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Twin Pairs Discordant (twin + pair_discordant)
Selected AbstractsEarly cannabis use and DSM-IV nicotine dependence: a twin studyADDICTION, Issue 11 2008Arpana Agrawal ABSTRACT Background Evidence suggests that cannabis users are at increased risk for cigarette smoking,if so, this may potentially be the single most alarming public health challenge posed by cannabis use. We examine whether cannabis use prior to age 17 years is associated with an increased likelihood of DSM-IV nicotine dependence and the extent to which genetic and environmental factors contribute to this association. Methods A population-based cohort of 24,36-year-old Australian male and female twins (n = 6257, 286 and 229 discordant pairs) was used. The co-twin,control method, with twin pairs discordant for early cannabis use, was used to examine whether, after controlling for genetic and familial environmental background, there was evidence for an additional influence of early cannabis use on DSM-IV nicotine dependence. Bivariate genetic models were fitted to the full data set to quantify the genetic correlation between early cannabis use and nicotine dependence. Results The early cannabis-using twin was about twice as likely to report nicotine dependence, when compared to their co-twin who had experimented with cigarettes but had never used cannabis. Even when analyses were restricted to cannabis users, earlier age cannabis use onset conferred greater risk (1.7) for nicotine dependence than did later onset. This association was governed largely by common genetic liability to early cannabis use and nicotine dependence, as demonstrated by genetic correlations of 0.41,0.52. Conclusions Early-onset cannabis users are at increased risk for nicotine dependence, but this risk is attributable largely to common genetic vulnerability. There is no evidence for a causal relationship between cannabis use and nicotine dependence. [source] A comparison of early family life events amongst monozygotic twin women with lifetime anorexia nervosa, bulimia nervosa, or major depressionINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 8 2007Tracey D Wade PhD Abstract Objectives: To investigate the differential profile of early family life events associated with lifetime anorexia nervosa (AN), bulimia nervosa (BN), and major depression (MD). Method: Only data from the monozygotic twins (n = 622) were examined from a community sample of female twins who had participated in three waves of data collection. Eating disorder and MD diagnoses were ascertained from the Eating Disorder Examination at Wave 3 and interview at Wave 2 respectively. Early family events were ascertained from self-report measures at Waves 1 and 3. Two case control designs were used, including a comparison of women: (1) who had lifetime AN, BN, MD, and controls, and (2) twin pairs discordant for either AN, BN, or MD (where the unaffected cotwin formed the control group). Results: Across the two types of designs, compared to controls, both AN and BN were associated with more comments from the family about weight and shape when growing up. AN was uniquely associated with higher levels of paternal protection while BN was associated with higher levels of parental expectations. Conclusion: While some overlap among early life events was indicated, especially related to parental conflict and criticism, there was evidence to support some degree of nonoverlap among life events associated with AN, BN, and MD. © 2007 by Wiley Periodicals, Inc. Int J Eat Disord 2007 [source] Serum Lipid Levels and Cognitive Change in Late LifeJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 3 2010Chandra A. Reynolds PhD OBJECTIVES: To assess the effect of lipids and lipoproteins on longitudinal cognitive performance and cognitive health in late life and to consider moderating factors such as age and sex that may clarify conflicting prior evidence. DESIGN: Prospective cohort study. SETTING: A 16-year longitudinal study of health and cognitive aging. PARTICIPANTS: Eight hundred nineteen adults from the Swedish Adoption Twin Study of Aging aged 50 and older at first cognitive testing, including 21 twin pairs discordant for dementia. MEASUREMENTS: Up to five occasions of cognitive measurements encompassing verbal, spatial, memory, and perceptual speed domains across a 16-year span; baseline serum lipids and lipoproteins including high-density lipoprotein cholesterol (HDL-C), apolipoprotein (apo)A1, apoB, total serum cholesterol, and triglycerides. RESULTS: The effect of lipids