Heritability of interests: a twin study

The authors administered inventories of vocational and recreational interests and talents to 924 pairs of twins who had been reared together and to 92 pairs separated in infancy and reared apart. Factor analysis of all 291 items yielded 39 identifiable factors and 11 superfactors. The data indicated that about 50% of interests variance (about two thirds of the stable variance) was associated with genetic variation. The authors show that heritability can be conservatively estimated from the within-pair correlations of adult monozygotic twins reared together. Evidence for nonadditive genetic effects on interests may explain why heritability estimates based on family studies are so much lower. The authors propose a model in which precursor traits of aptitude and personality, in part genetically determined, guide the development of interests through the mechanisms of gene-environment correlation and interaction.     

A twin study of generalized anxiety disorder and major depression

Previous analyses with a sample of female twins sampled from the general population in Virginia have suggested that generalized anxiety disorder (GAD) and major depression (MD) share their genetic determinants but have partly different environmental determinants. The goal of this report is to examine whether these findings apply to samples that include male as well as female twins and contain high proportions of subjects who had been hospitalized for MD. The subjects were ascertained through two different sources: (i) index probands were ascertained through the Swedish Psychiatric Twin Registry for a diagnosis of unipolar or bipolar affective illness; (ii) control twin probands were ascertained through the Swedish Twin Registry. Subjects were sent questionnaires for the assessment of lifetime history of GAD and MD. Positing multinormal distribution of the liability for GAD and MD, we fitted bivariate models to examine the sources of comorbidity. The full model included additive genetic effects, shared environment and individual-specific environment, as well as scalar and non-scalar sex limitations and different thresholds across genders. The best-fitting model included: (i) a genetic correlation of unity; (ii) no common environment; (iii) an individual-specific environmental correlation of 0.28; (iv) different thresholds across genders, but neither scalar nor non-scalar sex-limitations. A model that included additive and dominant genetic effects and individual-specific environment, with correlation of unity for both additive and dominant genetic effects, provided an equivalent fit. These analyses confirm that GAD and MD share the same genetic factors but that their environmental determinants are mostly distinct. Moreover, the present report supports the feasibility of combining clinical ascertained and general-population samples into a single bivariate analysis.     

Heritability of facet-level traits in a cross-cultural twin sample: support for a hierarchical model of personality

The common variance among personality traits can be summarized in the factors of the five-factor model, which are known to be heritable. This study examined heritability of the residual specific variance in facet-level traits from the Revised NEO Personality Inventory. Analyses of raw and residual facet scales across Canadian (183 monozygotic [MZ] and 175 dizogotic [DZ] pairs) and German (435 MZ and 205 DZ pairs) twin samples showed genetic and environmental influences of the same type and magnitude across the 2 samples for most facets. Additive genetic effects accounted for 25% to 65% of the reliable specific variance. Results provide strong support for hierarchical models of personality that posit a large number of narrow traits in addition to a few broader trait factors or domains. Facet-level traits are not simply exemplars of the broad factors they define; they are discrete constructs with their own heritable and thus biological basis.     

Heritability estimates from human twin data by incorporating historical prior information

Bayesian methods are commonly used in some analyses of human genetic data, such as segregation and linkage analyses, but they are not typically used for analyses of human twin data. In this paper we develop a scheme for a Bayesian analysis of human twin data. We develop prior elicitation schemes to incorporate historical information. We consider three prior schemes: fully informative, semi-informative and noninformative. We use Markov chain Monte Carlo sampling algorithms to facilitate Bayesian computation and provide detailed implementation schemes. We also develop model diagnostics for assessing the goodness of fit of twin models. Using a simulation study, we show that if the purpose of the study is to estimate the intraclass correlations or heritability in twin studies, then the semi-informative prior is as informative as the fully informative prior. Finally, a real data example is used to illustrate the proposed methodologies.     

A retrospective study of the learning history origins of anxiety sensitivity

Under non-epidemic conditions, Neisseria meningitidis causes disease primarily in children under the age of 5 and the cases are sporadic without any evident relationship between them. Occasionally, localized outbreaks of meningococcal disease occur, and sometimes epidemic waves of disease may spread to several countries or even continents and constitute a pandemic. In the past 10 years or so, population genetic analyses have provided insights into the biology of the bacterium and the epidemiology of meningococcal disease, improving our understanding of the cause of epidemics. Through the application of molecular methods, and especially multilocus enzyme electrophoresis, to N. meningitidis strains of worldwide origin, it has been possible to identify virulent clones and provide a surveillance system to warn of meningococcal epidemics. The characteristics of the predominant clones which are nowadays causing meningococcal disease in the world are summarized here and the importance of population genetics in interpreting the epidemiological data is illustrated.     

