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  • 1
    Electronic Resource
    Electronic Resource
    Genetics and Developmental Psychopathology: 2. The Main Effects of Genes and Environment on Behavioral Problems in the Virginia Twin Study of Adolescent Behavioral Development (1997)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of child psychology and psychiatry 38 (1997), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1469-7610.1997.tb01614.x
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  • 2
    Electronic Resource
    Electronic Resource
    Genetics and Developmental Psychopathology: 1. Phenotypic Assessment in the Virginia Twin Study of Adolescent Behavioral Development (1997)
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of child psychology and psychiatry 38 (1997), S. 0 
    Details
    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
    URL: http://dx.doi.org/10.1111/j.1469-7610.1997.tb01613.x
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  • 3
    Electronic Resource
    Electronic Resource
    A molecular genetic approach to the identification of isochromosomes of chromosome 21 (1991)
    Springer
    Human genetics 〈Berlin〉 86 (1991), S. 375-382 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The largest class of de novo chromosomal rearrangements in Down syndrome are rea(21q21q). Classically, these rearrangements have been termed Robertsonian translocations, implying an attachment of two different chromosome 21 homologues. Additionally, a Robertsonian translocation between two chromosomes 21 cannot be distinguished from an isochromosome composed of genetically identical arms by cytogenetic analyses. Therefore, we have used molecular techniques to differentiate between true Robertsonian translocations and isochromosomes. Samples were obtained from 12 probands, ascertained for de novo rearrangements between homologous chromosomes 21 [11 rea(21q21q) and 1 rea (21;21)(q22;q22)], their parents (n = 24) and available siblings (n = 7). The parental origins of the de novo rearrangements were assigned using molecular and cytogenetic analyses. Although not statistically significant, there was a two-fold increase in the number of paternally derived de novo rearrangements (n = 8) as compared with maternally derived rearrangements (n = 4). To distinguish between rob(21q21q) and i(21q), we used restriction fragment length polymorphisms (RFLPs) spanning the length of chromosome 21. Using all informative and partially informative RFLPs, we used the method of maximum likelihood to assign the most likely rearrangement definition (i or rob) and parental origin in each family. The maximum likelihood estimates indicated that all rearrangements tested (n = 8) were isochromosomes. C-banding revealed two centromeres in three cases indicating that a U-type exchange occurred between sister chromatids in these rearrangements. Our results suggest that the majority of de novo rea(21q21q) are isochromosomes derived from a single parental chromosome 21.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201838
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  • 4
    Electronic Resource
    Electronic Resource
    Significance of saguaro cactus alkaloids in ecology ofDrosophila mettleri, a soil-breeding, cactophilic drosophilid (1987)
    Springer
    Journal of chemical ecology 13 (1987), S. 2069-2081 
    Details
    ISSN: 1573-1561
    Keywords: Drosophila ; D. mojavensis ; D. nigrospiracula ; D. mettleri ; Diptera ; Drosophilidae ; cactus ; alkaloids ; viability ; development ; longevity ; host-plant relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Drosophila mettleri is a soil-breeding, cactophilic drosophilid which lives in the Sonoran Desert. Several chemical constituents of cacti in this region have been identified as having major roles in insect-host plant relationships involvingDrosophila. For example, isoquinoline alkaloids, which are present in senita cactus, have been shown to be toxic to seven of the nine species tested. The two tolerant species areD. pachea, the normal resident, andD. mettleri. Necroses of senita cacti are often used as feeding substrates byD. mettleri adults, but this species has never been reared from senita rots. Soil, which have been soaked by juice from saguaro and cardón rots, are the typical breeding substrates of this species. The tissues of both of these cacti also contain alkaloids, chemically related to those in senita, but at much lower concentrations. Alkaloid concentration in saguaro-soaked soil was found to be 1.4–27 times the average concentration in fresh tissue. Alkaloids were extracted from saguaro tissue and used in tests of larva-to-adult viability, developmental rate, and adult longevity. Elevated concentrations of saguaro alkaloids had no significant effect on the longevity ofD. mettleri, but significantly reduced the longevity ofD. nigrospiracula andD. mojavensis, two nonsoil breeding cactophilic species. Viability and developmental rates of all three species were affected, but the effect onD. nigrospiracula was comparatively greater. It is argued that the adaptations that allowD. mettleri to utilize the saguaro soil niche also convey tolerance to alkaloids present in senita tissue. The ability to utilize senita necroses as feeding substrates represents an ecological advantage to D. mettleri, in that the density of potential feeding sites is increased as compared to species which are more specific in their host-plant relationships.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01012872
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic Effects on ADHD Symptomatology in 7- to 13-Year-Old Twins: Results from a Telephone Survey (1998)
    Springer
    Behavior genetics 28 (1998), S. 83-99 
    Details
    ISSN: 1573-3297
    Keywords: Attention-deficit hyperactivity disorder ; genetics ; twins ; oppositional-defiant disorder ; conduct disorder ; contrast effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The magnitude of genetic and environmental factors and the influence of contrast effects on attention-deficit hyperactivity disorder (ADHD) symptomatology were examined on a sample of 900 twin pairs, aged 7–13, participating in the Virginia Twin Study of Adolescent Behavioral Development (VTSABD). In addition, the genetic and environmental correlations between ADHD and oppositional-defiant disorder/conduct disorder (ODD/CD) symptomatology were estimated. A series of structural models was applied to maternal ratings from a telephone survey, designed to screen for the three dimensions of ADHD symptomatology (hyperactivity, impulsivity, and inattention) and ODD/CD symptomatology. Model-fitting results suggested that ADHD symptomatology is highly heritable and influenced mostly by additive genetic, specific environmental, and contrast effects. However, this analysis could not exclude with statistical significance additional effects from dominance. The results of the best-fitting bivariate model suggested that the genetic correlation between the two traits is 50% and replicated previous findings of a common genetic factor influencing the comorbidity of ADHD and ODD/CD symptomatologies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021686906396
