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Twin Pairs (twin + pair)
Kinds of Twin Pairs Terms modified by Twin Pairs Selected AbstractsTwin deliveries and place of birth in NSW 2001,2005AUSTRALIAN AND NEW ZEALAND JOURNAL OF OBSTETRICS AND GYNAECOLOGY, Issue 5 2009Charles S. ALGERT Background:, Twin pregnancies have an elevated risk of adverse outcomes, particularly preterm twins. Aims:, Describe the distribution of twin deliveries by hospital level, the associated perinatal and maternal morbidity, and determine predictors of perinatal morbidity and urgent transfer to a neonatal intensive care unit. Methods:, Longitudinally linked New South Wales delivery and hospital records for the years 2001,2005 were used to identify perinatal and maternal morbidity/mortality in twin pregnancies. Regression analysis was used to examine predictive factors, including birth hospital volume. Results:, At , 32 weeks, 88.1% of twins were delivered in tertiary referral hospitals. By 34,35 weeks, only 39.7% of twins were delivered in tertiary units. Gestational age was the primary predictor of perinatal morbidity/mortality. Perinatal morbidity/mortality and maternal morbidity were lowest for deliveries at 38 weeks. There was no evidence that planned caesarean section at , 38 weeks was protective against perinatal morbidity/mortality. There was an increased risk of perinatal morbidity/mortality (odds ratio (OR) = 2.22) for twins delivered at 33,35 weeks gestation at hospitals with < 500 deliveries per annum, and an increased risk of urgent neonatal transfer (OR = 2.06). Twin pairs for whom there was a , 20% discordance in birthweight had an increased risk of morbidity/mortality at 36,38 weeks (OR = 1.79). Conclusions:, Both infant and maternal morbidity increase from 39 weeks gestation. Delivery of twins before 36 weeks at smaller hospitals (< 500 deliveries per annum) should be avoided. A twin pregnancy where there is a , 20% difference in estimated fetal weights should be considered for referral to a tertiary obstetric unit. [source] Influence of mode of delivery on neonatal mortality in the second twin, at and before termBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 12 2008A Herbst Design, To study the association between mode of delivery and neonatal mortality in second twins. To study the association between caesarean delivery and mortality with minimum bias of the indication for the operation, we wanted to compare the outcome of second twins delivered by caesarean due to breech presentation of the sibling with vaginally delivered second twins in uncomplicated pregnancies. Setting, Sweden, 1980,2004 Population, Twins born during 1980,2004 were identified from the Swedish Medical Birth Registry. Twin pairs delivered by caesarean due to breech presentation of the first twin, and vaginally delivered twins with the first twin in cephalic presentation were included. Pregnancies with antepartum complications were excluded. Methods, Odds ratios and 95% CI were calculated using multiple logistic regression analyses, adjusting for year of birth, maternal age, parity and gestational age. Main outcome measures, Neonatal mortality. Results, Compared with second-born twins delivered vaginally, second-born twins delivered by caesarean (for breech presentation of the sibling) had a lower risk of neonatal death (adjusted OR 0.40; 95% CI 0.19,0.83). The decreased risk after caesarean delivery was significant for births before 34 weeks (2.1 versus 9.0%; adjusted OR 0.40; 95% CI 0.17,0.95). After 34 weeks, neonatal mortality was low in both groups (0.1 and 0.2%, respectively), and the difference was not statistically significant (adjusted OR 0.42; 95% CI 0.10,1.79). Conclusions, Neonatal mortality is lower for the second twin after caesarean delivery at birth before 34 weeks. At term, mortality is low irrespective of delivery mode. [source] Craniorachischisis and Heterotaxia with Heart Disease in Twins: Link or Change Nature?CONGENITAL HEART DISEASE, Issue 5 2010Sebastiano Bianca MD ABSTRACT Craniorachischisis is a rare neural tube defect in which both acrania and a complete schisis of the vertebral column are present. Heterotaxy results from failure to establish normal left,right asymmetry during embryonic development and is characterized by a variable group of congenital anomalies that include complex cardiac malformations and situs inversus or situs ambiguous. We report a diamniotic twin pregnancy with two malformed fetuses affected one by craniorachischisis and the other by heterotaxya with paired right-sided viscera, asplenia, and complex congenital heart disease. The occurrence of severe congenital anomalies in both members of the twin pair implies a strong influence of genetic factors. At present, the genetic basis determining the different phenotypes observed in our twins is unknown. Our case with the simultaneous presence of both midline and laterality defects in twins supports the hypothesis that the midline plays a critical role in establishing left,right asymmetry in the body and that a mutation in a gene responsible for both heterotaxy and midline defects may be strongly supposed. [source] Genetic Probes of Three Theories of Maternal Adjustment: II.FAMILY PROCESS, Issue 3 2001Environmental Influences, Genetic This is the first report of the Twin Mom Study, an investigation of three hypotheses concerning influences on maternal adjustment. These hypotheses concern the role of the marital and parent-child relationships in mediating genetic influences on maternal adjustment and on the importance of the mothers' marital partners as a specifiable source of influences on their adjustment not shared with their sisters. The study's sample of 150 monozygotic (MZ) twins and 176 dizygotic (DZ) twins was drawn randomly from the Swedish Twin Registry and is, with some small exceptions, likely to be representative of women in the Swedish population. The sample included the marital partners of these twins and their adolescent children. Self-report and coded videotapes were a source of information about family process. Results reported in this first report focus on comparability of American and Swedish samples on scales measuring psychiatric symptoms, and on an analysis of genetic and