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Nicotine & Tobacco Research : Official... Jun 2018Classical twin studies show that smoking is heritable. To determine if shared family environment plays a role in addition to genetic factors, and if they interact...
INTRODUCTION
Classical twin studies show that smoking is heritable. To determine if shared family environment plays a role in addition to genetic factors, and if they interact (G×E), we use a children-of-twins design. In a second sample, we measure genetic influence with polygenic risk scores (PRS) and environmental influence with a question on exposure to smoking during childhood.
METHODS
Data on smoking initiation were available for 723 children of 712 twins from the Netherlands Twin Register (64.9% female, median birth year 1985). Children were grouped in ascending order of risk, based on smoking status and zygosity of their twin-parent and his/her co-twin: never smoking twin-parent with a never smoking co-twin; never smoking twin-parent with a smoking dizygotic co-twin; never smoking twin-parent with a smoking monozygotic co-twin; and smoking twin-parent with a smoking or never smoking co-twin. For 4072 participants from the Netherlands Twin Register (67.3% female, median birth year 1973), PRS for smoking were computed and smoking initiation, smoking heaviness, and exposure to smoking during childhood were available.
RESULTS
Patterns of smoking initiation in the four group children-of-twins design suggested shared familial influences in addition to genetic factors. PRS for ever smoking were associated with smoking initiation in all individuals. PRS for smoking heaviness were associated with smoking heaviness in individuals exposed to smoking during childhood, but not in non-exposed individuals.
CONCLUSIONS
Shared family environment influences smoking, over and above genetic factors. Genetic risk of smoking heaviness was only important for individuals exposed to smoking during childhood, versus those not exposed (G×E).
IMPLICATIONS
This study adds to the very few existing children-of-twins (CoT) studies on smoking and combines a CoT design with a second research design that utilizes polygenic risk scores and data on exposure to smoking during childhood. The results show that shared family environment affects smoking behavior over and above genetic factors. There was also evidence for gene-environment interaction (G×E) such that genetic risk of heavy versus light smoking was only important for individuals who were also exposed to (second-hand) smoking during childhood. Together, these findings give additional incentive to recommending parents not to expose their children to cigarette smoking.
Topics: Adolescent; Adult; Child; Cohort Studies; Female; Gene-Environment Interaction; Humans; Male; Netherlands; Parents; Registries; Risk Factors; Smoking; Surveys and Questionnaires; Twins, Dizygotic; Twins, Monozygotic
PubMed: 28575460
DOI: 10.1093/ntr/ntx121 -
Genes, Brain, and Behavior Jun 2006Since each individual produced by the sexual process contains a unique set of genes, very exceptional combinations of genes are unlikely to appear twice even within the... (Review)
Review
Since each individual produced by the sexual process contains a unique set of genes, very exceptional combinations of genes are unlikely to appear twice even within the same family. E. O. Wilson (1978)The intraclass correlations of monozygotic twins who were separated in infancy and reared apart (MZA twins) provide estimates of trait heritability, and the Minnesota Study of Twins Reared Apart [MISTRA: Bouchard et al. (1990), The sources of human psychological differences: the Minnesota study of twins reared apart, Science 250, 223-228] has demonstrated that MZA pairs are as similar in most respects as MZ pairs reared together. Some polygenic traits--e.g. stature, IQ, harm avoidance, negative emotionality, interest in sports--are polygenic-additive, so pairs of relatives resemble one another on the given trait in proportion to their genetic similarity. But the existence and the intensity of other important psychological traits seem to be emergent properties of gene configurations (or configurations of independent and partially genetic traits) that interact multiplicatively rather than additively. Monozygotic (MZ) twins may be strongly correlated on such emergenic traits, while the similarity of dizygotic (DZ) twins, sibs or parent-offspring pairs may be much less than half that of MZ pairs. Some emergenic traits, although strongly genetic, do not appear to run in families. MISTRA has provided at least two examples of traits for which MZA twins are strongly correlated, and DZA pairs correlate near zero, while DZ pairs reared together (DZTs) are about half as similar as MZTs. These findings suggest that even more traits may be emergenic than those already identified. Studies of adoptees reared together (who are perhaps more common than twins reared apart) may help to identify traits that are emergenic, but that also are influenced by a common rearing environment.
