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  • 1
    ISSN: 1469-7610
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Little is known about the contribution of genetic and environmental factors to risk for juvenile psychopathology. The Virginia Twin Study of Adolescent Behavioral Development allows these contributions to be estimated. A population-based, unselected sample of 1412 Caucasian twin pairs aged 8–16 years was ascertained through Virginia schools. Assessment of the children involved semi-structured face-to-face interviews with both twins and both parents using the Child and Adolescent Psychiatric Assessment (CAPA). Self-report questionnaires were also completed by parents, children, and teachers. Measures assessed DSM-III-R symptoms of Attention Deficit Hyperactivity Disorder (ADHD), Conduct Disorder, Oppositional Defiant Disorder, Overanxious Disorder, Separation Anxiety, and Depressive Disorder. Factorially derived questionnaire scales were also extracted. Scores were normalized and standardized by age and sex. Maximum likelihood methods were used to estimate contributions of additive and nonadditive genetic effects, the shared and unique environment, and sibling imitation or contrast effects. Estimates were tested for heterogeneity over sexes. Generally, monozygotic (MZ) twins correlated more highly than dizygotic (DZ) twins, parental ratings more than child ratings, and questionnaire scales more highly than interviews. DZ correlations were very low for measures of ADHD and DZ variances were greater than MZ variances for these variables. Correlations sometimes differed between sexes but those for boy-girl pairs were usually similar to those for like-sex pairs. Most of the measures showed small to moderate additive genetic effects and moderate to large effects of the unique individual environment. Measures of ADHD and related constructs showed marked sibling contrast effects. Some measures of oppositional behavior and conduct disorder showed shared environmental effects. There were marked sex differences in the genetic contribution to separation anxiety, otherwise similar genetic effects appear to be expressed in boys and girls. Effects of rater biases on the genetic analysis are considered. The study supports a widespread influence of genetic factors on risk to adolescent psychopathology and suggests that the contribution of different types of social influence may vary consistently across domains of measurement.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1469-7610
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: We introduce an overlapping cohort sequential longitudinal study of behavioral development and psychopathology in a representative sample of 1412 pairs of twins aged 8 through 16 years. Multiple phenotypic assessments involve a full psychiatric interview with each child and each parent, and supplementary parental, teacher, and child interview material and questionnaires. For the first wave of assessments, the numbers of reported DSM-III-R symptoms of Major Depressive Disorder (MDD), Separation Anxiety Disorder (SAD), Overanxious Disorder (OAD), Oppositional Defiant Disorder (ODD), Conduct Disorder (CD), and Attention Deficit Hyperactivity Disorder (ADHD), assessed through interviews, confirm patterns of age and sex trends found in other epidemiological samples, but underscore their dependence on whether the child or the parent is the informant. Correlations across domains for symptoms reported by the same informant are often as large as correlations across informants for the same domain of symptoms. Factor analyses of these symptom counts, taking account of informant view and unreliability of assessment, show the high degree of correlation between SAD and OAD, between MDD and OAD, and between CD and ODD. ADHD symptoms are relatively independent of the other domains, but show moderate correlations with CD, ODD, and MDD. Factorially derived dimensional questionnaire scales, based on child, parental, and teacher reports, show patterns of relationship to symptom counts consistent with both convergent and discriminant validity as indices of liability to clinical symptoms. Across informants, questionnaire scales provide as good a prediction of symptoms as do clinical interviews. Multitrait-multimethod confirmatory factor analysis reveals the patterns of relationship between symptoms of psychiatric disorder in children taking due account of informant and unique sources of variance. Gender differences are consistent within the correlated clusters of ODD/CD and MDD/SAD/OAD, although there are disorder-specific age trends. There are large informant-specific influences on the reporting of symptoms in clinical interviews. Dimensional questionnaire scales provide a useful source of additional information. In subsequent analyses of genetic and environmental etiology of childhood psychopathology we must expect that results may differ by informant and method of assessment. Multivariate and developmental analyses that explore the sources of these differences will shed new light on the relationship between genetic and environmentally influenced vulnerability and the manifestation of psychopathology in specific circumstances.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-3297
