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The present study examines the relations between adolescent motherhood and children's behavior, substance use, and internalizing problems in a sample of 1,368 children of 712 female twins from Australia. Adolescent motherhood remained significantly associated with all mental health problems, even when using a quasiexperimental design capable of controlling for genetic and environmental confounds. However, the relation between adolescent motherhood and offspring behavior problems and substance use was partially confounded by family background variables that influence both generations. The results are consistent with a causal relation between adolescent motherhood and offspring mental health problems, and they highlight the usefulness of behavior genetic designs when examining putative environmental risks for the development of psychopathology. The generalizability of these results to the United States, which has a higher adolescent birth rate, is discussed. Keywords: adolescent motherhood, children-of-twins, teenage pregnancy, internalizing, externalizing

Objective: The purpose of this study was to estimate associations between early-onset alcohol use/intoxication and subsequent risks of alcohol-related driving risks in young women after control for familial liability for these behaviors. Method: Self-reported data on alcohol use and associated risks were collected from a representative sample of 3,786 Missouri-born adolescent female twins. Results: Alter statistical control for familial liability to alcohol-related driving risks, alcohol dependence, and length of exposure to risk (i.e., time between the earlier of age at onset of drinking or age 16 [the minimum legal driving age in Missouri]), young women who reported early-onset alcohol use/intoxication had odds of alcohol-related driving risks that were from 1.6 to 2.2 times higher than those with a later onset of alcohol use or intoxication. Conclusions: Young women who commence drinking at an early age are at heightened risks for subsequent alcohol-related driving risks, and these associations cannot be explained entirely by familial liability for these behaviors., MOTOR VEHICLE ACCIDENTS ARE one of the leading causes of mortality among youth, and driving while intoxicated remains one of the principal factors associated with accident risk, with estimates suggesting [...]

BACKGROUND: Lead is an environmental pollutant that causes acute and chronic toxicity. Surveys have related mean blood lead concentrations to exogenous sources, including industrial activity, use of lead-based paints, or traffic density. However, there has been little investigation of individual differences in lead absorption, distribution, or toxicity, or of genetic causes of such variation. OBJECTIVES: We assessed the genetic contribution to variation in blood lead concentration in adults and conducted a preliminary search for genes producing such variation. METHODS: Erythrocyte lead concentration was measured by inductively coupled plasma mass spectrometry in venous blood samples from 2,926 Australian adult male and female twins. Mean lead concentrations were compared by place of residence, social class and education, and by the subjects' age, sex, alcohol intake, smoking habits, iron status, and HFE genotype. RESULTS: After adjustment for these covariates, there was strong evidence of genetic effects but not for shared environmental effects persisting into adult life. Linkage analysis showed suggestive evidence (logarithm of odds = 2.63, genome-wide p = 0.170) for a quantitative trait locus affecting blood lead values on chromosome 3 with the linkage peak close to SLC4A7, a gene whose product affects lead transport. CONCLUSIONS: We conclude that genetic variation plays a significant role in determining lead absorption, lead distribution within the body, or both. KEY WORDS: blood lead, heritability, linkage, toxicogenetics, twin study. Environ Health Perspect 115:1224-1230 (2007). doi:10.1289/ehp.8847 available via http://dx.doi.org/ [Online 14 June 2007] John B. Whitfield, Veronica Dy, Robert McQuilty, Gu Zhu, Grant W. Montgomery, Manuel A.R. Ferreira, David L. Duffy, Michael C. Neale, Bas T. Heijmans, Andrew C. Heath, and Nicholas G. Martin (1)Department of Clinical Biochemistry, Royal Prince Alfred Hospital, Sydney, Australia; (2)Genetic Epidemiology Unit, Queensland Institute of Medical Research, Brisbane, Australia; (3)Department of Psychiatry and Human Genetics, Virginia Commonwealth University, Richmond, Virginia, USA; (4)Section of Molecular Epidemiology, Leiden University Medical Center, Leiden, the Netherlands; (5)Missouri Alcoholism Research Center, Department of Psychiatry, Washington University School of Medicine, St. Louis, Missouri, USA, Many elements and compounds present in the environment pose significant health risks to exposed individuals, and contribute to the burden of disease for society. For any exposed person the outcome [...]