environmental influences on nine measures of mothers' adjustment. Results suggest comparability between the US and Sweden. Genetic influences were found for all measures of adjustment, particularly in the psychological manifestations of anxiety and for smoking. The pattern of findings also underscored the importance of influences unique to each sibling within the twin pair, thus focusing attention on the potential role of marital partners in maternal adjustment. Results also suggested that experiences shared by the twin sisters, experiences unrelated to their genetic similarity, may influence their fearfulness and alcohol consumption. Our model did not include these influences and thus must be amended. [source] Developmental path between language and autistic-like impairments: a twin studyINFANT AND CHILD DEVELOPMENT, Issue 2 2008Katharina Dworzynski Abstract Autism spectrum disorders (ASDs) are diagnosed when individuals show impairments in three behavioural domains: communication, social interactions, and repetitive, restrictive behaviours and interests (RRBIs). Recent data suggest that these three sets of behaviours are genetically heterogeneous. Early language delay is strongly associated with ASD, but the basis for this association and the relationship with individual sub-domains of ASD has not been systematically investigated. In the present study, data came from a population-based twin sample with language development data at 2,4 years, measured by the MacArthur Communicative Development Inventory (MCDI), and data at 8 years using the Childhood Asperger Syndrome Test (CAST). For the total CAST and the three subscales at 8 years, approximately 300 same-sex twin pairs were selected as showing extreme autistic-like traits (ALTs), defined here as pairs in which at least one member of the twin pair scored in the highest 5% of the distribution. Phenotypic analyses indicated that children showing extreme social and communication ALTs (but not the RRBI subscale) at 8 years were below average in language development at 2,4 years. A regression model for selected twin data suggested that genetic influences account for this overlap, but that these effects are only in part mediated by genes that are shared between language and extreme autistic traits. Copyright © 2008 John Wiley & Sons, Ltd. [source] Monozygotic twins are discordant for chronic periodontitis: clinical and bacteriological findingsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2010Gaudy L. Torres de Heens Torres de Heens GL, Loos BG, van der Velden U. Monozygotic twins are discordant for chronic periodontitis: clinical and bacteriological findings. J Clin Periodontol 2010; 37: 120,128. doi: 10.1111/j.1600-051X.2009.01511.x. Abstract Objectives: The aim of this study was to assess, in monozygotic (MZ) and dizygotic (DZ) twin pairs in whom the proband of the twin pair was suffering from moderate to severe chronic periodontitis, the contribution of genetics, periodontal pathogens and lifestyle factors towards the clinical phenotype. Material and Methods: For this study, 18 adult twin pairs were selected on the basis of interproximal attachment loss (AL) 5 mm in 2 non-adjacent teeth in one twin member. The study included 10 MZ and eight DZ twin pairs, in whom the periodontal condition, presence of periodontal pathogens, educational level, smoking behaviour and body mass index (BMI) were evaluated. Results: Both MZ and DZ twins were discordant regarding AL and alveolar bone loss. Discordance was greater in DZ compared with MZ twins. In MZ twins, the discordance could not be explained by education, smoking, BMI and periodontal pathogens. In DZ twins, 45.6% of the discordance could be explained by more pack-years of the probands. Conclusion: The results confirm a possible role of genetic factors in periodontitis. However, the magnitude of the genetic effects on disease severity may have been overestimated previously. [source] Studies of twins: what can they tell us about the fetal origins of adult disease?PAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 2005Ruth Morley Summary There has been much interest in evidence that people with lower birthweight have higher risk of adult cardiovascular disease, but the causal pathways underlying such observations are uncertain. Study of twins offers an opportunity to shed light on the underlying causal pathways, in particular by investigating the role of ,shared' factors vs. factors affecting each individual fetus. This involves comparing results of within-cohort vs. within-pair analyses. Twins share many factors during gestation but birthweight discordance (difference in birthweight within a twin pair) cannot be determined by these shared factors and must relate to factors affecting growth of each individual fetus. If associations seen in a cohort of twins remain in within-pair analyses, then factors specific to each individual must be involved in the underlying causal pathways. Conversely, if the relationships disappear or substantially diminish in within-pair analyses, then factors common to the pair must be involved. Comparison of findings in monozygotic vs. dizygotic twins may provide insights into the role of genetic factors, although issues related to chorionicity need to be taken into account. We tabulate published data and conclude that differences in methodology and analyses preclude informative meta-analysis, and that analysis of pooled data would provide more useful information. [source] A study of the occurrence of monochorionic and monozygotic twinning in the pigANIMAL GENETICS, Issue 1 2009D. Bjerre Summary In humans as well as in most farm animals, monozygotic twins have been described. Nevertheless, only a few reports of twinning in the pig have been published. It has been suggested that monozygotic twins are formed during the first 14 days of pregnancy. This monozygotic twin study includes the investigation of porcine monochorionic embryos from 76 sows at days 26,29 post-insemination (p.i.), as well as an examination of 10 whole litters at days 21,22 p.i. In the former group, 29% of the sows carried monochorionic embryos. Based on DNA profiling using microsatellite markers, one monozygotic twin pair was found among these embryos. In the latter