Personality disorders (PDs) reduce global functioning, are associated with high levels of work disability, and are thus also likely to influence long-term sick leave (LTSL). Previous research has indicated significant genetic influence on both DSM-IV PDs and LTSL. To what degree genes contributing to PDs also influence LTSL has not been investigated. The aims of the current study were to investigate which PDs were significantly associated with LTSL, to what extent the genetic contributions to these PDs account for the heritability of LTSL, and to explore the hypothesis of a causal association between PDs and LTSL. The sample consisted of 2,771 young, adult Norwegian twins, born 1967–1979. PDs were assessed using the Structured Interview for DSM-IV Personality (SIDP-IV). The age range for the interview was 20–32. The data were subsequently linked to public records of LTSL (sick leave >16 days) up to 11 years later. The odds ratio for being in the highest LTSL category (>15% sick leave) when fulfilling the DSM-IV criteria for any PD diagnosis was 2.6 (1.8–3.8, 95% CI). Dimensional representations of schizotypal, paranoid, and borderline PD were independently and significantly associated with LTSL. The heritability of LTSL was 0.50. Genetic factors shared with the PDs accounted for 20% of this. The association between PDs and LTSL was due to shared genetic and not environmental influences, and was mainly explained by one common genetic factor. The hypothesis of a causal association was not supported, indicating that the association is explained by overlapping genetic liability between PDs and LTSL.

Background: The study was undertaken to assess the relative contributions of genetic and environmental influences on drunk-driving. Methods: Driving records of a cohort of male and female twins (N = 17,360) from the Mid-Atlantic Twin Registry were examined. Structural equation models were used to estimate the magnitude of genetic and environmental effects on male and female phenotypes, and test for gender differences. Results: There were significant gender and age effects. Compared with females, males were five times more likely to engage in driving under the influence. Among persons aged 21–49 years, the risk for drunk-driving was eight times that for those aged 50+ years and five times greater than those ≤20 years. In both males and females, aged 21–49 years, a large proportion (57%) of the variance in drunk-driving was due to genetic factors and the remaining 43% due to individual specific environmental influences. Conclusions: Drunk-driving is under significant genetic influence in both males and females. Our findings suggest that a different set of genes influence DUIs in men and women.

Despite the importance of dysfunctional attitudes in the development and maintenance of depression, little is known about the etiological origin of dysfunctional attitudes. The Dysfunctional Attitudes Scale for Children was administered to 674 adolescent twins derived from the Beijing Twin Study (BeTwiSt). Four hundred and thirty-nine monozygotic and 235 same-gender dizygotic twin pairs were included. Approximately 54% were females. The age range of the twins was 11–17 years. Model-fitting analyses were conducted. Biometric genetic model-fitting estimates indicated that additive genetic factors accounted for 31% (95% CI: 11%, 45%) of variance in adolescent dysfunctional attitude. The influence of shared environmental factors was small and negligible (9% [95% CI: 0%, 27%]). Non-shared environmental factors explained 60% (95% CI: 55%, 66%) of variance. Equating the estimate parameters across gender or age groups resulted in a non-significant difference of model fit, but there were trends suggesting higher heritability in females and older adolescents. Our results provide evidence for moderate heritability of dysfunctional attitudes in adolescents. Dysfunctional attitudes can be used as an endophenotype to identify risk genes for depression.

The aim of this study was to determine heritability estimates of treatment responses to a 10% hydrogen peroxide strip-based whitening system in twins. Eighty-five twin pairs were randomly assigned to 10% hydrogen peroxide whitening strips or placebo strips without peroxide. Both twins (monozygotic or dizygotic) received the same treatment. Maxillary teeth were treated for 30 minutes twice daily for 7 days. Efficacy was measured objectively as L* (light–dark), a* (red–green), and b* (yellow–blue) color change from digital images at baseline (∆) and day 8. Heritability estimates for tooth whitening treatment responses for changes from day 8 to baseline were obtained using variance-component methodologies. Whitening treatment responses were highly heritable (h2 = 71.0) for ∆b* and ∆a*(p < .0001), but not for ∆L* (h2 = 27.0), which was essentially modulated by environmental factors. This study has demonstrated that both genetic and environmental factors significantly contributed to seven-day whitening treatment responses achieved with 10% hydrogen peroxide strips.