on cognitive change was most evident before age 65. In women, higher HDL-C and lower apoB and triglycerides predicted better maintenance of cognitive abilities, particularly verbal ability and perceptual speed, than age. Lipid values were less predictive of cognitive trajectories in men and, where observed, were in the contrary direction (i.e., higher total cholesterol and apoB values predicted better perceptual speed performance though faster rates of decline). In twin pairs discordant for dementia, higher total cholesterol and apoB levels were observed in the twin who subsequently developed dementia. CONCLUSION: High lipid levels may constitute a more important risk factor for cognitive health before age 65 than after. Findings for women are consistent with clinical recommendations, whereas for men, the findings correspond with earlier age-associated shifts in lipid profiles and the importance of lipid homeostasis to cognitive health. [source] Heritability of Obesity-related Phenotypes and Association with Adiponectin Gene Polymorphisms in the Chinese National Twin RegistryANNALS OF HUMAN GENETICS, Issue 2 2010Juan Lee Summary The purpose of this study was to estimate the heritability of obesity-related phenotypes and investigate the association of adiponectin gene polymorphisms +45T>G and +276G>T with these measures in Chinese twins. 1260 twin pairs were recruited from two cities through the Chinese National Twin Registry System from 2001 to 2005. Two SNPs at the adiponectin locus (+45T>G and +276G>T) were genotyped. Structural equation modeling (SEM) was used to estimate heritability and the best-fitting variance component model. The regular association among all twins was analysed with generalised estimating equations (GEE). Sib-transmission/disequilibrium test (TDT) within dizygotic (DZ) twin pairs discordant for their genotype was performed using SEM. Additive genetic, common and unique environmental (ACE) model-based heritability of body mass index (BMI) was 61%, while additive genetic and unique environmental (AE)-model-based heritability of waist circumference (WC) and waist-hip ratio (WHR) were 75% and 61%, respectively. There was no association of adiponectin gene +45T>G and +276G>T genotypes with obesity-related phenotypes in all twins or discordant DZ twins. Our twins data did not support that there was an association between adiponectin gene polymorphisms +45T>G and +276G>T and the obesity-related phenotypes. Further studies are required to better understand the role of adiponectin gene polymorphisms in obesity. [source] Too early to dismiss Yersinia enterocolitica infection in the aetiology of Graves' disease: evidence from a twin case,control studyCLINICAL ENDOCRINOLOGY, Issue 3 2008Thomas H. Brix Summary Background,Yersinia enterocolitica (YE) infection has long been implicated in the pathogenesis of Graves' disease (GD). The association between YE and GD could, however, also be due to common genetic or environmental factors affecting the development of both YE infection and GD. This potential confounding can be minimized by investigation of twin pairs discordant for GD. Aim, To examine whether YE infection is associated with GD. Design, We first conducted a classical case,control study of individuals with (61) and without (122) GD, and then a case,control study of twin pairs (36) discordant for GD. Methods, Immunoglobulin (Ig)A and IgG antibodies to virulence-associated Yersinia outer membrane proteins (YOPs) were measured. Main outcome measures, The prevalence of YOP IgA and IgG antibodies. Results, Subjects with GD had a higher prevalence of YOP IgA (49%vs. 34%, P = 0·054) and YPO IgG (51%vs. 35%, P = 0·043) than the external controls. The frequency of chronic YE infection, reflected by the presence of both IgA and IgG YOP antibodies, was also higher among cases than controls (49%vs. 33%, P = 0·042). Similar results were found in twin pairs discordant for GD. In the case,control analysis, individuals with GD had an increased odds ratio (OR) of YE infection: IgA 1·84 (95% CI 0·99,3·45) and IgG 1·90 (95% CI 1·02,3·55). In the co-twin analysis, the twin with GD also had an increased OR of YE infection: IgA 5·5 (95% CI 1·21,24·81) and IgG 5·0 (95% CI 1·10,22·81). Conclusion, The finding of an association between GD and YE in the case,control study and within twin pairs discordant for GD supports the notion that YE infection plays an aetiological role in the occurrence of GD, or vice versa. Future studies should examine the temporal relationship of this association in more depth. [source] | ||||||||||