group, three monozygotic twin pairs were identified. Thus, it can be concluded that although the occurrence of monozygotic twins in pigs is a sporadic event, the fusion of extra-embryonic membranes is relatively common. [source] Selected neonatal outcomes in dizygotic twins after IVF versus non-IVF pregnanciesBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2010B Källén Please cite this paper as: Källén B, Finnström O, Lindam A, Nilsson E, Nygren K-G, Otterblad Olausson P. Selected neonatal outcomes in dizygotic twins after IVF versus non-IVF pregnancies. BJOG 2010; Objective, To compare neonatal outcome among twins conceived after in vitro fertilisation (IVF) with that of spontaneously conceived twins. Design, Comparison of different-sex (dizygotic) twins born after IVF with non-IVF dizygotic twins. Setting, National health registers in Sweden. Population, All births in Sweden during the period 1982,2007. Methods, We studied gestational duration, lowest birthweight and birthweight difference in the twin pair, presence of one or two twins with a respiratory complication, and with jaundice in one or both twins. Risk estimates were calculated as odds ratios with adjustments for year of birth, maternal age, parity and smoking in pregnancy. Main outcome measures, Gestational duration, birth weight, respiratory complications, jaundice. Results, We studied 1545 pairs of dizygotic twins born after IVF, and 8675 pairs of dizygotic twins where IVF was not known to have occurred. The risk for preterm delivery before 32 weeks of gestation was significantly increased among dizygotic twin pairs born after IVF compared with non-IVF dizygotic twin pairs. No significant difference in low birthweight or birthweight difference within twin pairs was seen. There was an increased occurrence of twin pairs with respiratory problems or jaundice, but only the latter diagnosis occurred in a statistically significant excess. Conclusions, The study confirms recent findings that IVF is associated with an increased risk for some neonatal complications, not only among singletons but also among twins. [source] Depression and obesity: do shared genes explain the relationship?DEPRESSION AND ANXIETY, Issue 9 2010Niloofar Afari Ph.D. Abstract Background: Studies have found a modest association between depression and obesity, especially in women. Given the substantial genetic contribution to both depression and obesity, we sought to determine whether shared genetic influences are responsible for the association between these two conditions. Methods: Data were obtained from 712 monozygotic and 281 dizygotic female twin pairs who are members of the community-based University of Washington Twin Registry. The presence of depression was determined by self-report of doctor-diagnosed depression. Obesity was defined as body mass index of ,30,kg/m2, based on self-reported height and weight. Generalized estimating regression models were used to assess the age-adjusted association between depression and obesity. Univariate and bivariate structural equation models estimated the components of variance attributable to genetic and environmental influences. Results: We found a modest phenotypic association between depression and obesity (odds ratio=1.6, 95% confidence interval=1.2,2.1). Additive genetic effects contributed substantially to depression (57%) and obesity (81%). The best-fitting bivariate model indicated that 12% of the genetic component of depression is shared with obesity. Conclusions: The association between depression and obesity in women may be in part due to shared genetic risk for both conditions. Future studies should examine the genetic, environmental, social, and cultural mechanisms underlying the relationship between this association. Depression and Anxiety, 2010. © 2010 Wiley-Liss, Inc. [source] Heritability of antisocial behaviour at 9: do callous-unemotional traits matter?DEVELOPMENTAL SCIENCE, Issue 1 2008Essi Viding A previous finding from our group indicated that teacher-rated antisocial behaviour (AB) among 7-year-olds is particularly heritable in the presence of callous-unemotional (CU) traits. Using a sample of 1865 same-sex twin pairs, we employed DeFries-Fulker extremes analysis to investigate whether teacher-rated AB with/without CU traits also shows aetiological differences among 9-year-olds. Furthermore, we assessed whether the differences in the magnitude of heritability would be evident even when hyperactive symptoms were controlled for in the statistical analysis. AB among 9-year-olds was more heritable with than without concomitant CU. The heritability difference was even more pronounced in magnitude when hyperactive symptoms were controlled. CU traits thus appear to index one valid way of sub-typing children with early-onset AB. [source] No clear genetic influences on the association between dyslexia and anxiety in a population-based sample of female twinsDYSLEXIA, Issue 4 2009Andrew J.O. Whitehouse Abstract Individuals with dyslexia are at an increased risk for anxiety disorders (e.g. generalized anxiety disorder, stress disorders, panic disorder). The extent to which this association is mediated by genetic and/or environmental influences is unclear. The current study explored the relationship between these two phenotypes using a large population-based twin sample. In total, 940 monozygotic and 903 dizygotic female twin pairs were included in the analyses. The presence of dyslexia and anxiety was determined by self-report of diagnosis by a health professional. Tetrachoric correlations confirmed an association between the two phenotypes, but suggested that there was no evidence for shared genetic risks. Bivariate twin modelling corroborated this finding and indicated the relationship between dyslexia and anxiety is mediated by shared environmental factors. Future research should seek to identifying the environmental factors that increase the vulnerability of individuals with dyslexia to emotional problems should be a priority for future research. Copyright © 2008 John Wiley & Sons, Ltd. [source] Gender ratios for reading difficultiesDYSLEXIA, Issue 3 2009Jesse L. Hawke Abstract The prevalence of reading difficulties is typically higher in males than females in both referred