Conceptualizations of anxiety sensitivity.

Anxiety sensitivity (fear of anxiety) is thought to play an important role in the development and maintenance of anxiety disorders. One of the most widely used measures of anxiety sensitivity is the Anxiety Sensitivity Index (ASI). The originators of this scale regarded it as a measure of a unidimensional construct (S. Reiss et al, 1986). Recent investigations have challenged this claim, and several 4-factor solutions have been proposed. If the dimension(s) of this scale are to guide theory and research, then it is necessary to determine the most stable factor structure. ASI responses were obtained from 142 spider-phobic college students and 327 psychiatric patients presenting with anxiety or stress-related (psychophysiological) disorders. The results of a series of confirmatory analyses indicated that the ASI is best regarded as unifactorial. The implications for the conceptualization of anxiety sensitivity are considered, and directions for further investigation are set out. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factor structure of a measure of anxiety sensitivity in children

Anxiety sensitivity (i.e., the disposition to react to autonomic arousal with fear) has taken a central role in recent conceptualizations of anxiety. However, questions regarding the dimensional nature of anxiety sensitivity remain. In particular, the factor structure of anxiety sensitivity is unexplored in nonadult populations. The factor structure of the Anxiety Sensitivity Index for Children (ASIC) was examined in three studies. Study 1 (N = 95) used a sample of school children in Grades 4-8 to investigate the reliability of items and factor structure. Items with weak psychometric properties were eliminated, and subsequent analyses revealed that the ASIC was best viewed as a hierarchical scale with a higher order factor (Anxiety Sensitivity) and two first-order factors (Fear of Physiological Arousal and Fear of Mental Catastrophe). Study 2 (N = 112) and Study 3 (N = 144) used more distressed samples of youngsters, and they also found the ASIC to be a hierarchical scale. These findings add a developmental perspective to the Anxiety Sensitivity Index factor analytic discussion and are highly consistent with emergent thinking in the adult anxiety sensitivity literature.     

Antidepressant-associated mania: a study of anxiety disorders patients

ORF3 of the cytoplasmic linear plasmid pGKL2 was disrupted in vivo by integration of a selectable marker. Long-term cultivation of transformants carrying hybrid plasmids with a disrupted ORF3 under selective pressure did not deprive strains of the native counterpart, thereby proving its essentiality for pGKL2 replication and maintenance. The predicted ORF3 polypeptide was found to contain conserved motifs acquainted with mRNA-capping enzymes in the required order, just as in cytoplasmic viruses; new conserved motifs were also identified.     

Review: the Michigan cleft twin study

The combined effects of clefting of the lip and/or palate and of their surgical repair have been examined for a cross-sectional sample of 20 MZ and 25 DZ like-sexed twins discordant for clefting, in the age range of 4 to 17 years. The findings of four studies published since 1975 on that sample are explored for the primary, contiguous and pleiotropic effects of clefting. The primary effects on facial structures of repaired cleft lip appear to be minimal. However, for twins with repaired cleft of the palate (with or without cleft of the lip), the maxilla was both deficient antero-posteriorly and was positioned more posteriorly than in their non-cleft co-twins. The maxillary first molars were usually slightly less erupted in the cleft twins than in the non-cleft twins. The cleft palate only twins had larger cranial base angles than their non-cleft co-twins. A contiguous effect of the posteriorly positioned maxilla was a mandibular rotation downward and backward in the cleft palate and bilateral cleft lip and palate groups but not in the unilateral cleft lip and palate group. The slightly larger cranial base angles found for cleft palate only, although contiguous in location, are more likely pleiotropic effect. The pleiotropic effects include a deficit in height and weight for cleft subjects which appears only after puberty. Although the teeth of the cleft twins tended to be smaller than those of the non-cleft twins, the amount was not clinically significant.     

Childhood history of anxiety in adults with panic disorder: association with anxiety sensitivity and comorbidity

Converging lines of evidence indicate a nonspecific link between childhood anxiety disorders and adult panic disorder. Anxiety sensitivity, defined as the fear of anxiety symptoms, was hypothesized to be a potential mediating variable in this link. This study examined the association among childhood history of anxiety disorders, current anxiety symptoms, and anxiety sensitivity in a sample of 100 patients with panic disorder undergoing treatment. Fifty-five percent of the patients had histories of one or more childhood anxiety disorders. Despite the heterogeneity of symptoms and treatment interventions among these patients, a childhood history of anxiety was associated with comorbid anxiety conditions, agoraphobic avoidance, and anxiety sensitivity scores. Anxiety sensitivity was itself a significant predictor of current severity of illness, but a childhood history of anxiety was not. These findings are consistent with the hypothesis that having an anxiety disorder during childhood is linked with patterns of anxiety and phobic avoidance in adulthood, including the level of anxiety sensitivity in patients with panic disorder.     