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  • 6
    Electronic Resource
    Electronic Resource
    A model for comparative ratings in studies of within-family differences (1991)
    Springer
    Behavior genetics 21 (1991), S. 531-536 
    Details
    ISSN: 1573-3297
    Keywords: twins ; siblings ; comparative judgments ; signal detection ; heritability ; Sibling Inventory of Differential Experience (SIDE)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Comparative ratings between pairs of siblings or other relatives are commonly used to refine measures of intrafamily variation. A simple model, based on signal detection theory, is proposed which shows how comparative ratings can be used to estimate within-pair variances of true scores, which can, in turn, be modeled with any of the conventional approaches to partitioning genetic and environmental variance within families.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066679
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  • 7
    Electronic Resource
    Electronic Resource
    The relationship between age at first drug use and teenage drug use liability (1992)
    Springer
    Behavior genetics 22 (1992), S. 197-213 
    Details
    ISSN: 1573-3297
    Keywords: age at onset ; liability ; multidimensional scaling ; multifactorial threshold models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Our analyses of Carey's (1992) simulated data set of substance abuse in a cohort of adolescent twins were aimed at answering the question What is the relationship between age at first drug use andEVER having used drugs (i.e., teenage drug use liability)? Three analytic methods were used to determine whether age at first drug use was (1) a “perfect” index of drug use liability, (2) correlated in relatives but conditionally independent of drug use liability, or (3) causally influenced by drug use liability and by factors independent of liability. The analytic methods included nonmetric multidimensional scaling, multifactorial threshold model-fitting to contingency tables, and pedigree-based likelihood formulations for the raw data. All approaches indicated that age at first drug use was a perfect index of drug use liability. Further, model-fitting results indicated that only shared environmental factors accounted for twin similarity in the onset and timing of drug use. We discuss the limitations of each of the analytic methods and integrate our findings with the true model used in Carey's simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066999
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  • 8
    Electronic Resource
    Electronic Resource
    Analyzing twin resemblance in multisymptom data: Genetic applications of a latent class model for symptoms of conduct disorder in juvenile boys (1993)
    Springer
    Behavior genetics 23 (1993), S. 5-19 
    Details
    ISSN: 1573-3297
    Keywords: Adolescence ; age ; categorical data ; conduct disorder ; development ; etiological heterogeneity ; genotype × environment interaction ; latent class models ; major gene ; segregation analysis ; twins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract A model based on the latent class model is developed for the effects of genes and environment on multivariate categorical data in twins. The model captures many essential features of dimensional and categorical conceptions of complex behavioral phenotypes and can include, as special cases, a variety of major locus models including those that allow for etiological heterogeneity, differential sensitivity of latent classes to measured covariates, and genotype × environment interaction (G×E). Many features of the model are illustrated by an application to ratings on eight items relating to conduct disorder selected from the Rutter Parent Questionnaire (RPQ). Mothers rated their 8-to 16-year-old male twin offspring [174 monozygotic (MZ) and 164 dizygotic (DZ) pairs]. The impact of age on the frequency of reported symptoms was relatively slight. Preliminary latent class analysis suggests that four classes are required to explain the reported behavioral profiles of the individual twins. A more detailed analysis of the pairwise response profiles reveals a significant association between twins for membership of latent classes and that the association is greater in MZ than DZ twins, suggesting that genetic factors played a significant role in class membership. Further analysis shows that the frequencies of MZ pairs discordant for membership of some latent classes are close to zero, while others are definitely not zero. One possible explanation of this finding is that the items reflect underlying etiological heterogeneity, with some response profiles reflecting genetic categories and others revealing a latent environmental risk factor. We explore two “four-class” models for etiological heterogeneity which make different assumptions about the way in which genes and environment interact to produce complex disease phenotypes. The first model allows for genetic heterogeneity that is expressed only in individuals exposed to a high-risk (“predisposing”) environment. The second model allows the environment to differentiate two forms of the disorder in individuals of high genetic risk. The first model fits better than the second, but neither fits as well as the general model for four latent classes associated in twins. The results suggest that a single-locus/two-allele model cannot fit the data on these eight items even when we allow for etiological heterogeneity. The pattern of endorsement probabilities associated with each of the four classes precludes a simple “unidimensional” model for the latent process underlying variation in symptom profile in this population. The extension of the approach to larger pedigrees and to linkage analysis is briefly considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01067550
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