Topics: Adolescent; Child; Child Rearing; Child, Preschool; Gene Expression Regulation; Genetic Determinism; Genetic Variation; Humans; Pedigree; Personality; Phenotype; Polymorphism, Genetic; Quantitative Trait, Heritable; Social Environment; Twin Studies as Topic; Twins, Dizygotic; Twins, Monozygotic
PubMed: 16716200
DOI: 10.1111/j.1601-183X.2006.00233.x -
Behavior Genetics Mar 2017We compared the nature of the sibling relationship in dyads of varying genetic relatedness, employing a behavioural genetic design to estimate the contribution that...
We compared the nature of the sibling relationship in dyads of varying genetic relatedness, employing a behavioural genetic design to estimate the contribution that genes and the environment have on this familial bond. Two samples were used-the Sisters and Brothers Study consisted of 173 families with two target non-twin children (mean ages = 7.42 and 5.22 years respectively); and the Twins, Family and Behaviour study included 234 families with two target twin children (mean age = 4.70 years). Mothers and fathers reported on their children's relationship with each other, via a postal questionnaire (the Sisters and Brothers Study) or a telephone interview (the Twins, Family and Behaviour study). Contrary to expectations, no mean level differences emerged when monozygotic twin pairs, dizygotic twin pairs, and non-twin pairs were compared on their sibling relationship quality. Behavioural genetic analyses also revealed that the sibling bond was modestly to moderately influenced by the genetic propensities of the children within the dyad, and moderately to substantially influenced by the shared environment common to both siblings. In addition, for sibling negativity, we found evidence of twin-specific environmental influence-dizygotic twins showed more reciprocity than did non-twins. Our findings have repercussions for the broader application of results from future twin-based investigations.
Topics: Adult; Child; Child, Preschool; Environment; Fathers; Female; Genetics, Behavioral; Humans; Male; Mothers; Siblings; Social Behavior; Social Environment; Surveys and Questionnaires; Twins; Twins, Dizygotic; Twins, Monozygotic
PubMed: 27796609
DOI: 10.1007/s10519-016-9825-z -
Behaviour Research and Therapy Jul 1993Is optimism heritable? We gave the Attributional Style Questionnaire (ASQ), a measure of optimism, to 115 monozygotic twin pairs (MZ) and 27 dizygotic twin pairs (DZ).... (Comparative Study)
Comparative Study Review
Is optimism heritable? We gave the Attributional Style Questionnaire (ASQ), a measure of optimism, to 115 monozygotic twin pairs (MZ) and 27 dizygotic twin pairs (DZ). The intraclass correlations of the ASQ scores were 0.48 for MZ twins (P < 0.0001) and 0 for DZ twins. Though the sample size of DZ twins is small, these results suggest that there may be a substantial genetic effect on optimism. We speculate, however, that the mechanism for the transmission of this, and other complex personality traits, may be highly indirect.
Topics: Cognition; Emotions; Environment; Female; Humans; Male; Twins, Dizygotic; Twins, Monozygotic; Verbal Behavior
PubMed: 8347115
DOI: 10.1016/0005-7967(93)90108-7 -
JAMA Network Open Aug 2022Although infancy is the most rapid period of postnatal growth and development, factors associated with variation in infant traits are not well understood. (Meta-Analysis)
Meta-Analysis
IMPORTANCE
Although infancy is the most rapid period of postnatal growth and development, factors associated with variation in infant traits are not well understood.
OBJECTIVE
To synthesize the large twin study literature partitioning phenotypic variance in psychological traits and developmental milestones in infancy into estimates of heritability and shared and nonshared environment.
DATA SOURCES
PubMed, PsycINFO, and references of included publications were searched up to February 11, 2021.
STUDY SELECTION
Peer-reviewed publications using the classical twin design to study psychological traits and developmental milestones from birth to 2 years old were included.
DATA EXTRACTION AND SYNTHESIS
Data were extracted in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses and categorized using the International Classification of Functioning, Disability and Health: Children and Youth Version. Data were pooled in 3-level random effects models, incorporating within-cohort variance in outcome measurement and between-cohort variance. Data were analyzed from March 2021 through September 2021.
