Research Council ◽  
National Research Council ◽  
Twin Studies ◽  
Season Of Birth ◽  
Perinatal Complications ◽  
National Academy Of Sciences ◽  
Twin Registry ◽  
Increased Risk ◽  
Academy Of Sciences ◽  
Normal Twin

SummaryThe quarter of birth of 536 schizophrenic, 1,991 neurotic and 12,085 psychiatrically normal twin pairs from the National Academy of Sciences-National Research Council Twin Registry was compared. When either all twin pairs, or only monozygotic or dizygotic twin pairs, were considered, no significant differences were found in the quarter of birth between the 3 groups. No difference in quarter of birth was found for twin pairs concordant versus discordant for schizophrenia. Despite the increased risk for intrauterine and perinatal complications in twin births, schizophrenic twins appear (at least) to be no more vulnerable than schizophrenic singletons to the seasonal gestation and birth-related insults which probably underlie the seasonality in schizophrenic births. Controlling for season of birth probably has little effect on the results of twin studies of schizophrenia.

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