Showing papers by "Joanne M. Meyer published in 1996"

Genetic influences on DSM-III-R drug abuse and dependence: a study of 3,372 twin pairs.

Abstract: Research and clinical experience indicate that drug use disorders tend to run in families. The objective of this study was to distinguish between the family environment and genetic factors as the source of this observed family resemblance. Data were collected by telephone interview from members of the Vietnam Era Twin Registry, comprising male twin pairs who served in the U.S. military between 1965 and 1975. There were 3,372 pairs in which both twins participated. Drug use disorder was defined as receiving a diagnosis of drug abuse or dependence according to DSM-III-R; 10.1% of the sample had abused or been dependent on at least one illicit drug. A significant difference between concordance rates for monozygotic (26.2%) vs. dizygotic (16.5%) twins indicated a genetic influence on drug use disorder. Biometrical modeling indicated that genetic factors (34% of the variance), the environment shared by twins (28% of the variance), and the nonshared environment (38% of the variance) had significant influences of similar magnitudes on the individual's risk of developing a drug use disorder. These results support the application of molecular genetic approaches to elucidate the genetic influence on drug use disorder, as well as the potential efficacy of environmental intervention to reduce risk.

Genetic and Environmental Influences on the Covariation Between Hyperactivity and Conduct Disturbance in Juvenile Twins

Abstract: Structural equation models were applied to the maternal ratings of 265 MZ and 163 DZ male-male, 347 MZ and 160 DZ female-female, and 262 male-female twin pairs, aged 8-16 years, who participated in the Virginia Twin Study of Adolescent Behavioral Development (VTSABD). Substantial additive genetic influences and contrast effects were found for hyperactivity, and additive genetic and shared environmental effects or positive comparison effects (particularly for the girls) for oppositional/conduct disturbance. Bivariate model fitting showed that the covariation between hyperactivity and oppositional/conduct problems in both younger and older boys and girls is almost entirely attributable to genetic factors. However, whereas in the younger males and females the same set of genes explain all the variation in hyperactivity and conduct disturbance, in the older cohort at least some of the genetic effects are behavior- and gender-specific.

Sex influences on the penetrance of HLA shared-epitope genotypes for rheumatoid arthritis.

Abstract: The association between rheumatoid arthritis (RA) and HLA DRB1 alleles may arise through linkage disequilibrium with a disease locus or the direct involvement of HLA alleles in RA In support of the latter possibility, the shared-epitope hypothesis has been postulated, stating that conformationally similar DR{beta} chains encoded by several DRB1 alleles confer disease susceptibility To examine these alternative hypotheses of marker-disease association and to investigate gender differences in RA susceptibility, we analyzed the distributions of PCR-based DRB1 genotypes of 309 Caucasian RA patients and 283 Caucasian controls Initially, the marker-association-segregation {chi}{sup 2} method was used to evaluate evidence for linkage disequilibrium and the direct involvement of markers DR4 Dw4, DR4 Dw14, and DR1 in RA susceptibility Additional shared-epitope models that grouped DRB1 alleles into five classes (*0401, *0404/*0102, *0405/*0408/*0101, *1001, and all others) and postulated relationships between genotypes and RA susceptibility were also fitted to observed genotypic distributions by the method of minimal {chi}{sup 2} For females, a linkage-disequilibrium model provided a good fit to the data, as did a shared-epitope model with RA most penetrant among individuals with the *0401, *0401 genotype For males, the best model indicated highest RA penetrance among shared-epitope compound heterozygotes Clinically, male RA patientsmore » had more subcutaneous nodules and greater use of slowly acting antirheumatic drugs, while female RA patients had earlier disease onset This study therefore suggests that sex-related factors influence the RA penetrance associated with DRB1 shared-epitope genotypes and that DRB1 effects on RA prognosis and pathogenesis should be considered separately for men and women 67 refs, 7 tabs« less

Heterogeneity among juvenile antisocial behaviours: Findings from the Virginia Twin Study of Adolescent Behavioural Development