    Keywords: Twins ; twin kinships ; cultural inheritance ; twin environment ; anxiety ; panic ; phobia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Self-report symptoms of anxiety are widely used in mental health and social science research as an index of current psychiatric state. Previous twin studies have suggested that genetic factors account for a significant proportion of the variance in these symptoms. To replicate and extend these findings, we examined self-report symtoms of panic-phobia and somatization in the “Virginia 30,000” twin-family sample. Model fitting applied to 80 unique relationships in the twin-family pedigree produced the following major results: (i) genetic effects were significant for both symptom factors, accounting for between 25 and 49% of the total variance, with the exception of symptoms of panic-phobia in females, where they accounted for 15–16% of the variance; (ii) familial environmental effects were absent for symptoms of somatization, while for symptoms of panic-phobia they accounted for a very small proportion of variance in males (≤1.2%) and a modest proportion in females (6–17%) (iii) spousal correlations were present for both factors, ranging from +0.05 to +0.20; (iv) genetic factors which influenced symptoms were generally the same in males and females, although their effect was greater in males; (v) heritability estimates were lower in the population-based than in the volunteer sample; and (vi) when test-retest reliability was included in the model, results suggest that genetic factors account for at least half of the stable variance for all symptom factors, except panic-phobia in females. Our results support the validity of previous twin studies of self-report symptoms of anxiety and suggest that genetic factors significantly influence these symptoms but familial-environmental factors play little or no etiologic role.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Behavior genetics 25 (1995), S. 589-590 
    ISSN: 1573-3297
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-3297
    Keywords: Educational attainment ; Australian twins ; sex differences ; secular changes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The relative effects of genetic and environmental factors in producing individual differences in educational achievement are compared across women and men and over birth cohorts. In a large sample of Australian twin pairs, the heritability of self-reported educational attainment did not vary among women and men born before and after 1950. In a “psychometric” model of twin resemblance, based on separate self-reports in 1981 and 1989, genetic factors explained 57% of the stable variance in educational achievement, while environmental factors shared by twins accounted for 24% of the variance. Corrections for phenotypic assortative mating for educational level, however, suggested that estimated common-environmental effects could be entirely explained by the correlation between additive genetic values for mates. Taking this into account, heritability of “true” educational attainment in Australia may be as high as 82% with the remaining variation being due to individual environments or experiences. Unlike previous studies in Scandinavian countries, results in Australia suggest that factors influencing educational success are comparable between women and men and for individuals born at different points during this century.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Behavior genetics 29 (1999), S. 155-162 
    ISSN: 1573-3297
    Keywords: Meta-analysis ; categorical phenotypes ; multifactorial threshold model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Meta-analysis of behavioral genetic studies would provide (i) tighter confidence intervals around parameter estimates, (ii) clarification of apparently discrepant study findings, and (iii) a mechanism for analyzing systematic causes of between-study differences. We examined some key issues that arise in the meta-analysis of categorical phenotypes. Data were simulated under a multifactorial threshold model that assumed an underlying normal liability distribution, and summary statistics (probandwise concordance rate, recurrence risk ratio, odds ratio, kappa) compared for given values of the liability correlation between relatives and given population prevalence. Although the odds ratio and kappa statistic performed well at moderate to high values of the population prevalence (15–50%), at low values all of these statistics were sensitive to overall prevalence. In cases where the assumption of a multifactorial threshold model is reasonable, direct estimation of genetic and environmental parameters from the summary statistics from all studies appears to be a preferable strategy. For cases where data from non-randomly ascertained samples are used, the impact of misspecification of the model for ascertainment was examined. For some parameter values, such misspecifications led to quite serious biases to estimates of genetic and environmental parameters. These biases varied in complex ways as a function of research design and of the true causes of variation in the population, so that the same misspecification could lead to an overestimate of the importance of genetic influences in twin data but an underestimation in adoption data or to an overestimate of the importance of genetic effects from twin data if shared environmental as well as genetic influences were simulated but an underestimate of genetic effects if shared environmental effects were assumed unimportant. These complexities emphasize the importance of being sensitive to the effects of misspecifying ascertainment corrections in any meta-analysis of behavioral genetic data.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-3297
    Keywords: Smoking initiation ; quantity smoked ; genetic influences ; Dutch twins ; adolescents ; young adults