and research-identified samples, and the ratio of males to females is greater in more affected samples. To explore possible gender differences in reading performance, we analysed data from 1133 twin pairs in which at least one member of each pair had a school history of reading problems and from 684 twin pairs from a comparison sample with no reading difficulties. Although the difference between the average scores of males and females in these two samples was very small, the variance of reading performance was significantly greater for males in both groups. We suggest that a greater variance of reading performance measures in males may account at least in part for their higher prevalence of reading difficulties as well as for the higher gender ratios that are observed in more severely impaired samples. Copyright © 2009 John Wiley & Sons, Ltd. [source] Genetic influences on reading difficulties in boys and girls: the Colorado twin studyDYSLEXIA, Issue 1 2006Jesse L. Hawke Abstract To test the hypothesis that the genetic etiology for reading disability may differ in males and females, data from identical and fraternal twin pairs were analysed using both concordance and multiple regression methods. The sample included 264 identical (129 male, 135 female) and 214 same-sex fraternal (121 male, 93 female) twin pairs in which at least one member of each pair had reading difficulties. The difference between the identical and fraternal twin pair concordance rates was slightly larger for females than for males, suggesting a possible sex difference in etiology; however, a loglinear analysis of the three-way interaction of sex, zygosity, and concordance was not significant (p,0.17). The estimate of group heritability (hg2), a standardized measure of the extent to which reading difficulties are due to genetic influences, was somewhat greater for females than males (0.65 vs 0.54), but this difference was also not significant (p,0.35). Gender differences in hg2 were larger for younger children (less than 11.5 years of age) than for older children. However, the three-way interaction of sex, zygosity, and age was not significant when age was treated either categorically (p,0.86) or continuously (p,0.71). Thus, results of this study provide little or no evidence for a differential genetic etiology of reading difficulties in males and females. Copyright © 2005 John Wiley & Sons, Ltd. [source] Gender differences in genetic and environmental influences on gambling: results from a sample of twins from the National Longitudinal Study of Adolescent HealthADDICTION, Issue 3 2010Kevin M. Beaver ABSTRACT Aims To examine the extent to which genetic factors and shared and non-shared environmental factors are implicated in the development of gambling behaviors and to examine whether there are gender differences in the genetic and environmental contributors to gambling behaviors. Design A genetically informative analysis was performed by using DeFries,Fulker (DF) analysis. Setting Analysis of secondary data drawn from the National Longitudinal Study of Adolescent Health (Add Health). Participants A total of 324 monozygotic (MZ) twins and 278 same-sex dizygotic (DZ) twins were included in the analysis. Of these twins, there were 150 male MZ twins, 144 male DZ twins, 174 female MZ twins and 134 female DZ twins. Measurements Gambling behavior was measured through eight self-reported questions that tapped a range of items designed to measure problems related to gambling. Self-reported measures of self-control and delinquent involvement were also included to examine the degree to which these factors covaried with gambling behavior. Findings The results of the DF analysis indicated that when male and female twin pairs were analyzed simultaneously, genetic factors explained approximately 70% of the variance in gambling and non-shared environmental factors explained the remaining variance. When gender-specific models were calculated, substantial gender differences emerged. For males, genetic factors explained approximately 85% of the variance in gambling, with the non-shared environment accounting for the remaining variance. For females, genetic factors explained none of the variance in gambling behaviors, while the shared environment explained 45% of the variance and the non-shared environment explained 55% of the variance. Conclusions Analysis of twins from the Add Health data suggests that there are significant gender differences in the genetic and environmental underpinnings to gambling behaviors. [source] Physical activity in adolescence and smoking in young adulthood: a prospective twin cohort studyADDICTION, Issue 7 2007Urho M. Kujala ABSTRACT Aims To control for familial confounds, we studied the association between adolescent physical activity and later smoking in twin siblings discordant for their baseline physical activity. Design and measurements In this prospective population-based twin study, we asked whether persistent physical activity/inactivity in adolescence (assessed at 16, 17 and 18.5 years) predicted questionnaire-reported daily smoking at ages 22,27. Twins who, on the three baseline questionnaires, consistently reported frequent leisure physical activity (more than three times weekly) were classified as persistent exercisers, those who exercised less than three times monthly were called persistently inactive, others were occasional exercisers. Setting Finland. Participants A total of 4240 individuals, including 1870 twin pairs. Findings In analyses of individual twins, compared to persistent activity, persistent physical inactivity predicted increased risk of daily smoking (age- and sex-adjusted odds ratio 5.53, 95% confidence interval 3.88,7.88, P < 0.001). The risk remained elevated even after excluding all those who had smoked 50 cigarettes or more life-time at baseline and adjusted for educational level in adolescence. In within-pair analyses compared to the active members of discordant twin pairs, the physically inactive co-twins had increased risk of future daily smoking (sex-adjusted odds ratio 3.39, 95% confidence interval 1.56,7.39, P = 0.002). Conclusions Persistent physical inactivity in adolescence relates to adult smoking, even after familial factors are taken into