MAIN OUTCOMES AND MEASURES
The primary outcomes were monozygotic and dizygotic twin correlations. These were used to calculate genetic and shared and nonshared environment estimates.
RESULTS
Among 139 publications that were systematically retrieved, data were available on 79 044 twin pairs (31 053 monozygotic and 47 991 dizygotic pairs), 52 independent samples, and 21 countries. Meta-analyses were conducted on psychological traits and developmental milestones from 106 publications organized into 10 categories of functioning, disability, and health. Moderate to high genetic estimates for 8 categories were found, the highest of which was psychomotor functions (pooled h2, 0.59; 95% CI, 0.25-0.79; P < .001). Several categories of traits had substantial shared environment estimates, the highest being mental functions of language (pooled c2, 0.59; 95% CI, 0.24-0.86; P = .001). All examined categories of traits had moderate or high nonshared environment estimates, the highest of which were emotional functions (pooled e2, 0.42; 95% CI, 0.33-0.50; P < .001) and family relationships (pooled e2, 0.42; 95% CI, 0.30-0.55; P < .001).
CONCLUSIONS AND RELEVANCE
These findings may be an important source of information to guide future gene discovery research, public perspectives on nature and nurture, and clinical insights into the degree to which family history and environments may estimate major domains of infant functioning, disability, and health in psychological traits and developmental milestones.
Topics: Adolescent; Child; Cohort Studies; Forecasting; Humans; Infant; Phenotype; Twins, Dizygotic
PubMed: 35994288
DOI: 10.1001/jamanetworkopen.2022.27887 -
Genes, Brain, and Behavior Apr 2021Twin studies of insomnia exhibit heterogeneity in estimates of heritability. This heterogeneity is likely because of sex differences, age of the sample, the reporter and... (Meta-Analysis)
Meta-Analysis
Twin studies of insomnia exhibit heterogeneity in estimates of heritability. This heterogeneity is likely because of sex differences, age of the sample, the reporter and the definition of insomnia. The aim of the present study was to systematically search the literature for twin studies investigating insomnia disorder and insomnia symptoms and to meta-analyse the estimates of heritability derived from these studies to generate an overall estimate of heritability. We further examined whether heritability was moderated by sex, age, reporter and insomnia symptom. A systematic literature search of five online databases was completed on 24 January 2020. Two authors independently screened 5644 abstracts, and 160 complete papers for the inclusion criteria of twin studies from the general population reporting heritability statistics on insomnia or insomnia symptoms, written in English, reporting data from independent studies. We ultimately included 12 papers in the meta-analysis. The meta-analysis focussed on twin intra-class correlations for monozygotic and dizygotic twins. Based on these intra-class correlations, the meta-analytic estimate of heritability was estimated at 40%. Moderator analyses showed stronger heritability in females than males; and for parent-reported insomnia symptoms compared with self-reported insomnia symptoms. There were no other significant moderator effects, although this is likely because of the small number of studies that were comparable across levels of the moderators. Our meta-analysis provides a robust estimate of the heritability of insomnia, which can inform future research aiming to uncover molecular genetic factors involved in insomnia vulnerability.
Topics: Adult; Age Factors; Female; Humans; Male; Self Report; Sex Characteristics; Sleep Initiation and Maintenance Disorders; Twins, Dizygotic; Twins, Monozygotic
PubMed: 33222383
DOI: 10.1111/gbb.12717 -
Prenatal Diagnosis Sep 2022Prenatal chorionicity assessment relies on ultrasound, which can be confounded by many factors. Noninvasive assessment of zygosity is possible using single nucleotide...
OBJECTIVE
Prenatal chorionicity assessment relies on ultrasound, which can be confounded by many factors. Noninvasive assessment of zygosity is possible using single nucleotide polymorphism (SNP)-based cell-free DNA testing. Our objective was to determine the relationship between provider-reported chorionicity and SNP-cfDNA assignment of twin zygosity.