Abstract: The examination of heterogeneity in antisocial behaviour was accomplished by applying latent class analytic methods to multivariate categorical data on 389 same-sex male twins, aged 11 to 16 from the Virginia Twin Study of Adolescent Behavioural Development (VTSABD). The data included multiple measures of oppositional and conduct disorder, attention deficit disorder, hyperactivity, impulsivity, reading disability and anxiety from mother, teacher, and child report from both questionnaire and interview (child and adult psychiatric assessment; CAPA). A latent four-class model provided a good fit to the data and yielded four phenotypically and aetiologically distinct latent classes: (1) a non-symptomatic class influenced by both additive genetic and shared environmental factors; (2) a hyperactivity-conduct disturbance class accounted for by both additive and non-additive genetic effects; (3) a 'pure' conduct disturbance class with a very strong shared environmental component; and (4) a multisymptomatic class explained entirely by the additive effect of the genes. Further characterization of these four latent classes by age of the child and parental psychiatric history is also shown.

The Virginia Twin-Family Study of Adolescent Behavioral Development: assessing sample biases in demographic correlates of psychopathology.

Abstract: The Virginia Twin-Family Study of Adolescent Behavioral Development (VTSABD) is a current longitudinal study of psychopathology in 1412 pairs of 8-16-year-old Caucasian twins and their parents. The primary aim of the study is to evaluate family-genetic and environmental risk factors for major domains of psychopathology in families representative of the Virginia Caucasian population. In this report, we utilize census-derived indices of neighbourhood income and urban residence to identify departures from population representation arising at the time of family enrollment in the twin registry and family participation in a psychiatric interview. Furthermore, we consider whether demographic sample biases influenced prevalence rates of adult psychopathology (including major depression, generalized anxiety disorder, alcohol dependence, phobias, and panic disorder) in the VTSABD. Results indicated that families that enrolled in the twin registry (83% of those identified by Virginia schools) and that participated in the home interview (75% of those targeted) resided in urban and rural communities with a range of per capita income levels representative of the Virginia population. However, participation biases operated throughout the study and were primarily characterized by losses of families living in low income, urban communities. There was also a smaller number of families living in high income neighbourhoods that did not enroll in the twin registry or that indefinitely postponed the psychiatric interview. These biases had small effects on prevalence rates of adult psychopathology in the VTSABD sample, even though neighbourhood income was significantly related to a subset of adult diagnoses. We emphasize the usefulness of the census methodology in evaluating sample biases in population-based psychiatric genetic studies.

The Genetics of Children's Oral Reading Performance

Abstract: Measures of reading achievement and verbal ability have been shown to be heritable. Additionally, recent evidence has been suggestive of a major gene effect on reading disability and for problem reading in a sample of normal readers. We report on the etiology of individual differences in oral reading performance, the Slosson Oral Reading Test (SORT), for which biometrical analyses have not been reported in the literature previously. Oral reading performance was measured in a large population-based sample of twins of the Virginia Twin Study of Adolescent Behavioral Development. Biometrical analyses of the SORT suggested that, in both males and females, 69% of the phenotypic variation was due to heritable influences and 13% of the variation due to shared environmental effects. While the relative importance of genetic and environmental influences is equivalent for males and females, males showed greater phenotypic variability than females.

Univariate analysis of dichotomous or ordinal data from twin pairs: A simulation study comparing structural equation modeling and logistic regression

Abstract: The univariate analysis of categorical twin data can be performed using either structural equation modeling (SEM) or logistic regression. This paper presents a comparison between these two methods using a simulation study. Dichotomous and ordinal (three category) twin data are simulated under two different sample sizes (1,000 and 2,000 twin pairs) and according to different additive genetic and common environmental models of phenotypic variation. The two methods are found to be generally comparable in their ability to detect a "correct" model under the specifications of the simulation. Both methods lack power to detect the right model for dichotomous data when the additive genetic effect is low (between 10 and 20%) or medium (between 30 and 40%); the ordinal data simulations produce similar results except for the additive genetic model with medium or high heritability. Neither method could adequately detect a correct model that included a modest common environmental effect (20%) even when the additive genetic effect was large and the sample size included 2,000 twin pairs. The SEM method was found to have better power than logistic regression when there is a medium (30%) or high (50%) additive genetic effect and a modest common environmental effect. Conversely, logistic regression performed better than SEM in correctly detecting additive genetic effects with simulated ordinal data (for both 1,000 and 2,000 pairs) that did not contain modest common environmental effects; in this case the SEM method incorrectly detected a common environmental effect that was not present.