account. [source] Gene expression analysis in absence epilepsy using a monozygotic twin designEPILEPSIA, Issue 9 2008Ingo Helbig Summary Purpose: To identify genes involved in idiopathic absence epilepsies by analyzing gene expression using a monozygotic (MZ) twin design. Methods: Genome-wide gene expression in lymphoblastoid cell lines (LCLs) was determined using microarrays derived from five discordant and four concordant MZ twin pairs with idiopathic absence epilepsies and five unaffected MZ twin pairs. Gene expression was analyzed using three strategies: discordant MZ twins were compared as matched pairs, MZ twins concordant for epilepsy were compared to control MZ twins, and a singleton design of affected versus unaffected MZ twin individuals was used irrespective of twin pairing. An overlapping gene list was generated from these analyses. Dysregulation of genes recognized from the microarray experiment was validated using quantitative real time PCR (qRT-PCR) in the twin sample and in an independent sample of 18 sporadic absence cases and 24 healthy controls. Results: Sixty-five probe sets were identified from the three combined microarray analysis strategies. Sixteen genes were chosen for validation and nine of these genes confirmed by qRT-PCR in the twin sample. Differential expression for EGR1 (an immediate early gene) and RCN2 (coding for the calcium-binding protein Reticulocalbin 2) were reconfirmed by qRT-PCR in the independent sample. Discussion: Using a unique sample of discordant MZ twins, our study identified genes with altered expression, which suggests novel mechanisms in idiopathic absence epilepsy. Dysregulation of EGR1 and RCN2 is implicated in idiopathic absence epilepsy. [source] The genetics of tea and coffee drinking and preference for source of caffeine in a large community sample of Australian twinsADDICTION, Issue 10 2005Michelle Luciano ABSTRACT Aims To investigate the genetic and environmental influences on tea consumption and their commonalities with coffee consumption; and to further examine the genetic and environmental aetiology of preference for tea/coffee. Design A classical twin design was used in which the similarity of identical and non-identical twins is compared, enabling estimates of genetic, common environmental and unique environmental influence on the trait. Setting and participants An Australian population-based sample of 1796 identical (i.e. monozygotic) and 2013 non-identical (i.e. dizygotic) twin pairs aged 16,87 years was studied, roughly three-fifths of whom were female. The sample represented approximately 70% of those approached for study participation. Measurements As part of a Health and Lifestyle Questionnaire, respondents were asked how many cups of each tea and coffee they consumed per day. Additional measures of ,total tea and coffee consumption' and ,preference for coffee' were calculated. Findings Age was positively associated with tea consumption but negatively associated with coffee preference; women consumed more beverages than men, but showed a lower preference for coffee. An inverse relation between tea and coffee consumption,larger in females (,0.41) than males (,0.34),was supported. This association was mediated entirely by the unique environment in males, and by both the unique environment (68.3%) and genes (31.7%) in females. Tea and coffee drinking were shown to have similar heritabilities (0.46) in males, but tea consumption was influenced by common environmental factors whereas coffee consumption was not. Coffee preference was shown to be influenced by genes (0.42) and the unique environment (0.58). Conclusions As the patterns of genetic and environmental variation were shown to differ for tea and coffee consumption it may be more informative to retain them as separate measures of caffeine intake in future studies of stimulant use and taste perception. [source] Analysis of genetic influences on the consistency and variability of the Big Five across different stressful situationsEUROPEAN JOURNAL OF PERSONALITY, Issue 5 2001Gerty Lensvelt-Mulders Several studies have demonstrated that individual differences in personality traits, known as the Big Five, have a genetic component. These personality traits are considered important predictors of everyday behaviour. In addition to personality traits there are also factors in the environment that govern behaviour. This dual influence on behaviour is statistically reflected in a P,×,S interaction. This study examines the genetic and environmental influences on the interactions between a person and his daily life environment for the Big Five. Fifty-seven identical twin pairs and 43 fraternal twin pairs participated in this study. Trait related behaviour was measured in 30 different situations with the aid of an SR inventory. The heritability coefficients for the main effect of P were in the normal range, varying between 0.35 for Agreeableness and 0.53 for Conscientiousness. The heritability coefficients for the P,×,S interactions were moderately high, explaining between 26% and 69% of the total P,×,S variance. The consequences of these results for general and behavioural genetic research on the Big Five will be discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Genetic and environmental influences on Anxious/Depression during childhood: a study from the Netherlands Twin RegisterGENES, BRAIN AND BEHAVIOR, Issue 8 2005D. I. Boomsma For a large sample of twin pairs from the Netherlands Twins Register who were recruited at birth and followed through childhood, we obtained parental ratings of Anxious/Depression (A/D). Maternal ratings were obtained at ages 3 years (for 9025 twin pairs), 5 years (9222 pairs), 7 years (7331 pairs), 10 years (4430 pairs) and 12 years (2363 pairs). For 60,90% of the pairs, father ratings were also available. Multivariate genetic models were used to test for rater-independent and rater-specific assessments of A/D and to determine the genetic and environmental influences on individual differences in A/D at different ages. At all ages, monozygotic twins resembled each other more closely for A/D than dizygotic twins, implying genetic influences on variation in A/D. Opposite sex twin pairs resembled each other to same extent as