METHODS
All twin pregnancy blood samples received by a reference laboratory between September 27, 2017 and September 8, 2021 were included. Chorionicity assignment was requested on the requisition, recorded as; monochorionic (MC), dichorionic, or "don't know". SNP-cfDNA zygosity results, monozygotic (MZ) or dizygotic (DZ), were correlated with chorionicity assignment.
RESULTS
59,471 twin samples (median gestational age = 12.0 weeks at draw) were received and analyzed; 55,344 (93.1%) received zygosity assignment. SNP-cfDNA reported 16,673 (30.1%) MZ and 38,671 (69.9%) as DZ. Provider-reported chorionicity was compared to the zygosity assignment for each case. Of 6283 provider-reported MC twins, 318 (5.1%) were reported as DZ using SNP-cfDNA.
CONCLUSION(S)
One in 20 suspected MC twin pregnancies were reported as DZ using SNP-cfDNA. Approximately 30% of 55,344 twin pregnancies were found to be MZ, including cases where chorionicity was unknown. SNP-cfDNA zygosity assessment is a useful adjunct assessment for twin pregnancies, particularly those reported as MC or without determined chorionicity.
Topics: Female; Humans; Infant; Pregnancy; Cell-Free Nucleic Acids; Chorion; Polymorphism, Single Nucleotide; Pregnancy, Twin; Twins, Dizygotic; Twins, Monozygotic
PubMed: 35997139
DOI: 10.1002/pd.6218 -
BMC Pediatrics Feb 2023National Persian school-aged twin registry was established to provide a platform for twin studies. In this report, we describe defining registry characteristics,...
BACKGROUND
National Persian school-aged twin registry was established to provide a platform for twin studies. In this report, we describe defining registry characteristics, database design, and preliminary results regarding gathered data in the first phase of the registry program.
METHOD
Through focus group discussions, the required data elements to design the database and data collection process were defined. First, a list of twins in school-aged groups was retrieved from the electronic database of the Ministry of Education. Tehran schools were selected for the first phase of our registry. Standard "Pea-in-Pods" questionnaire and twins' similarity questionnaires were filled out by the parents themselves in addition to demographic information. Data were analyzed using SPSS v.22.
RESULTS
The first national school-aged twin registry was established in 2018. Firstly, the required data sets and data collection process were defined using focus group discussions. At the country level, the initial information on 189,738 students was retrieved from the national database of the Ministry of Education. They were born between 2003 and 2017, of which 94,997 are boys (50.1%) and 94,741 are girls (49.9%). Of them, a total of 5,642 pairs of school-aged twins participated in the first phase of our program. Our sample size comprised 9772 twins, 906 triples, and 92 quadruplets. The analysis of the zygosity questionnaire showed that 14% of twin pairs were identified as monozygotic twins.
CONCLUSION
Recruiting school-aged twins through school health assistants leads to high enrollment and decreasing costs for the twin registry. The study showed a high rate of dizygotic twins that need to be verified by twin bio-sample in the next phase of studies.
Topics: Male; Female; Humans; Child; Iran; Twins, Monozygotic; Twins, Dizygotic; Registries; Surveys and Questionnaires
PubMed: 36765320
DOI: 10.1186/s12887-023-03865-x -
Journal of the American Academy of... Feb 2019Psychotic experiences (PE) are dimensional phenomena in the general population that resemble psychotic symptoms, such as paranoia and hallucinations. This is the first...
OBJECTIVE
Psychotic experiences (PE) are dimensional phenomena in the general population that resemble psychotic symptoms, such as paranoia and hallucinations. This is the first twin study to explore the degree to which tobacco use and PE share genetic or environmental influences. Previous studies on the association between adolescent tobacco use and PE have not considered PE dimensionally, included negative symptoms, or accounted for confounding by sleep disturbance and stressful life events.
METHOD
An unselected adolescent twin sample (N = 3,787 pairs; mean age = 16.16 years) reported on PE (paranoia, hallucinations, cognitive disorganization, grandiosity, and anhedonia) and regularity of tobacco use. Parents rated the twins' negative symptoms. Regression analyses were conducted while adjusted for sociodemographic characteristics, prenatal maternal smoking, cannabis use, sleep disturbance, and stressful life events. Bivariate twin modeling was used to estimate the degree of genetic and common and unique environmental influences shared between tobacco use and PE.
