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Twin Models (twin + models)
Selected AbstractsEvidence for an Interaction Between Age at First Drink and Genetic Influences on DSM-IV Alcohol Dependence SymptomsALCOHOLISM, Issue 12 2009Arpana Agrawal Background:, Research suggests that individuals who start drinking at an early age are more likely to subsequently develop alcohol dependence. Twin studies have demonstrated that the liability to age at first drink and to alcohol dependence are influenced by common genetic and environmental factors, however, age at first drink may also environmentally mediate increased risk for alcohol dependence. In this study, we examine whether age at first drink moderates genetic and environmental influences, via gene × environment interactions, on DSM-IV alcohol dependence symptoms. Methods:, Using data on 6,257 adult monozygotic and dizygotic male and female twins from Australia, we examined the extent to which age at first drink (i) increased mean alcohol dependence symptoms and (ii) whether the magnitude of additive genetic, shared, and nonshared environmental influences on alcohol dependence symptoms varied as a function of decreasing age. Twin models were fitted in Mx. Results:, Risk for alcohol dependence symptoms increased with decreasing age at first drink. Heritable influences on alcohol dependence symptoms were considerably larger in those who reported an age at first drink prior to 13 years of age. In those with later onset of alcohol use, variance in alcohol dependence was largely attributable to nonshared environmental variance (and measurement error). This evidence for unmeasured gene × measured environment interaction persisted even when controlling for the genetic influences that overlapped between age at first drink and alcohol dependence symptoms. Conclusions:, Early age at first drink may facilitate the expression of genes associated with vulnerability to alcohol dependence symptoms. This is important to consider, not only from a public health standpoint, but also in future genomic studies of alcohol dependence. [source] Genetic and environmental influences on the transmission of parental depression to children's depression and conduct disturbance: an extended Children of Twins studyTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 6 2010Judy L. Silberg Background:, Despite the increased risk of depression and conduct problems in children of depressed parents, the mechanism by which parental depression affects their children's behavioral and emotional functioning is not well understood. The present study was undertaken to determine whether parental depression represents a genuine environmental risk factor in children's psychopathology, or whether children's depression/conduct can be explained as a secondary consequence of the genetic liability transmitted from parents to their offspring. Methods:, Children of Twins (COT) data collected on 2,674 adult female and male twins, their spouses, and 2,940 of their children were used to address whether genetic and/or family environmental factors best account for the association between depression in parents and depression and conduct problems in their children. Data collected on juvenile twins from the Virginia Twin Study of Adolescent Behavioral Development (VTSABD) were also included to estimate child-specific genetic and environmental influences apart from those effects arising from the transmission of the parental depression itself. The fit of alternative Children of Twin models were evaluated using the statistical program Mx. Results:, The most compelling model for the association between parental and juvenile depression was a model of direct environmental risk. Both family environmental and genetic factors accounted for the association between parental depression and child conduct disturbance. Conclusions:, These findings illustrate how a genetically mediated behavior such as parental depression can have both an environmental and genetic impact on children's behavior. We find developmentally specific genetic factors underlying risk to juvenile and adult depression. A shared genetic liability influences both parental depression and juvenile conduct disturbance, implicating child conduct disturbance (CD) as an early indicator of genetic risk for depression in adulthood. In summary, our analyses demonstrate differences in the impact of parental depression on different forms of child psychopathology, and at various stages of development. [source] Body dissatisfaction and drive for thinness in young adult twinsINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 3 2005Anna Keski-Rahkonen MD Abstract Objective We explored correlates of the Eating Disorder Inventory subscales Body Dissatisfaction (BD) and Drive for Thinness (DT) and genetic and environmental influences on these traits. Method In a population-based sample of 4,667 Finnish twins aged 22,27 years, we conducted twin modeling to explore genetic and environmental contributions to body dissatisfaction and drive for thinness. Logistic regression was used for the correlational analysis. Results Various eating and body size-related factors and psychosomatic symptoms were significantly associated with high body dissatisfaction and drive for thinness in both genders. In women, early puberty onset, early initiation of sexual activity, and multiple sex partners were statistically significant risk factors of body dissatisfaction. In gender-specific univariate twin models, additive genes accounted for 59.4% (95% confidence interval [CI] = 53.2,64.7%) of the variance in body dissatisfaction and for 51.0% (95% CI = 43.7,57.5%) of the variance in drive for thinness among females, but for none of the variance among males. Discussion There are very distinct gender differences in the heritability patterns of body dissatisfaction and drive for thinness in young adults. © 2005 by Wiley Periodicals, Inc. [source] The Role of Socioregional Factors in Moderating Genetic Influences on Early Adolescent Behavior Problems and Alcohol UseALCOHOLISM, Issue 10 2009Danielle M. Dick Background:, Twin and family studies have demonstrated that adolescent alcohol use and behavior problems are influenced by a combination of genetic and environmental factors. More recently, studies have begun to investigate how genetic and environmental influences may interact, with efforts underway to identify specific environmental variables that moderate the expression of genetic predispositions. Previously, we have reported that community-level factors, including urban/rural residency, migration rates, and prevalence of young adults, moderate the importance of genetic effects on alcohol use in late adolescence (ages 16 to 18). Here, we extend these findings to test for moderating effects of these socioregional factors on alcohol use and behavior problems assessed in a younger sample of adolescent Finnish twins. Methods:, Using data from the population-based Finnish twin study, FinnTwin12, biometric twin models were fit to data on >1,400 twin pairs to examine the significance of each of the socioregional moderating variables on alcohol use measured at age 14, and behavior problems, measured at age 12. Results:, We find no evidence of a moderating role of these socioregional variables on alcohol use; however, there was significant moderation of genetic influences on behavior problems, with effects limited to girls. Genetic influences assumed greater importance in urban settings, communities with greater migration, and communities with a higher percentage of slightly older adolescents. Conclusions:, The moderation effects observed on behavior problems in early adolescence paralleled the effects found on alcohol use late in adolescence in an independent sample, providing further support for the idea that behavior problems may represent an earlier manifestation of the predisposition to subsequent alcohol problems. Our findings also support the growing body of evidence suggesting that females may be more susceptible to a variety of environmental influences than males. [source] | ||||||||||