This study investigated the relationship between twin language, twins’ close ties, and social competence in a prospective longitudinal study. We hypothesized that twins whose tie is close would be more likely to develop a twin language, and these twins would be less likely to develop social competence. In addition, we hypothesize that some environmental factors, such as having an older sibling, preschool attendance, zygosity, and sex are also related to twin language, twins’ close ties, and social competence. At baseline in 1999 a mailed questionnaire survey was conducted, and a follow-up questionnaire was distributed in 2004 among 958 mothers. As a result, 516 respondents returned the questionnaire (53.9%). In this study, we used 261 twin pairs aged from 6 to 12 years (school-age children) for analysis, excluding those with missing values. In the present study, we found that zygosity and sex were associated with twins’ close ties. Having an older sibling and preschool attendance did not affect the twins’ close tie, twin language, or social competence. One of the most important findings was that social competence was not affected directly by twins’ close tie, but was affected when a twin language was found.

The management of twin pregnancies discordant for trisomy 21 is dependent on the gestation at diagnosis, chorionicity, and parental preference. Our experience with the management of 15 cases in 1,839 twin pregnancies over a 12-year period is described. Selective termination is not always associated with a successful outcome for the normal co-twin. Two of the three monochorionic twin pregnancies affected by trisomy 21 were discordant. Amniocentesis should be strongly considered rather than chorionic villus sampling in monochorionic twin pregnancies. Pregnancies that continue with a trisomy 21 affected fetus are at risk of polyhydramnios and premature labor.

Objective: The aim of this study was to assess fetal urinary production rates (FUPR) in twin gestations using 3D ultrasonography with VOCAL® (virtual organ computer-aided analysis) and to develop a curve of normal values for the target population. Methods: A cross-sectional study was performed in 30 normal twin pregnancies with gestational ages ranging from 20 to 34 weeks. FUPR was measured using a three-dimensional ultrasound (3D US) virtual organ computer-aided analysis (VOCAL) system. FUPR (ml/hour) was calculated during the filling phase using the equation UPR = (VFB2 - VFB1)/time. The values for UPR were plotted as a function of fetal biometry (biparietal diameter) to generate a nomogram. Results: A total of 41 normal twin fetuses with gestational ages between 20 and 34 weeks were investigated. Eleven were excluded because of inadequate bladder contour image quality and/or the observation of micturition in one or both fetuses. Linear regression analysis of FUPR as a function of biparietal diameter (BPD) shows the normal range for UPR by fetal biometry and is expressed by the following equation: Ln(UPR) = -5.0121 + 0.0548 BPD (R2 0.3386, p value <.001). There was no statistically significant difference when the UPR was stratified by chorionicity. Conclusions: The use of biometric parameters to predict fetal FUPR seems to be useful. In twin pregnancies, BPD is the variable that is most closely related to FUPR. For each 1 mm increase in BPD, there is a 5% increase in FUPR. Chorionicity did not affect FUPR.

Monozygotic (MZ) twinning is generally considered to be rare in species other than human. We inspected sex ratios in European zoo-bred ring-tailed lemurs (Lemur catta), revealing a significant excess of same-sex twins. Of 94 pairs, 60 (64%) were either both males or both females (p = .004). Application of the Weinberg differential rule argues that 27% of all twins in this species are MZ pairs. In this protected species, where twinning is commonplace (~50% of newborns are twins), the probable existence of frequent MZ twinning has ramifications for breeding programs aimed to maximize genetic diversity, and suggests that twin studies in a species other than human could have potential as a medical research tool.

The story of her allegedly stolen twin brother in Armenia is recounted by a ‘singleton twin’ living in the United States. The behavioral consequences and societal implications of this loss are considered. This case is followed by twin research reports on the evolution of sleep length, dental treatment of craniopagus conjoined twins, cryopreserved double embryo transfer (DET), and gender options in multiple pregnancy. Current events include the diagnosis of appendectomy in one identical twin, the accomplishments of autistic twin marathon runners, the power of three-dimensional (3D) facial recognition, and the goals of twin biathletes heading to the 2014 Sochi Olympics in Russia.