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Twin Design (twin + design)
Selected AbstractsAre there genetic influences on addiction: evidence from family, adoption and twin studiesADDICTION, Issue 7 2008Arpana Agrawal ABSTRACT Aims In this exciting era of gene discovery, we review evidence from family, adoption and twin studies that examine the genetic basis for addiction. With a focus on the classical twin design that utilizes data on monozygotic and dizygotic twins, we discuss support in favor of heritable influences on alcohol, nicotine, cannabis and other illicit drug dependence. Methods We review whether these genetic factors also influence earlier stages (e.g. experimentation) of the addictive process and whether there are genetic influences specific to each psychoactive substance. Results Converging evidence from these studies supports the role of moderate to high genetic influences on addiction with estimates ranging from 0.30 to 0.70. The changing role of these heritable factors as a function of gender, age and cultural characteristics is also discussed. We highlight the importance of the interplay between genes and the environment as it relates to risk for addiction and the utility of the children-of-twins design for emerging studies of gene,environment interaction is presented. Conclusions Despite the advances being made by low-cost high-throughput whole genome association assays, we posit that information garnered from twin studies, especially extended twin designs with power to examine gene,environment interactions, will continue to form the foundation for genomic research. [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] Stability of genetic influence on morningness,eveningness: a cross-sectional examination of South Korean twins from preadolescence to young adulthoodJOURNAL OF SLEEP RESEARCH, Issue 1 2007YOON-MI HUR Abstract A cross-sectional twin design was used to study the developmental nature of genetic and environmental influences on morningness,eveningness (M,E). A total of 977 South Korean twin pairs aged 9,23 years completed 13 items of a Korean version of the Composite Scale through the telephone interview. The total sample was split into three age groups: preadolescents, adolescents, and young adults. Twin correlations did not vary significantly with age, suggesting that genetic influences on M,E are stable throughout the developmental span. Results of model-fitting analyses indicated that genetic and environmental factors explained, respectively, 45% and 55% of the variance in all three age groups. Environmental factors were primarily those factors that twins did not share as a consequence of their common rearing; family environmental factors in M,E were consistently near zero in all three age groups. The present study is the first to demonstrate genetic influences on M,E in preadolescent children as young as 9 years old. In spite of differences in culture and frequencies of genes between South Koreans and Caucasians, genetic and environmental influences on M,E found in the present sample were remarkably similar to those reported by previous studies on the basis of late adolescent and adult Caucasian twins. [source] Gene,environment interactions and alcohol use and dependence: current status and future challengesADDICTION, Issue 6 2009Carmen S. Van Der Zwaluw ABSTRACT Aim To discuss the current status of gene,environment interaction research with regard to alcohol use and dependence. Further, we highlight the difficulties concerning gene,environment studies. Methods Overview of the current evidence for gene,environment interactions in alcohol outcomes, and of the associated challenges in gene,environment studies. Results Attention to the causative roles of gene,environment interactions in alcohol use and dependence is increasing. Studies with twin designs are beginning to examine gene-shared environment effects, and animal studies have investigated gene,environment interaction effects on alcohol intake in primates. Thirteen studies incorporated gene,environment interactions in examining alcohol use or dependence in humans. These studies held a variety of candidate genes and environmental risk factors and their heterogeneity made it impossible to draw firm general conclusions. Conclusions Challenges for future gene,environment studies are abundant, and consist of, for example, the development of clear theoretical assumptions about neurobiological mechanisms and the recruitment of large longitudinal samples that already start in childhood. Replication is essential to prevent an overload of false-positive results. Despite the difficulties, it is crucial to include gene,environment interactions in future studies in order to unravel the aetiological factors of human alcohol outcomes. [source] Are there genetic influences on addiction: evidence from family, adoption and twin studiesADDICTION, Issue 7 2008Arpana Agrawal ABSTRACT Aims In this exciting era of gene discovery, we review evidence from family, adoption and twin studies that examine the genetic basis for addiction. With a focus on the classical twin design that utilizes data on monozygotic and dizygotic twins, we discuss support in favor of heritable influences on alcohol, nicotine, cannabis and other illicit drug dependence. Methods We review whether these genetic factors also influence earlier stages (e.g. experimentation) of the addictive process and whether there are genetic influences specific to each psychoactive substance. Results Converging evidence from these studies supports the role of moderate to high genetic influences on addiction with estimates ranging from 0.30 to 0.70. The changing role of these heritable factors as a function of gender, age and cultural characteristics is also discussed. We highlight the importance of the interplay between genes and the environment as it relates to risk for addiction and the utility of the children-of-twins design for emerging studies of gene,environment interaction is presented. Conclusions Despite the advances being made by low-cost high-throughput whole genome association assays, we posit that information garnered from twin studies, especially extended twin designs with power to examine gene,environment interactions, will continue to form the foundation for genomic research. [source] Loneliness in adolescence: gene × environment interactions involving the serotonin transporter geneTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2010Eeske Van Roekel Background:, Loneliness is assumed to peak in early adolescence and to decrease throughout middle and late adolescence, but longitudinal confirmation of this tendency is lacking. Behavioral genetic studies with twin designs have found a significant genetic component for loneliness in children and adults, but no molecular genetic studies have been conducted to reveal the functional polymorphisms involved. Methods:, Associations among the serotonin transporter gene (5-HTTLPR), sex, parental support, and loneliness were examined in a longitudinal study spanning five annual waves (N = 306). Results:, Using latent growth curve modeling (LGCM), loneliness was found to be highest in early adolescence and slowly declined throughout adolescence. The 5-HTTLPR genotype was related to the development of loneliness, in that short allele carriers remained stable in loneliness over time, whereas adolescents with the long-long genotype decreased in loneliness. Interactions were found between maternal support and 5-HTTLPR genotype, showing that adolescents who perceived little support from their mothers and carried a short allele were at increased risk for developing loneliness. Conclusions:, Our study is the first to chart adolescent loneliness longitudinally and to examine the genetic underpinnings of loneliness. Our results contribute to a further understanding of the environmental and genetic basis of loneliness. Replication of our results is needed in both population-based and clinical samples. [source] | ||||||||||