Genetics of parentally reported asthma, eczema and rhinitis in 5-yr-old twins.

The aim of the present study was to examine the genetic and environmental contributions to the individual differences in susceptibility to asthma, eczema and rhinitis in childhood and their role in the association among these conditions. Information on asthma, eczema and rhinitis was obtained by parental report. Parents were asked whether a physician had ever diagnosed the condition. Complete data were available for 8,633 5-yr-old twin pairs born between 1986 and 1998. The frequency of parentally reported asthma, eczema and rhinitis was 8.7, 16.8 and 4.4%, respectively, and was higher in males than females. Genetic factors accounted for ∼90% of the variance in the susceptibility to asthma, eczema and rhinitis. The magnitude of genetic factors did not differ between males and females. The remaining part of the variance was explained by environmental factors not shared by family members. The phenotypic correlations between parentally reported asthma, eczema and rhinitis were moderate and mainly mediated by the same genetic factors. The high heritability and the limited influence of shared environmental factors may point to gene x environment interactions. Future research should focus on this type of interaction processes. Copyright © ERS Journals Ltd 2007

Genetics of the human electroencephalogram (EEG) and event-related brain potentials (ERPs): a review

Twin and family studies of normal variation in the human electroencephalogram (EEG) and event related potentials (ERPs) are reviewed. Most of these studies are characterized by small sample sizes. However, by summarizing these studies in one paper, we may be able to gain some insight into the genetic influences on individual differences in central nervous system functioning that may mediate genetically determined differences in behavior. It is clear that most EEG parameters are to a large extent genetically determined. The results for ERPs are based on a much smaller number of studies and suggest medium to large heritability. © 1994 Springer-Verlag

Genetic and environmental covariation between autistic traits and behavioral problems

Objective: To examine the overlap between autistic traits and other behavioral problems in a general population sample, and explore the extent to which this overlap is due to genetic or environmental factors. Method: Youth Self Report (YSR) data were collected in a general population sample of 424 twin pairs at 18 years of age, and their non twin siblings. In 197 of these twin families, self-report ratings on the Autism-spectrum Quotient (AQ) were collected. Results: Stepwise backward regression analyses revealed that of all 8 YSR syndrome scales, the Withdrawn Behavior (WB) and Social Problems (SOC) scale were the most important predictors of AQ scores, and together with sex, explained 23% of the variance in AQ scores. Genetic structural equation modeling showed that the overlap between AQ and WB and SOC was mainly due to genetic effects. About half of the genetic variance in AQ scores was specific to the AQ, with the remaining half shared with genetic variance in WB and SOC. Conclusions: Endorsement of autistic traits in a general population sample is associated with social and withdrawn behavioral problems and these problems partly share a common genetic etiology with autistic traits. However, most of the variance in AQ scores remains unexplained by YSR scores, and half of the genetic variance in AQ is unshared with WB and SOC. These results indicate that autistic traits have specific characteristics that are substantially genetically independent from other common but related behavioral domains such as social problems and withdrawn behavior

Comparison of Naturally Conceived and IVF-DZ Twins in the Netherlands Twin Registry: A Developmental Study

In a large set of twin pairs, we compared twins born after IVF to naturally conceived twins with respect to birth characteristics, growth, attainment of motor milestones, and emotional and behavioral problems. Twin families were registered with the Netherlands Twin Register. We included 1534 dizygotic (DZ) twins born after IVF, 5315 naturally conceived (NC) DZ twins, and 1504 control NC DZ twins who were matched to the IVF twins based on maternal age, maternal educational level, smoking during pregnancy, gestational age, and offspring sex. Data were obtained by longitudinal surveys sent to fathers, mothers, and teachers at ages 1, 2, 3, 7, 10, and 12 years. Results showed no differences in growth, in attainment of motor milestones, and in behavioral development between IVF and matched NC twins. It can be concluded that for nearly all aspects, development in IVF and NC children is similar

Genetic and environmental influences on cross-gender behavior and relation to behavior problems: A study of Dutch twins at ages 7 and 10 years.

The aim of this study was to investigate the prevalence of cross-gender behavior during childhood, to estimate the influence of genotype and environment on variation in cross-gender behavior, and to explore the association of cross-gender behavior with maternal ratings of behavior problems as indexed by the Internalizing and Externalizing scales of the Child Behavior Checklist (CBCL). Cross-gender behavior was assessed by two items from the CBCL: "behaves like opposite sex" and "wishes to be of opposite sex." As part of an ongoing longitudinal study of the Netherlands Twin Registry, mothers were asked to complete the CBCL for their twins when they were 7 (n∼14,000 twins) and 10 years old (n∼8,500 twins). The prevalence of cross-gender behavior (as measured by maternal report of behaving like or wishing to be the opposite sex) was 3.2% and 5.2% for 7-year-old boys and girls, respectively, and decreased to 2.4% and 3.3% for 10-year-old boys and girls. Surprisingly, the prevalence rate of cross-gender behavior of girls with a male co-twin was lower than of girls with a female co-twin. At both ages, the similarity for cross-gender behavior was greater in monozygotic than in dizygotic twins pairs. Genetic structural equation modeling showed that 70% of the variance in the liability of cross-gender behavior could be explained by genetic factors, at both ages and for both sexes. Cross-gender behavior was associated with higher scores on Internalizing and Externalizing problems, both in boys and in girls. © 2006 Springer Science+Business Media, Inc

Causes of stability of aggression from early childhood to adolescence: A longitudinal genetic analysis in Dutch twins

Aggressive behavior (AGG) in childhood is a stable behavioral trait that persists to a considerable degree into adulthood. For example, Verhulst and van der Ende (1995) investigated the developmental course of proble

Strong Resemblance in the Amplitude of Oscillatory Brain Activity in Monozygotic Twins Is Not Caused by "Trivial" Similarities in the Composition of the Skull

Previous twin studies have shown strong heritability of electroencephalogram amplitude characteristics, such as power spectra. However, it has been suggested that these high heritabilities may reflect "trivial" twin resemblance in intervening tissues such as the skull. Here we demonstrate strong monozygotic twin correlation (0.79 < r < 0.88) of eyes-closed resting-state magnetoencephalogram power, which is insensitive to intervening tissues. These results confirm that brain activity itself is highly heritable. © 2008 Wiley-Liss, Inc