same-sex dizygotic twins, suggesting that the same genes are expressed in boys and girls. Heritability estimates for rater-independent A/D were high in 3-year olds (76%) and decreased in size as children grew up [60% at age 5, 67% at age 7, 53% at age 10 (60% in boys) and 48% at age 12 years]. The decrease in genetic influences was accompanied by an increase in the influence of the shared family environment [absent at ages 3 and 7, 16% at age 5, 20% at age 10 (5% in boys) and 18% at age 12 years]. The agreement between parental A/D ratings was between 0.5 and 0.7, with somewhat higher correlations for the youngest group. Disagreement in ratings between the parents was not merely the result of unreliability or rater bias. Both the parents provided unique information from their own perspective on the behavior of their children. Significant influences of genetic and shared environmental factors were found for the unique parental views. At all ages, the contribution of shared environmental factors to variation in rater-specific views was higher for father ratings. Also, at all ages except age 12, the heritability estimates for the rater-specific phenotype were higher for mother ratings (59% at age 3 and decreasing to 27% at age 12 years) than for father ratings (between 14 and 29%). Differences between children, even as young as 3 years, in A/D are to a large extent due to genetic differences. As children grow up, the variation in A/D is due in equal parts to genetic and environmental influences. Anxious/Depression, unlike many other common childhood psychopathologies, is influenced by the shared family environment. These findings may provide support for why certain family therapeutic approaches are effective in the A/D spectrum of illnesses. [source] Common genetic influences underlie comorbidity of migraine and endometriosisGENETIC EPIDEMIOLOGY, Issue 2 2009Dale R. Nyholt Abstract We examined the co-occurrence of migraine and endometriosis within the largest known collection of families containing multiple women with surgically confirmed endometriosis and in an independent sample of 815 monozygotic and 457 dizygotic female twin pairs. Within the endometriosis families, a significantly increased risk of migrainous headache was observed in women with endometriosis compared to women without endometriosis (odds ratio [OR] 1.57, 95% confidence interval [CI]: 1.12,2.21, P=0.009). Bivariate heritability analyses indicated no evidence for common environmental factors influencing either migraine or endometriosis but significant genetic components for both traits, with heritability estimates of 69 and 49%, respectively. Importantly, a significant additive genetic correlation (rG = 0.27, 95% CI: 0.06,0.47) and bivariate heritability (h2=0.17, 95% CI: 0.08,0.27) was observed between migraine and endometriosis. Controlling for the personality trait neuroticism made little impact on this association. These results confirm the previously reported comorbidity between migraine and endometriosis and indicate common genetic influences completely explain their co-occurrence within individuals. Given pharmacological treatments for endometriosis typically target hormonal pathways and a number of findings provide support for a relationship between hormonal variations and migraine, hormone-related genes and pathways are highly plausible candidates for both migraine and endometriosis. Therefore, taking into account the status of both migraine and endometriosis may provide a novel opportunity to identify the genes underlying them. Finally, we propose that the analysis of such genetically correlated comorbid traits can increase power to detect genetic risk loci through the use of more specific, homogenous and heritable phenotypes. Genet. Epidemiol. 2008. © 2008 Wiley-Liss, Inc. [source] Heritability of regional and global brain structure at the onset of puberty: A magnetic resonance imaging study in 9-year-old twin pairsHUMAN BRAIN MAPPING, Issue 7 2009Jiska S. Peper Abstract Puberty represents the phase of sexual maturity, signaling the change from childhood into adulthood. During childhood and adolescence, prominent changes take place in the brain. Recently, variation in frontal, temporal, and parietal areas was found to be under varying genetic control between 5 and 19 years of age. However, at the onset of puberty, the extent to which variation in brain structures is influenced by genetic factors (heritability) is not known. Moreover, whether a direct link between human pubertal development and brain structure exists has not been studied. Here, we studied the heritability of brain structures at 9 years of age in 107 monozygotic and dizygotic twin pairs (N = 210 individuals) using volumetric MRI and voxel-based morphometry. Children showing the first signs of secondary sexual characteristics (N = 47 individuals) were compared with children without these signs, based on Tanner-stages. High heritabilities of intracranial, total brain, cerebellum, and gray and white matter volumes (up to 91%) were found. Regionally, the posterior fronto-occipital, corpus callosum, and superior longitudinal fascicles (up to 93%), and the amygdala, superior frontal and middle temporal cortices (up to 83%) were significantly heritable. The onset of secondary sexual characteristics of puberty was associated with decreased frontal and parietal gray matter densities. Thus, in 9-year-old children, global brain volumes, white matter density in fronto-occipital and superior longitudinal fascicles, and gray matter density of (pre-)frontal and temporal areas are highly heritable. Pubertal development may be directly involved in the decreases in gray matter areas that accompany the transition of our brains from childhood into adulthood. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Developmental path between language and autistic-like impairments: a twin studyINFANT AND CHILD DEVELOPMENT, Issue 2 2008Katharina Dworzynski Abstract Autism spectrum disorders (ASDs) are diagnosed when individuals show impairments in three behavioural domains: communication, social interactions, and repetitive, restrictive behaviours and interests (RRBIs). Recent data suggest that these three sets of behaviours are genetically heterogeneous. Early language delay is strongly associated with ASD, but the basis for this association and the relationship with individual sub-domains of ASD has not been systematically investigated. In the present study, data came from a population-based twin sample with language development data at 2,4 years, measured by the MacArthur Communicative Development Inventory (MCDI), and data at 8 years using the Childhood Asperger Syndrome Test (CAST). For the total CAST and the three subscales at 8 years, approximately 300 same-sex twin pairs were selected as showing extreme autistic-like traits (ALTs), defined here as pairs in which at least one member of the twin pair scored in the highest 5% of the distribution. Phenotypic analyses indicated that children showing extreme social and communication ALTs (but not the RRBI subscale) at 8 years were below average in language development at 2,4 years. A regression model for selected twin data suggested that genetic influences account for this overlap, but that these effects are only in part mediated by genes that are shared between language and extreme autistic traits. Copyright © 2008 John Wiley & Sons, Ltd. [source] Infant visual habituation and parental psychological distressINFANT MENTAL HEALTH JOURNAL, Issue 4 2001David P. Laplante Research is equivocal concerning the relationship between parental psychological distress and infant cognitive functioning. Four potential limitations of the literature are addressed: reliance on mothers' but not fathers' psychological distress, use of categorical measures of psychological distress, use of standardized measures of infant cognitive functioning, and failure to take into account potential gender differences. Ninety-nine twin pairs and both their mothers and fathers were assessed. Infants cognitive functioning was assessed using an infant-controlled habituation,recovery,dishabituation task. Maternal and paternal psychological distress was assessed using the Symptom Check List-90-Revised. No gender differences were obtained for infant visual information-processing abilities or parental psychological distress. Maternal and paternal psychological distress was related to female visual encoding abilities only. It was concluded that parental psychological distress might degrade parent,infant interactions. Characteristics of girls when faced with parents exhibiting psychiatric difficulties may exacerbate difficulties of parent,infant interactions, thereby hindering the full development of cognitive abilities involved in the process of habituation. A need exists to examine the relationship between parental psychological distress and infant visual attention separately for girls and boys. ©2001 Michigan Association for Infant Mental Health. [source] Environmental factors in inflammatory bowel disease: A co-twin control study of a Swedish-Danish twin populationINFLAMMATORY BOWEL DISEASES, Issue 10 2006Jonas Halfvarson MD Abstract Background: Genetics and environmental factors are implicated in the etiology of inflammatory bowel disease (IBD). We studied environmental factors in a population-based Swedish-Danish twin cohort using the co-twin control method. Subjects and Methods: A questionnaire was sent to 317 twin pairs regarding markers of exposures in the following areas: infections/colonization and diet as well as smoking, appendectomy, and oral contraceptives. Odds ratios (OR) were calculated by conditional logistic regression. When confounding appeared plausible, multivariate conditional logistic regression was added. The questions were also divided into topic groups, and adjustment was made for multiple testing within each of the groups. Results: The response rate to the questionnaire was 83%. In consideration of the study design, only discordant pairs were included (Crohn's disease [CD], n = 102; ulcerative colitis [UC], n > = 125). Recurrent gastrointestinal infections were associated with both UC (OR, 8.0; 95% confidence interval [CI], 1.0,64) and CD (OR, 5.5; 95% CI, 1.2,25). Hospitalization for gastrointestinal infections was associated with CD (OR, 12; 95% CI, 1.6,92). Smoking was inversely associated with UC (OR, 0.4; 95% CI, 0.2,0.9) and associated with CD (OR, 2.9; 95% CI, 1.2,7.1). Conclusions: The observed associations indicate that markers of possible infectious events may influence the risk of IBD. Some of these effects might be mediated by long-term changes in gut flora or alterations in reactivity to the flora. The influence of smoking in IBD was confirmed. [source] Investigation of quality of the parental relationship as a risk factor for subclinical bulimia nervosaINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 4 2001Tracey D. Wade Abstract Objective Previous literature suggests a link between the quality of the parental relationship and disordered eating in offspring. We investigated the relationship between offspring pyschopathology and the parental relationship using a population-based twin registry that contained 766 complete twin pairs. Method We used reports of twin lifetime psychopathology from the twins and quality of parental relationship and parental lifetime psychopathology from both parents. Results Poorer quality of the marital relationship predicted the presence of subclinical bulimia nervosa (SBN) using both mother's (odds ratio [OR] = 0.83, 95% confidence interval [CI]: 0.71,0.97) and father's (OR = 0.78, 95% CI: 0.62,0.97) reports. It also predicted the presence of generalized anxiety disorder (GAD) and alcohol dependence. SBN was still strongly predicted by the marital relationship when parental psychopathology was included as a covariate. Discussion These results are supportive of the notion that a conflictual and distant marital relationship can, at least partially, act as an environmental risk factor for SBN. © 2001 by John Wiley & Sons, Inc. Int J Eat Disord 30: 389,400, 2001. [source] Long-Term Leisure Time Physical Activity and Properties of Bone: A Twin Study,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2009Hongqiang Ma Abstract Effects of physical activity on bone properties, when controlled for genetic effects, are not fully understood. We aimed to study the association between long-term leisure time physical activity (LTPA) and bone