Heritability of background EEG across the power spectrum

We estimated the genetic and nongenetic (environmental) contributions to individual differences in the background EEG power spectrum in two age cohorts with mean ages of 26.2 and 49.4 years. Nineteen-lead EEG was recorded with eyes closed from 142 monozygotic and 167 dizygotic twin pairs and their siblings, totaling 760 subjects. We obtained power spectra in 24 bins of 1 Hz ranging from 1.0 to 25.0 Hz. Generally, heritability was highest around the alpha peak frequency and lower in the theta and delta bands. In the beta band heritability gradually decreased with increasing frequency, especially in the temporal regions. Genetic correlations between power in the classical broad bands indicated that half to three-quarters of the genetic variance can be attributed to a common source. We conclude that across the scalp and most of the frequency spectrum, individual differences in adult EEG are largely determined by genetic factors. Copyright © 2005 Society for Psychophysiological Research

Response interference and working memory in 12-year-old children

A group of 69 12-year-old children performed three well-known response interference tasks: the Stroop task, the Eriksen flanker task, and the Simon task. Individual differences in accuracy and speed correlated across the tasks. However, there was no correlation between the interference effects on these three tasks. Stroop interference, but not the Simon or flanker effect, was correlated with working memory capacity, as obtained from the WISC-R. These results may help clarify the nature of ADHD, which is characterized by problems with response interference

Genetic etiology of stability of attention problems in young adulthood

Variation in attention problems in children and adolescents from non-clinical samples is highly heritable. It is unknown how attention problems develop later in life and whether the heritability in the general adult population is the same as in children and adolescents. We assessed the heritability and stability of individual differences in attention problems in the general young adult population and explored to what extent the stability can be attributed to genetic or environmental factors. On one or more occasions, young adult twins (age range, 18-30 years, N = 4,245) from the Netherlands Twin Registry filled out the attention problems (AP) subscale of the Young Adult Self-Report [Achenbach, 1997]: in 1991, N = 1,755 (of which 842 complete pairs), in 1995, N = 2,428 (1156 complete pairs) and in 1997, N = 2,344 (958 pairs). There was only a slight decrease in the average level of attention problems during young adulthood. The heritability at each occasion was around 40%. The correlation of attention problems across a period of 6 years was 0.42, and 77% of this correlation could be ascribed to genetic influences. Thus, individual differences in attention problems in young adulthood are heritable, and stability in individual differences over time can largely be ascribed to genetic influences. Genetic correlations across time were high, suggesting that the genes that influence variability in attention problems in late adolescence are largely the same as those that influence variability in early adulthood. © 2005 Wiley-Liss, Inc

Genomic analyses identify hundreds of variants associated with age at menarche and support a role for puberty timing in cancer risk

The timing of puberty is a highly polygenic childhood trait that is epidemiologically associated with various adult diseases. Using 1000 Genomes Project-imputed genotype data in up to similar to 370,000 women, we identify 389 independent signals (P <5 x 10(-8)) for age at menarche, a milestone in female pubertal development. In Icelandic data, these signals explain similar to 7.4% of the population variance in age at menarche, corresponding to similar to 25% of the estimated heritability. We implicate similar to 250 genes via coding variation or associated expression, demonstrating significant enrichment in neural tissues. Rare variants near the imprinted genes MKRN3 and DLK1 were identified, exhibiting large effects when paternally inherited. Mendelian randomization analyses suggest causal inverse associations, independent of body mass index (BMI), between puberty timing and risks for breast and endometrial cancers in women and prostate cancer in men. In aggregate, our findings highlight the complexity of the genetic regulation of puberty timing and support causal links with cancer susceptibility

Sports participation during adolescence: a shift from environmental to genetic factors

Purpose: A twin design was used to assess the relative contribution of genetic and environmental influences on the variation in sports participation of Dutch male and female twins between the ages of 13 and 20 yr. Methods: Survey data from 2628 complete twin pairs were available (443 male and 652 female monozygotic twin pairs, 377 male and 434 female dizygotic twin pairs, and 722 opposite-sex twin pairs). Subjects were classified as participating in sports if they engaged in competitive or noncompetitive leisure-time sports activities with a minimal intensity of 4 METs for at least 60 min-w