A genomewide linkage screen of simple heavy-smoking quantitative trait is conducted using two independent samples. The study found significant evidence of linkage to chromosome 20 in the Finnish sample.

Genome scans are conducted in large samples of dizygotic (DZ) twins from Australia and The Netherlands in order to estimate allele sharing in DZ twins and also to determine whether there is evidence of transmission distortion around the HLA locus or in other chromosomal regions. The results have shown that gene-mapping studies based on affected sibling pairs that include DZ pairs will not suffer from false-positive results due to loci involved in embryo survival.

Objective: Using an offspring-of-twins design, we tested the hypothesis that exposure to paternal alcoholism during the child's first 12 years will increase offspring risk for subsequent alcohol-use disorders (AUD). Method: Structured psychiatric interviews assessed history of psychiatric and substance-use disorders in Vietnam Era Twin Registry fathers (n = 512), their offspring (n = 877), and mothers of the offspring (n = 507). Exposure was defined as the fathers' endorsement of any Diagnostic and Statistical Manual of Mental Disorders (DSM), Fourth Edition, AUD symptom, according to the Lifetime Drinking History assessment (administered in 1999), at any time between offspring ages 0-12 years; all fathers had satisfied DSM, Third Edition, Revised (DSM-III-R), criteria for alcohol dependence in a 1992 diagnostic interview. Cox proportional hazards models were fit to predict time to first symptom of abuse/dependence in offspring. Results: Offspring exposed to paternal alcoholism were significantly more likely to develop an AUD when compared with offspring of nonalcoholic fathers (hazard ratio [HR] = 1.51; 95% confidence interval [CI]: 1.10-2.07). Although offspring unexposed to paternal alcoholism did not significantly differ from control offspring (HR = 1.50, 95% CI: 0.93-2.41), the magnitude of association was similar to that in the exposed offspring. There were no significant differences in AUD between offspring of alcoholics who were exposed and those who were not exposed to paternal alcoholism, as long as fathers had satisfied DSM-III-R criteria for alcohol dependence at some point in their lives. Conclusions: There does not appear to be a relationship between exposure to paternal alcoholism during childhood and development of an AUD in offspring. Genetic and high-risk environmental factors that are correlated with lifetime paternal alcoholism may be stronger predictors of offspring AUD than fathers' problem drinking. Future research should be encouraged, using more comprehensive analyses, to examine the role of family genetic influences and other family environmental influences on offspring alcohol outcomes., CHILDREN OF ALCOHOLICS (COAs) are at an increased risk for developing alcoholism themselves (McGue, 1997; Merikangas and Avenevoli, 2000; Sher, 1997). This association can be explained by both genetic and [...]

Parental divorce is associated with problematic offspring adjustment, but the relation may be due to shared genetic or environmental factors. One way to test for these confounds is to study offspring of twins discordant for divorce. The current analyses used this design to separate the mechanisms responsible for the association between parental divorce, experienced either before or after the age of 16, and offspring well-being. The results were consistent with a causal role of divorce in earlier initiation of sexual intercourse and emotional difficulties, in addition to a greater probability of educational problems, depressed mood, and suicidal ideation. In contrast, the increased risk for cohabitation and earlier initiation of drug use was explained by selection factors, including genetic confounds. Keywords: divorce, children of twins, education, substance use, cohabitation

Parental divorce is associated with a number of emotional and behavioral problems in young-adult offspring, but theoretical and empirical considerations suggest that the relation may be partially or fully accounted for by passive gene-environment correlation or environmental selection characteristics. The current study used the Children of Twins Design to explore whether shared environmental or genetic factors confound the relationship between parental marital instability and measures of psychopathology. Comparisons of the offspring of adult twins in Australia on 3 factors of abnormal behavior, including drug and alcohol, behavioral, and internalizing problems, suggest that environmental influences associated with divorce account for the higher rates of psychopathology. The results are consistent with a causal connection between marital instability and psychopathology in young-adult offspring. Keywords: divorce, behavior genetics, children of twins, externalizing, depression

