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Spousal Associations for Alcohol Dependence and Educational Attainment. Andrew Williams University of North Carolina. Support from NIH Grants: AA07728, AA11998, AA13321, AA15210. Introduction. Substance abuse associated with low educational attainment
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Spousal Associations for Alcohol Dependence and Educational Attainment Andrew Williams University of North Carolina Support from NIH Grants: AA07728, AA11998, AA13321, AA15210
Introduction • Substance abuse associated with low educational attainment • This association could be linked to familial determinants (genetic and/or environmental) • Likely correlated between spouses • Such factors are of interest because they may lead to an increase in prevalence of alcohol dependence Grant et al., 2007
Research Question To what extent do assortative mating and social homogamy for educational attainment contribute to spousal concordance for alcohol dependence?
Background – Assortative Mating • A process of non-random mating in which individuals select spouses based on characteristics that they and their partner share • “like marries like” – positive AM • “opposites attract” – negative AM • Over time, this can lead to a relative increase in the proportion of variability attributable to genetic factors Grant et al., 2007
Background – Social Homogamy • A social process in which similarities in spouses stem from their correlated environments • Passive influence on mate selection Grant et al., 2007
Sample Information • 6327 individuals from the “1981 cohort” of the Australian Twin Study completed a mailed questionnaire in 1989 • 2995 complete pairs and 337 individuals from twin pairs • 3669 spouses (1356 wives, 2313 husbands) completed a telephone diagnostic interview between 1994-1997
Age and Ethnicity Almost all respondents were of European ancestry
Educational Attainment Variable • 1 = 7 or fewer years of school • 2 = 8-10 years • 3 = 11-12 years • 4 = Apprenticeship or diploma • 5 = Technical or teachers’ college • 6 = University first degree • 7 = University post-graduate degree
Educational Attainment Variable • 1 = 7 or fewer years of school • 2 = 8-10 years • 3 = 11-12 years • 4 = Apprenticeship or diploma • 5 = Technical or teachers’ college • 6 = University first degree • 7 = University post-graduate degree Low Mid High
Assortative Mating Framework MZ=1.0 DZ=0.5(1+μa2) Proportions of Variance a2 =0.76 c2=0.06 e2=0.18 a=0.8705 c=0.2492 e=0.4256 µ=0.5135 MZ and DZ =1.0 A C E E C A a c e e c a µ wife male twin male twin wife µ 1 1 1 1 female spouse self-report male twin self-report male twin self-report female spouse self-report
Social Homogamy Framework a=0.5559 c=0.6921 e=0.4604 m=0.9521 z=0.9999 w=0.0001 Proportions of Variance a2 =0.15 (c+z)2=0.74 e2=0.11 m m ssp s ssp w z C A E C C E A C c a e c c e a c wife male twin male twin wife 1 1 1 1 female spouse self-report male twin self-report male twin self-report female spouse self-report
Alcohol Dependence Variable • Approximated DSM-IV (no clustering with 12-month period) • Prevalences: • Female twins – 4% • Male twins – 18% • Female spouses – 8% • Male spouses – 23%
Alcohol Dependence Correlation Stratified by Education Level Overall Correlation = 0.25
Bivariate Model – Females 0.19* (0.16-0.22) 0.30* (0.17-0.46) 0.37* (0.22-0.53) 0.63* (0.52-0.78) 0.51* (0.38-0.58) * Indicates p<0.05
Bivariate Model – Males 0.21* (0.17-0.27) 0.54* (0.54-0.71) 0.21* (0.11-0.32) 0.46* (0.29-0.58) 0.58* (0.43-0.70) * Indicates p<0.05
Conclusions • Evidence of spousal correlation for educational attainment and alcohol dependence • Educational attainment – cannot distinguish between the contributions of AM and SH, but both may make significant contributions • Bivariate genetic models in twins showed modest evidence of genetic overlap for females and nonshared environment for males
Future Work • Further refinement of social processes for educational attainment is needed • A better approach may be to stratify by education levels and nest assortative mating for alcohol dependence • Larger samples are needed to test suggestive associations in this sample
Acknowledgements • ArpanaAgrawal, Ph.D. • Kathleen K. Bucholz, Ph.D. • Julia D. Grant, Ph.D. • Andrew C. Heath, D.Phil. • Michael T. Lynskey, Ph.D. • Pamela A.F. Madden, Ph.D. • John B. Whitfield, Ph.D. • Nicholas G. Martin, Ph.D.