The multi-source interference task: the effect of randomization

Recently a novel interference task was developed, that was aimed at obtaining robust patterns of interference in individual subjects, both behaviorally and neurophysiologically (Bush, Shin, Holmes, Rosen & Vogt, 2003). This multi-source interference task (MSIT) combined elements of spatial and flanker interference, and huge interference effects were obtained in a blocked design. This task could thus in principle be used to assess frontal abnormalities, such as ADHD. In the present study, we further examined the nature of the MSIT. We examined the effect of randomization, and the relative contribution of each type of interference. Using a group of healthy subjects, we found a much smaller interference effect than Bush et al. (2003). In addition, we found that most of the interference could be ascribed to flanker interference, and much less to spatial interference. It seems to be the case that there is a trade-off between obtaining robust and reliable effects, and isolating a specific psychological process. Copyright © Taylor & Francis Ltd

Differential Autonomic Nervous System Reactivity in Depression and Anxiety During Stress Depending on Type of Stressor

Objectives It remains unclear whether depressive and anxiety disorders are associated with hyporeactivity or hyperreactivity of the autonomic nervous system (ANS) and whether deviant reactivity occurs in all types of stressors. This study compared ANS reactivity in people with current or remitted depression/anxiety with reactivity in healthy controls during two stress conditions. Methods From the Netherlands Study of Depression and Anxiety, data of 804 individuals with current depression/anxiety, 913 individuals with remitted depression/anxiety, and 466 healthy controls (mean age = 44.1 years; 66.4% female) were available. Two conditions were used to evoke stress: a) an n-back task, a cognitively challenging stressor, and 2) a psychiatric interview, evoking personal-emotional stress related to the occurrence of symptoms of depression/anxiety. Indicators of ANS activity were heart rate (HR), root mean square of differences between successive interbeat intervals (RMSSD), respiratory sinus arrhythmia (RSA), and preejection period. Results As compared with controls, participants with psychopathology had significant hyporeactivity of HR (controls = 4.1 4.2 beats/min; remitted = 3.5 +/- 3.5 beats/min; current psychopathology = 3.1 +/- 3.4 beats/min), RMSSD (controls = -6.2 +/- 14.5 milliseconds; remitted = -5.4 +/- 17.8 milliseconds; current psychopathology = -3.5 +/- 15.4 milliseconds), and RSA (controls = -9.3 +/- 17.0 milliseconds; remitted = -7.4 +/- 16.5 milliseconds; current psychopathology = -6.9 +/- 15.0 milliseconds) during the n-back task. In contrast, during the psychiatric interview, they showed significant hyperreactivity of HR (controls = 2.7 +/- 3.4 beats/min; remitted = 3.5 +/- 3.4 beats/min; current psychopathology = 4.0 +/- 3.3 beats/min), RMSSD (controls = -3.4 +/- 12.2 milliseconds; remitted = -4.1 +/- 12.1 milliseconds; current psychopathology = -5.6 +/- 11.8 milliseconds), and RSA (controls = -3.8 +/- 8.1 milliseconds; remitted = -4.3 +/- 7.9 milliseconds; current psychopathology = -5.0 +/- 7.9 milliseconds). The lack of group differences in preejection period reactivity suggests that the found effects were driven by altered cardiac vagal reactivity in depression/anxiety. Conclusions The direction of altered ANS reactivity in depressed/anxious patients is dependent on the type of stressor, and only the more ecologically valid stressors may evoke hyperreactivity in these patients

Heritability of life satisfaction in adults: a twin-family study

Background. Subjective well-being (SWB) can be partitioned into the components life satisfaction and affect. Research on factors influencing these components of well-being has mainly focused on environmental characteristics. The aim of this study was to investigate the relative contribution of genes and environment to individual differences in life satisfaction in a large sample of Dutch twins and their singleton siblings. Method. Life satisfaction of 5668 subjects registered with The Netherlands Twin Registry (NTR) was measured with a Dutch version of the self-reported Satisfaction with Life Scale. An extended twin design was used to obtain correlations in life satisfaction scores for monozygotic twins, dizygotic twins and sibling pairs and to estimate the contribution of genes and environment to the variation in life satisfaction. Results. No differences between males and females were found in the mean level of life satisfaction. Broad-sense heritability was 38%. Non-additive genetic factors explained all or most of the genetic influences. The remaining 62% of the variance in life satisfaction could be attributed to unique environmental factors, both persistent and transitory, plus measurement error. Conclusions. Individual differences in life satisfaction are determined in part by genetic factors that are largely or entirely non-additive in nature. © 2005 Cambridge University Press