RESULTS
Regular smokers were significantly more likely to experience paranoia, hallucinations, cognitive disorganization, and negative symptoms (β = 0.17-0.34), but not grandiosity or anhedonia, than nonsmokers, after adjustment for confounders. Paranoia, hallucinations, and cognitive disorganization correlated ≥0.15 with tobacco use (r = 0.15-0.21, all p < .001). Significant genetic correlations (r=0.37-0.45) were found. Genetic influences accounted for most of the association between tobacco use and paranoia (84%) and cognitive disorganization (81%). Familial influences accounted for 80% of the association between tobacco use and hallucinations.
CONCLUSION
Tobacco use and PE during adolescence were associated after adjustment for confounders. They appear to co-occur largely because of shared genetic influences.
Topics: Adolescent; Female; Genetic Predisposition to Disease; Hallucinations; Humans; Male; Psychotic Disorders; Regression Analysis; Tobacco Use; Twins, Dizygotic; Twins, Monozygotic; United Kingdom
PubMed: 30738553
DOI: 10.1016/j.jaac.2018.06.037 -
Human Reproduction (Oxford, England) Jul 2020Does having a male co-twin influence the female twin's reproductive outcomes?
STUDY QUESTION
Does having a male co-twin influence the female twin's reproductive outcomes?
SUMMARY ANSWER
Women with a male co-twin had the same chances of being pregnant and having children compared to same-sex twin pairs.
WHAT IS KNOWN ALREADY
According to the twin testosterone transfer (TTT) hypothesis, in an opposite-sex twin pregnancy, testosterone transfer from the male to the female co-twin occurs. A large body of literature supports the negative impact of prenatal testosterone exposure on female's reproductive health in animal models; however, evidence from human studies remains controversial.
STUDY DESIGN, SIZE, DURATION
This cohort study included all dizygotic female twins in the Aberdeen Maternity and Neonatal Databank (Scotland) born before 1 January 1979. The 317 eligible women were followed up for 40 years for any pregnancies and the outcome of those pregnancies recorded in the same database.
PARTICIPANTS/MATERIALS, SETTING, METHODS
Fertility outcomes (number of pregnancies, number of livebirths and age at first pregnancy) were compared between women with a male co-twin (exposed group, n = 151) and those with a female co-twin (unexposed group, n = 166). Population averaged models were used to estimate odds ratios (OR) and 95% CI for all outcomes with adjusting for potential confounders.
MAIN RESULTS AND THE ROLE OF CHANCE
There were no differences in chances of having pregnancies (adj. OR 1.33; 95% CI 0.72, 2.45) and livebirths (adj. OR 1.22; 95% CI 0.68, 2.18) between women from same-sex and opposite-sex twin pairs. Women with a male co-twin were more likely to smoke during pregnancy and, in the unadjusted model, were younger at their first pregnancy (OR 2.13; 95% CI 1.21, 3.75). After adjusting for confounding variables (year of birth and smoking status) the latter finding was no longer significant (OR 1.67; 95% CI 0.90, 3.20).
LIMITATIONS, REASONS FOR CAUTION
The dataset was relatively small. For women without a pregnancy recorded in the databank, we assumed that they had not been pregnant.
WIDER IMPLICATIONS OF THE FINDINGS
Despite the evidence from animal studies concerning the adverse effects of prenatal testosterone exposure on female health, our results do not support the TTT hypothesis. The finding that women with a male co-twin are more likely to smoke during pregnancy highlights the importance of considering post-socialisation and social effects in twin studies.
STUDY FUNDING/COMPETING INTEREST(S)
European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie project PROTECTED (grant agreement No. 722634) and FREIA project (grant agreement No. 825100). No competing interests.
TRIAL REGISTRATION NUMBER
N/A.
Topics: Child; Cohort Studies; Female; Humans; Male; Pregnancy; Pregnancy, Twin; Scotland; Testosterone; Twins, Dizygotic
PubMed: 32558884
DOI: 10.1093/humrep/deaa091