Effects on sibship size and composition on younger brothers' and sisters' alcohol use initiation : findings from an Australian twin sample

Title from PDF of title page (University of Missouri--Columbia, viewed on September 18, 2012).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Thesis advisor: Dr. Wendy S. SlutskeIncludes bibliographical references.M. A. University of Missouri--Columbia 2012."May 2012"The effects of sibship size and structure on delinquency are well established, but despite strong links between delinquency and alcohol use, the contribution of these factors to drinking behaviors remains largely unexplored. The current study investigated the impact of sibship size and composition on younger brothers' and sisters' ages of drinking and intoxication onset. Large sibship size was hypothesized to facilitate earlier onset in both males and females, and having many older brothers was hypothesized to predict earlier drinking in males and later drinking in females. These hypotheses were tested through a series of statistical investigations performed on information collected from a large Australian twin sample. Results indicated that sibship size and composition effects are strongest when older siblings are close in age. In addition, close in age siblings exerted the strongest effects on drinking when: (1) respondents were from homes of divorce; and (2) they did not have a paternal history of alcohol problems. Potential mechanisms behind these effects and their implications for prevention and intervention are discussed

Age at first use and later substance involvement : characterizing genetic and environmental pathways for tobacco, alcohol, and cannabis /

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Behavioral genetic studies have provided insights into why early substance use initiation is associated with increased risk for disorder. Few genetically-informative studies, however, have operationalized initiation as the timing of first use and simultaneously modeled the timing of initiation and problematic use of multiple substances. Such research can help capture the risk associated with early initiation and determine the extent to which genetic and environmental risk generalizes across substances. This study utilized a behavior genetic approach to examine the relation between the age of substance use initiation and symptoms of substance use disorder. Participants were 7,285 monozygotic and dizygotic twins (40 percent male, mean age at interview equals 30.6) from the Australian Twin Registry who reported on their ages of tobacco, alcohol, and cannabis initiation and symptoms of DSM-IV nicotine dependence, alcohol use disorder, and cannabis use disorder. Biometric modeling was conducted to (a) determine the structure of genetic and environmental influences on initiation and disorder and (b) examine their genetic and environmental overlap. The latent structure of initiation differed across men and women. The familial covariance between initiation and disorder was genetic among men and genetic and environmental among women, suggesting that the relation between first substance use and disorder is partly explained by a shared liability. After accounting for familial overlap, significant unique environmental correlations were observed, indicating that the age of initiation of multiple drugs may directly increase risk for substance-related problems. Results support the utility of conceptualizing initiation in terms of age and of adopting a multivariate approach.Field of study: Psychology.|Dr. Wendy S. Slutske, Dissertation Supervisor.|Includes vita.Includes bibliographical references (pages 159-179)

Genetic and environmental influences on the ages of drinking and gambling initiation: evidence for distinct aetiologies and sex differences. Addiction 2014; 109: 323–31

ABSTRACT Aims To investigate the genetic and environmental contributions to age at first drink (AFD) and age first gambled (AFG), assess their overlap and examine sex differences. Design Univariate twin models were fitted to decompose the variation in AFD and AFG into additive genetic, shared environmental and unique environmental factors. Bivariate genetic models were fitted to assess the genetic and environmental contributions to the sources of covariation in AFD and AFG. Setting National Australian Twin Registry. Participants A total of 4542 same-sex and opposite-sex twins aged 32-43 years, 42% male and 58% female. Measurements AFD and AFG were assessed via structured psychiatric telephone interviews. Age of onset was treated as both continuous and categorical (early/late onset). Findings AFD and AFG were modestly correlated (r = 0.18). Unique environmental influences explained a substantial proportion of the variation in both AFD (0.55, 95% confidence interval [CI] = 0.50-0.61) and AFG (0.66, 95% CI = 0.59-0.72), but these influences were uncorrelated (rE = 0.01). Additive genetic factors explained a notable proportion of variation in AFG (0.21, 95% CI = 0.003-0.39), while shared environmental factors were important for AFD (0.31, 95% CI = 0.15-0.46). Among men, genetic factors influenced variation in AFG but not in AFD and shared environmental factors influenced variation in AFD but not in AFG. Among women, shared environmental factors influenced variation in both AFD and AFG, but these environmental factors were not significantly correlated (rC = 0.09). Conclusions Among Australian twins, age at first drink and age first gambled are influenced by distinct unique environmental factors, and the genetic and environmental underpinnings of both phenotypes differ in men and women

Genetic and environmental influences on the ages of drinking and gambling initiation: evidence for distinct aetiologies and sex differences

AimsTo investigate the genetic and environmental contributions to age at first drink (AFD) and age first gambled (AFG), assess their overlap and examine sex differences

Effects of sibship size and composition on younger brothers' and sisters' alcohol use initiation: findings from an Australian twin sample

Background The effects of sibship size and structure on delinquency are well established. Specifically, having a large family and many brothers has been shown to predict offending. However, despite strong links between delinquency and alcohol use, the contribution of sibship factors to drinking behaviors remains largely unexplored. The current study investigated the impact of sibship size and composition on younger brothers' and sisters' ages of drinking and intoxication onset. Methods We employed a sample of 4,281 same-sex twins from the Australian Twin Register to examine whether (i) large sibship size facilitates earlier age at first drink (AFD) and age at first intoxication (AFI) in males and females, (ii) having many older brothers predicts earlier ages of AFD and AFI in males, and (iii) having many older brothers results in later AFD and AFI in females. We tested whether effects were moderated by parental divorce and alcohol misuse and mediated by familial religion. Results Sibling effects were minimal before accounting for family context. However, when parental divorce and excessive parental drinking were included as moderators, sibling effects were significantly amplified among individuals from homes of divorce, and effects were strongest when siblings were close in age. Conclusions Strong close in age older sibling effects indicate that proximal sibling attitudes and behaviors about alcohol likely interact with structural factors to influence younger siblings' drinking. Sibship factors were much more influential in one population (individuals from homes of divorce) than another (respondents with a parental history of excessive drinking), suggesting that sibling effects vary depending on the type of co-occurring familial risk. Prevention efforts performed at the family level, and introduced before first use of alcohol, are likely to delay drinking initiation and help prevent future alcohol problems