Simulated twin data on substance abuse

Twin data were simulated for use of a new illegal substance. The twin cohort was measured yearly at 10 time intervals during the diffusion of the substance throughout the nation. The models used to generate the data are discussed.This work was supported in part by NIDA Grant DA05131.     

遗传因素和环境因素对儿童亲社会行为影响的双生子研究

目的 应用双生子设计的定量遗传分析方法探讨遗传因素与环境因素对于儿童亲社会行为的影响.方法 使用长处与困难问卷(strengths and difficulties questionnaire,SDQ)家长版本调查了147对成都地区6～16岁双生子的亲社会行为,使用SPSS13.0统计软件、Mx软件进行描述性统计分析、差异性分析、相关分析及遗传分析.结果 (1)除<11岁组外,女性亲社会因子得分显著高于男性(P3<0.05);(2)共享环境因素对儿童亲社会行为的贡献为0.48(95%CI:0.09～0.73),遗传因素的贡献为0.27(95%CI:0～0.66),个体特异性环境因素的贡献为0.25(95%CI:0.18～0.35);(3)女性、家庭实际及理想的亲密度和适应性越好者亲社会行为越好(r:0.17～0.29),而存在孕产期异常情况者、家长管教态度越不一致者亲社会行为越不良(r:-0.16～-0.28).结论 遗传因素和环境因素对儿童的亲社会行为均有影响,年龄和性别与儿童亲社会行为的遗传度相关,影响儿童亲社会行为的环境因素包括家庭功能和教养环境.     

Genetic and environmental effects on Type A scores in monozygotic twin families

Monozygotic (MZ) twin pairs with spouses and children, altogether 787 subjects, completed the Jenkins Activity Survey (JAS). The observed correlations for the various sets of relationships fitted well with biometric models including only parameters for additive genetic effects and, for Type A and Job Involvement, assortative mating. There was no evidence of effects of the family environment (cultural transmission) or genetic dominance (nonadditivity). For all but the Hard Driving and Competitive scale, there was evidence of effects of sex-specific genes. The heritability estimates were, for males and females, respectively, .33 and .39 for Type A, .36 and .48 for Job Involvement, .20 and .52 for Speed and Impatience, and .13 (both sexes) for Hard Driving and Competitive. The estimates given here are deflated by measurement errors and should probably be corrected by multiplying by values in the neighborhood of 1.3. Even after correction, the results suggest that individual differences for Type A and related traits depend more on nonfamilial environment than on genes.     

Association between obesity and asthma in a twin cohort

BACKGROUND: Obesity is linked to asthma in a yet poorly understood manner. We examined the relationship between obesity and asthma in a population-based sample of twins. METHODS: From the cohorts born between 1953 and 1982, who were enrolled in The Danish Twin Registry, a total of 29 183 twin individuals participated in a nationwide questionnaire study, where data on height, weight and asthma were collected. Latent factor models of genetic and environmental effects were fitted using maximum likelihood methods. RESULTS: The age-adjusted risk of asthma was increased both in obese females, OR = 1.96 (1.45-2.64), P < or = 0.001 and in obese males, OR = 1.59 (1.08-2.33), P = 0.02. According to best-fitting models, the heritability for obesity was 81% in males and 92% in females, whereas the heritability for asthma was 78% and 68% in males and females respectively. The age-adjusted genetic liabilities to obesity and asthma were significantly correlated only in females, r = 0.28 (0.16-0.38). CONCLUSIONs: Obese subjects have an increased risk for asthma, which in females seems partly because of common genes.     

Estimates of asthma heritability in a large twin sample

Background Asthma is a complex disease characterized by symptoms of wheezing, shortness of breath, chest tightness, and cough. Objective To study the relative contribution of genetic and environmental factors in the liability to asthma in a large sample of twins. Methods Data on asthma in 21 135 twin pairs, 3–71 years of age, from the Danish Twin Registry were collected via a multidisciplinary questionnaire survey. Heritability estimates were calculated using variance components models. Results A monozygotic twin had an approximately sixfold increased risk of asthma whereas a dizygotic twin only had an approximately threefold increased risk relative to the general population if his or her co‐twin was affected. The difference was more pronounced among males. Familial aggregation of asthma in children and adolescents was explained mainly by additive genetic factors, but common environment was also important. The heritability of asthma was also substantial in adults aged 20–49 years. In older adults (aged 50–71 years), additive genetic factors did not significantly influence the disease risk. Conclusion Genetic influences on asthma are substantial throughout the life span but the proportion of the disease liability explained by genetic factors is decreased in older adults. Cite this as: S. F. Thomsen, S. van der Sluis, K. O. Kyvik, A. Skytthe, V. Backer, Clinical & Experimental Allergy, 2010 (40) 1054–1061.     