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Not much is known about the genetic and environmental determinants of various aspects of substance use in adolescents. This study examined whether the inheritance of initiation of tobacco use in adolescents is independent of the inheritance of the number of cigarettes smoked. Alternative multifactorial threshold models were applied to data on tobacco use in 1676 Dutch adolescent twin pairs. The three models that were considered are (i) the single liability dimension model, (ii) the independent liability dimension model, and (iii) the combined model (CM). The results showed that there is not one underlying continuum of liability to smoking. The CM was the best-fitting model. This model postulates that there are separate initiation and quantity dimensions but allows for the possibility that there are some individuals who are so low on the liability to level of consumption that they are not using tobacco. There were no differences between males and females in the magnitude of the genetic and environmental influences on individual differences in smoking initiation and quantity smoked. Smoking initiation was influenced by genetic factors (39%) and shared environmental influences (54%). Once smoking is initiated genetic factors determine to a large extent (86%) the quantity that is smoked.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-3297
    Keywords: Smoking persistence ; smoking initiation ; cross-cultural ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Using a correlated liability dimensions model, we examined the extent to which the same genetic and environmental factors influence both initiation of regular cigarette smoking and maintenance of the smoking habit in men and women. We analyzed questionnaire survey data obtained from large samples of male and female like-sexed twins from three countries, Australia (N = 1535 pairs), Sweden (N = 5916 pairs), and Finland (N = 4438 pairs), subdivided into three age bands (18–25, 26–35, and 36–46 years of age). We found that familial influences on risk for persistence in smoking cannot be entirely explained by the same factors responsible for risk of smoking initiation. Total genetic variance for smoking persistence varied little by age band and sex (range, 39–49% in women and 42–45% in men); however, even among twins in the youngest group (18–25 years of age), who on average have the fewest years of cigarette use, less than 40% of the total genetic variance in smoking persistence was accounted for by the same genetic factors that increased risk of smoking initiation, and this percentage decreased to less than 10% in the 36–46 year olds.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-3297
    Keywords: Personality ; smoking behavior ; inheritance ; Australian NH&MRC twin panel ; attitudinal variables ; sociodemographic variables
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract In contrast to the extensive research effort to understand the genetic contribution to alcoholism risk, there has been little research directed at understanding genetic influences on smoking behavior. Data from large twin studies in Scandinavia and Australia are consistent with a major genetic influence on the probability that an individual will become a smoker (“initiation”) and will persist in the smoking habit once smoking has started (“persistence”). We use data from the 1988/1989 follow-up survey of the Australian NH&MRC twin panel to determine to what degree personality measures (Tridimensional Personality Questionnaire, Eysenck Personality Questionnaire—Revised) and attitudinal and sociodemographic variables (social and political conservatism, education, religious involvement) might account for genetic or environmental influences on smoking. While we find significant phenotypic associations between these variables and smoking, these are too modest to account for much of the genetic variance. Possible mechanisms by which this genetic variance may arise are discussed.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Behavior genetics 25 (1995), S. 349-356 
    ISSN: 1573-3297
    Keywords: Sensation seeking ; adolescent twins ; multivariate genetic analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The genetic architecture of sensation seeking was analyzed in 1591 adolescent twin pairs. Individual differences in sensation seeking were best explained by a simple additive genetic model. Between 48 and 63% of the total variance in sensation seeking subscales was attributable to genetic factors. There were no sex differences in the magnitude of the genetic and environmental effects. The different dimensions of sensation seeking were moderately correlated. The strongest correlations were between the subscales Thrill and Adventure Seeking and Experience Seeking (r=0.4) and between Boredom Susceptibility and Disinhibition (r=0.4 in males,r=0.5 in females). A triangular decomposition showed that the correlations between the sensation seeking subscales were induced mainly by correlated genetic factors and, to a smaller extent, by correlated unique environmental factors. The genetic and environmental correlation structures differed between males and females. For females, higher genetic correlations for Experience Seeking with Boredom Susceptibility and Disinhibition and higher correlations among the unique environmental factors were found. There was no evidence that sex-specific genes influenced sensation seeking behavior in males and females.
    Type of Medium: Electronic Resource
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