Meta-analysis of the relations of anxiety sensitivity to the depressive and anxiety disorders.

There is a substantial literature relating the personality trait anxiety sensitivity (AS; tendency to fear anxiety-related sensations) and its lower order dimensions to the mood and anxiety (i.e., internalizing) disorders. However, particularly given the disorders’ high comorbidity rates, it remains unclear whether AS is broadly related to these disorders or if it shows a pattern of differential relations. Meta-analyses of the concurrent relations of AS with the internalizing disorders were conducted based on 117 studies and 792 effect sizes. Mean Anxiety Sensitivity Index scores by diagnostic group and AS–symptom correlations both indicated that AS is most strongly related to panic, generalized anxiety disorder (GAD), and posttraumatic stress disorder (PTSD). More specific analyses were also conducted on (a) AS correlations with symptom dimensions within individual disorders and (b) correlations between lower order AS components and symptoms. The meta-analytic correlation matrix for higher order AS–disorder relations was submitted to path analysis, modeling latent Distress disorders and Fear disorders that control for much of the shared variance among the disorders. Results of the path analysis indicated that AS is broadly related to these disorders but that agoraphobia, GAD, panic, and PTSD have the strongest associations. In addition, AS was more strongly related to the latent distress disorders than the fear disorders. Because of the contemporaneous assessment of AS and internalizing disorders in these studies, the results should not be taken to mean that AS has a stronger casual association with certain disorders. Implications for concurrent AS–internalizing relations, interpretations of the AS construct, and structural models of personality and psychopathology are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention-deficit hyperactivity disorder: a category or a continuum? Genetic analysis of a large-scale twin study

The improvement of preoperative imaging techniques gets hepatic surgery easier making it more safer and effective. The authors describe the most common hepatic pathologies, benign and malignant, pointing out for each one the principal diagnostic appearances achievable with, the several techniques and, collating these last between them, they optimize the diagnostic-curative pathways for several pathologies. Beyond allowing the diagnosis of the lesion's nature, an important role of the imaging modalities is also to evaluate the resectability of single lesion, weighing up its exact location and the impact on the vascular system esteeming, finally, the volume of remnant liver in case of larger resections. The intra- and extrahepatic, preoperative staging, of the varied hepatic lesions, primitive and secondary, performed comparing the most modern diagnostics techniques, results to be dramatically important arterial portography during, CT (CTAP), contrast-enhanced helical CT, MR imaging. For each patient it's possible to plan the most adequate treatment to his pathology.     

A cotwin control study and a twin study of reflection-impulsivity in children.

Examined the modifiability and heritability of reflection-impulsivity as measured by Matching Familiar Figures. A co-twin control study of 3 pairs of 4-yr-old identical twins was conducted to study the modifiability of the trait. The heritability of the trait was investigated by a twin study of 54 pairs of 3- to 6-yr-old twins. The co-twin study suggests little modifiability of reflection-impulsivity, and the twin study suggests that some of the resistance to change may be due to genetic factors. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A twin study of mathematics disability

Although results obtained from recent twin and adoption studies suggest that individual differences in mathematics performance are due in part to heritable influences, no genetic analysis of mathematics disability (MD) has been previously reported. In this article we present data from the first twin sample ascertained for mathematics deficits (40 identical and 23 same-sex fraternal twin pairs in which at least one member had MD). When mathematics performance data from these twin pairs were subjected to a multiple regression analysis, evidence for a significant genetic etiology was obtained. However, tests for the differential etiology of MD as a function of reading performance level were nonsignificant. Results of this first twin study of MD indicate that the condition is significantly heritable, but data from additional twin pairs will be required to test hypotheses of differential etiology more rigorously.     

A longitudinal investigation of anxiety sensitivity in adolescence.