The association of college attendance with alcohol use and alcohol use disorders was examined in a population-based young adult female twin sample identified from a systematic search of birth records. College-attending women consumed a larger overall volume of alcohol than did their non-college-attending peers, but they were not more likely to be diagnosed with an alcohol use disorder. Significant associations between college attendance and alcohol involvement were probed using 3 different complementary research designs: multivariate cross-sectional analyses, longitudinal analyses of the precollege and college years, and cotwin-control analyses of twin pairs discordant for attending college. Although demographic and lifestyle characteristics accounted for most or all of the association between college attendance and alcohol involvement, there was 1 aspect of drinking behavior, occasionally consuming large quantities of alcohol, that remained significantly associated with college attendance even after controlling for these characteristics or for genetic and family background factors. These results are consistent with the conclusion that some aspect of the college experience may be an important environmental risk factor for this pattern of drinking among young adults.

One of the important components of a flexible pavement structure is granular material layers. Unsaturated granular pavement materials (UGPMs) in these layers influence stresses and strains throughout the pavement structure, and have a large effect on asphalt concrete fatigue and pavement rutting (two of the primary failure mechanisms for flexible pavements). The behavior of UGPMs is dependent on water content, but this effect has been traditionally difficult to quantify using either empirical or mechanistic methods. This paper presents a practical mechanistic framework for determining the behavior of UGPMs within the range of water contents, densities, and stress states likely to be encountered under field conditions. Both soil suction and generated pore pressures are determined and compared to confinement under typical field loading conditions. The framework utilizes a simple soil suction model that has three density-independent parameters, and can be determined using conventional triaxial equipment that is available in many pavement engineering laboratories. DOI: 10.1061/(ASCE)1090-0241(2004)130:9(896) CE Database subject headings: Unsaturated soils; Granular materials; Pavements; Soil suction.

The authors examined genetic and environmental influences, including the contributions of 2 measured aspects of the shared environment of twins (paternal absence, socioeconomic disadvantage) on the development of mother-reported separation anxiety disorder (SAD) history in a sample of 1,887 female twin pairs. Four different symptom categories of SAD were considered. Results revealed that all 4 SAD symptom categories were significantly heritable, whereas the contribution of shared environmental influences to the variation in risk was significant for only 2 of the 4 SAD categories. Paternal absence was found to have an important influence in vulnerability for SAD, whereas the effect of socioeconomic disadvantage was less robust. Evidence for race differences in the etiology of SAD was not found.

Objective: Although epidemiologic studies have reported that problem drinking is associated with nonresponse to surveys, it is unclear whether parents' alcoholism is associated with nonresponse in their offspring. This question is particularly important to family studies of alcoholism. In the current study we constructed a model of offspring nonparticipation in a twin-family design and computed weights to recapture the distribution of offspring alcohol abuse and dependence. Method: In 1999, the first wave of a longitudinal study of offspring of alcoholic twins was conducted via telephone interview with members of the Vietnam Era Twin Registry. The target offspring sample consisted of 2,096 male and female children, of whom 1,270 were successfully interviewed. Offspring response status was classified as participation, refusal or unavailable/no consent. Stepwise logistic regression models were used to identify variables that were significantly associated with one or both types of offspring nonparticipation. A multinomial logit procedure with backward deletion was then used to build a model of the three levels of child response. Results: Paternal alcoholism was not significantly associated with offspring nonresponse, although offspring nonparticipation because of not being located, or being deceased, disabled or unavailable was associated with current paternal smoking, paternal divorce and paternal marital status (after adjustment for other predictor variables). Conclusions: The most important conclusion to be drawn from current results is that the alcohol abuse and dependence history of fathers should not bias analyses in family studies of alcoholism when data are collected via telephone interview. Study limitations and directions for future research are discussed. (1 Stud. Alcohol 65: 140-144, 2004), EPIDEMIOLOGIC STUDIES covering a range of outcome variables have found that sociodemographics, mental health status and substance use and abuse are associated with nonresponse. Nonresponse is simply the loss of [...]

Teenagers who smoke marijuana have a higher risk of using other drugs as they grow older, according to a study of 311 twins, one of whom smoked marijuana whereas the other did not. The twins who smoked marijuana were 2 to 5 times more likely to use other drugs such as cocaine, heroin, and hallucinogens compared to the twins who did not smoke marijuana. This shows that the link between marijuana and other drug use is not entirely genetic or environmental.