properties using twin pairs known to be discordant for leisure time physical activity for at least 30 yr. Volumetric BMD and geometric properties were measured at the tibia shaft and distal end using pQCT in 16 middle-aged (50,74 yr) same-sex twin pairs (seven monozygotic [MZ] and nine dizygotic [DZ] pairs) selected from a population-based cohort. Paired differences between active and inactive co-twins were studied. Active members of MZ twin pairs had larger cortical bone cross-sectional area (intrapair difference: 8%, p = 0.006), thicker cortex (12%, p = 0.003), and greater moment of inertia (Imax, 20%, p = 0.024) at the tibia shaft than their inactive co-twins. At the distal tibia, trabecular BMD (12%, p = 0.050) and compressive strength index (18%, p = 0.038) were also higher in physically active MZ pair members than their inactive co-twins. The trends were similar, but less consistently so, in DZ pairs as in MZ pairs. Our genetically controlled study design shows that LTPA during adulthood strengthens bones in a site-specific manner, that is, the long bone shaft has a thicker cortex, and thus higher bending strength, whereas the distal bone has higher trabecular density and compressive strength. These results suggest that LTPA has a potential causal role in decreasing the long-term risk of osteoporosis and thus preventing osteoporotic fractures. [source] Genetic Contribution to Bone Metabolism, Calcium Excretion, and Vitamin D and Parathyroid Hormone RegulationJOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2001D. Hunter Abstract A classical twin study was performed to assess the relative contribution of genetic and environmental factors to bone metabolism, calcium homeostasis, and the hormones regulating them. It was examined further whether the genetic effect is menopause dependent. The subjects were 2136 adult twins (98.3% female): 384 monozygotic (MZ) and 684 dizygotic (DZ) twin pairs. The intraclass correlations were calculated, and maximum likelihood model fitting was used to estimate genetic and environmental variance components. The intraclass correlations for all of the variables assessed were higher in MZ twin pairs. The heritabilities (95% CIs) obtained from model fitting for hormones regulating bone metabolism and calcium homeostasis were parathyroid hormone (PTH), 60% (54,65%); 25-hydroxyvitamin D [25(OH)D]; 43% (28,57%), 1,25-hydroxyvitamin D [1,25(OH)], 65% (53,74%); and vitamin D binding protein 62% (56,66%). The heritabilities (95% CIs) for markers of bone formation also were assessed; bone-specific alkaline phosphatase (BSAP), 74% (67,80%), and osteocalcin, 29% (14,44%); marker of bone resorption deoxypyridinoline (DPD), 58% (52,64%); and measure of calcium homeostasis 24 h urine calcium, creatinine (Cr), 52% (41,61%). The magnitude of genetic influence differed with menopause for most variables. This study provides evidence for the importance of genetic factors in determining bone resorption and formation, calcium excretion, and the hormones regulating these processes. It shows for the first time a clear genetic effect on bone resorption in premenopausal women and the regulation of PTH, vitamin D metabolism, and calcium excretion. The genes controlling bone hormones and markers are likely to be useful therapeutic and diagnostic targets. [source] Monozygotic twins are discordant for chronic periodontitis: clinical and bacteriological findingsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 2 2010Gaudy L. Torres de Heens Torres de Heens GL, Loos BG, van der Velden U. Monozygotic twins are discordant for chronic periodontitis: clinical and bacteriological findings. J Clin Periodontol 2010; 37: 120,128. doi: 10.1111/j.1600-051X.2009.01511.x. Abstract Objectives: The aim of this study was to assess, in monozygotic (MZ) and dizygotic (DZ) twin pairs in whom the proband of the twin pair was suffering from moderate to severe chronic periodontitis, the contribution of genetics, periodontal pathogens and lifestyle factors towards the clinical phenotype. Material and Methods: For this study, 18 adult twin pairs were selected on the basis of interproximal attachment loss (AL) 5 mm in 2 non-adjacent teeth in one twin member. The study included 10 MZ and eight DZ twin pairs, in whom the periodontal condition, presence of periodontal pathogens, educational level, smoking behaviour and body mass index (BMI) were evaluated. Results: Both MZ and DZ twins were discordant regarding AL and alveolar bone loss. Discordance was greater in DZ compared with MZ twins. In MZ twins, the discordance could not be explained by education, smoking, BMI and periodontal pathogens. In DZ twins, 45.6% of the discordance could be explained by more pack-years of the probands. Conclusion: The results confirm a possible role of genetic factors in periodontitis. However, the magnitude of the genetic effects on disease severity may have been overestimated previously. [source] Genetic and environmental sources of continuity and change in teacher-rated aggression during early adolescenceAGGRESSIVE BEHAVIOR, Issue 4 2006Elina Vierikko Abstract Genetic and environmental sources of continuity and change in aggression were studied in a sample of 1,041 twin pairs (364 monozygotic; 348 same-sex dizygotic; and 329 opposite-sex dizygotic) as part of an ongoing, population-based Finnish twin-family study. At ages 12 and 14, the twins' aggression was assessed by their classroom teachers, using a rating form of the Multidimensional Peer Nomination Inventory. Genetic and environmental sources of continuity and change were studied by fitting a longitudinal bivariate Cholesky decomposition model. Longitudinal model-fitting results indicated that both genetic and environmental factors influenced continuity in aggression during this 2-year period, but the age-to-age correlation of these factors differed by sex. Continuity in boys' aggression was mediated by genes and common environmental factors; in girls, in contrast, continuity was due primarily to common environmental, and to a lesser degree, unique environmental factors. Genes and unique environments contributed to change in aggression in both sexes. Aggr. Behav. 31:1,13, 2006. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||||||||