This investigation sought to expand existing knowledge of anxiety sensitivity in a sample of high school students (N = 2,365) assessed over 4 years. The stability of anxiety sensitivity levels across assessment periods was examined, and cluster analyses were used to identify different developmental pathways in levels of anxiety sensitivity. Groups of adolescents with stable low, stable high, and escalating anxiety sensitivity levels were identified. Adolescents with stable high or escalating anxiety sensitivity were significantly more likely to report experiencing a panic attack than individuals with stable low anxiety sensitivity. Results also indicated that Asian and Hispanic adolescents tended to report higher anxiety sensitivity but that their anxiety sensitivity was less strongly associated with panic than that of Caucasian adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Children's methods of coping with stress: a twin study of genetic and environmental influences

The relative importance of environmental and hereditary factors in how children cope with stress was examined. Emotion-focused, problem-focused, and additional coping variables were assessed in 44 monozygotic (MZ) and 30 dizygotic (DZ) twin pairs, aged 9-16 years. The effects of heritability, shared environment, and unshared environment were examined in structural modelling analyses. Genetic factors accounted for a majority of the reliable variance in four of seven coping variables, while effects of twins' shared environment were negligible for all but one coping variable. Environmental factors important to individual differences in coping strategies were primarily unique to each child (unshared between the twins), highlighting the importance of individual experiences in shaping coping behaviors.     

Latent class and factor analysis of DSM-IV ADHD: a twin study of female adolescents

OBJECTIVE: In an attempt to validate the current DSM-IV criteria for attention-deficit/hyperactivity disorder (ADHD) in females and to determine whether symptoms are continuously distributed or categorically discrete, the authors performed factor and latent class analysis on ADHD symptom data from a large general population of adolescent female twins (1,629 pairs). METHOD: A structured diagnostic assessment of DSM-IV ADHD was completed with at least one parent of 1,629 pairs by telephone. ADHD symptoms from 1,549 pairs were subjected to latent class and factor analysis. RESULTS: Latent class and factor analyses were consistent with the presence of separate continuous domains of inattention (ATT), hyperactivity-impulsivity (H-I), and combined ATT with H-I problems. Severe latent classes corresponding to the predominantly inattentive, predominantly hyperactive-impulsive, and combined types were identified with lifetime prevalence estimates of 4.0%, 2.2%, and 3.7%, respectively. Membership in the severe ATT class predicted academic problems, family problems, and referral to health care providers. Membership in the H-I and combined classes also predicted impaired social relationships. CONCLUSIONS: These results suggest that DSM-IV ADHD subtypes can be thought of as existing on separate continua of inattention, hyperactivity-impulsivity, and combined type problems. Membership in any of there severe ADHD latent classes did not preclude academic excellence, but it was associated with different types of impairment and health care-seeking behavior. These data have implications in the areas of diagnosis, classification, treatment, and research.     

The relation between anxiety sensitivity and depression in children and adolescents referred for anxiety

Research conducted with adult samples suggests that anxiety sensitivity is positively related to depression (Otto et al., 1995, Journal of Anxiety Disorders, 10, 117-123). The Childhood Anxiety Sensitivity Index (CASI, Silverman et al., 1991, Journal of Clinical Child Psychology, 20 162-168) was used in this study to provide an examination of the relation between anxiety, anxiety sensitivity, and depression in a sample of children and adolescents (N = 234) referred for anxiety disorders. A significant correlation between depression and anxiety sensitivity was found. This relation remained statistically significant when controlling for other aspects of anxiety (i.e. worry, physiological anxiety, and concentration). The similarities between these findings and findings obtained with adults are discussed, as well as suggestions for future research.     

Use of health services for anxiety disorders: a multisite study in Quebec

OBJECTIVE: We investigated patient characteristics and use of services for anxiety disorders among patients seeking care from participating clinicians at 7 anxiety clinics in Quebec: 3 general hospital clinics, 3 psychologist-run clinics, and one psychiatric hospital clinic. METHODS: Persons eligible for the study were those who were visiting the clinics for the first time, had a current diagnosis of an anxiety disorder, and could communicate in French or English. Subjects recruited through advertisements were excluded. Data, collected by a self-administered questionnaire, included demographics, treatment history, use of services for anxiety, and the Beck Anxiety Inventory (BAI). RESULTS: The sample comprised 235 subjects: 146 seen at 3 general hospital clinics, 54 at 3 psychologist-run clinics, and 35 at a psychiatric hospital clinic. There were statistically significant differences by clinic type in the prevalence of specific anxiety diagnoses, BAI score, referral source, antidepressant use, and use of services. High-intensity use (10 or more consultations during the previous year) was reported by 23.4% of the sample for medical services and 19.6% for mental health services. Multiple logistic regression identified variables associated with high-intensity use of medical services (higher BAI score, 1 to 4 years since first sought treatment, and less than 12 years of education) and high-intensity use of mental health services (clinic type, obsessive-compulsive disorder [OCD], and 5 or more years since first sought treatment). CONCLUSIONS: The patient populations seen at different types of anxiety clinics differ in several respects, including referral source, previous treatment, and severity of symptoms. Regardless of type of clinic, patients with a longer time since they first sought treatment use more services, particularly mental health services. Those with less education use more medical services than those with greater education.