Genetic influences on measures of selective attention and speed: A twin study

Measures of selective attention and speed which have been employed in the study of disturbances of cognitive functioning in schizophrenia were used in a study of 20 MZ and 20 DZ normal twin pairs. Results suggest the presence of a genetic contribution to scores on such tasks, particularly for the speed measures.     

Genetic and environmental influences on the development of intelligence

Measures of intelligence were collected in 209 twin pairs at 5, 7, 10, and 12 years of age, as part of a longitudinal project on intelligence, brain function, and behavioral problems. Intelligence was measured at 5, 7, and 10 years of age with the RAKIT, a well-known Dutch intelligence test, consisting of 6 subscales. At 12 years of age, the complete WISC-R was administered (12 subscales). Both intelligence tests resulted in a measure of full-scale IQ (FSIQ). Participation rate is around 93% at age 12. Correlation coefficients over time are high: (r(5–7) = .65; r(5–10) = .65; r(5–12) = .64; r(7–10) = .72; r(7–12) = .69 and r(10–12) = .78). Genetic analyses show significant heritabilities at all ages, with the expected increase of genetic influences and decrease of shared environmental influences over the years. Genetic influences seem to be the main driving force behind continuity in general cognitive ability, represented by a common factor influencing FSIQ at all ages. Shared environmental influences are responsible for stability as well as change in the development of cognitive abilities, represented by a common factor influencing FSIQ at all ages and age-specific influences, respectively.     

血瘦素遗传度的双生子分析

目的　观察遗传因素对血瘦素的影响。方法　 5 7对双生子 ,用微卫星 DNA基因扫描和分型技术 ,根据基因型的一致性来鉴别卵性。双生子间异同比较估计遗传和环境的相对效应 ,用放免法测定血清瘦素。结果　异卵双生子 (dizygotic,DZ)瘦素的对内方差大于同卵双生子 (monozygotic,MZ)的对内方差 (P<0 .0 5 ) ,前者为后者的 2倍多。但当校正体重指数 (body mass index,BMI)、性别和血尿酸 (uricacid,UA)后 ,MZ的对内方差接近于 DZ的对内方差。血瘦素的遗传度 8% ,校正 BMI、性别等的影响后血瘦素的遗传度为 0 .18%。血压与瘦素在简单相关分析时相关 (收缩压 r=0 .35 5 ,P<0 .0 0 1;舒张压 r=0 .339,P<0 .0 0 1) ,多元逐步回归分析时仅 BMI、性别和 UA入选方程 (R2 =0 .788,P<0 .0 0 1)。结论　遗传因素对血瘦素影响不大 ,血瘦素主要受环境因素影响。     

Genetic and Environmental Influences on Transitions in Drug Use

Genetic and environmental factors influence drug abuse, but abuse represents the culmination of a sequence of events. Different levels of use may have different determinants and these determinants may differ across drug types. Approximately 3200 male–male twin pairs from the Vietnam Era Twin Registry were interviewed by telephone. Data were obtained regarding exposure to six categories of illicit drugs, initiation of use, continuation of use, regular usage, and diagnosis of drug abuse/dependence. Genetic, common environmental, and unique environmental influences on transitions of drug involvement, defined as movement from one level of drug use to the next, were investigated. Marijuana had the highest conditional probability for the transition from exposure to use, from use to use more than five times, and from use more than five times to regular use. The rate of transition to regular use of heroin was higher than the rate for amphetamine, cocaine, sedatives, and psychedelics. Cocaine had the highest conditional probability for the transition from regular use to abuse/dependence. Significant genetic influences were observed for a number of transitions in marijuana, amphetamine, and cocaine usage.     

Assessment of heritability for personality,based on a short-form of the Eysenck personality inventory: A study of 12,898 twin pairs

The influence of genetic factors for two personality dimensions was analyzed using data from 12,898 unselected twin pairs of the Swedish Twin Registry. The heritability index was 0.50 (men) and 0.58 (women) for psychosocial instability. Corresponding figures for psychosocial extraversion were 0.54 and 0.66. Thus, about half the phenotypic variation may be attributed to genetic factors.     

遗传与环境因素对儿童内向行为影响的双生子研究

目的 利用双生子设计的定量遗传分析方法探讨遗传因素与环境因素对于儿童内向行为的影响.方法 使用Achenbach儿童行为评定量表家长版本调查了189对成都地区6～16岁双生子的内向行为,采用Holzinger公式计算遗传度,家长评定家庭亲密度和适应性量表、一般健康问卷调查特定环境因素.结果 (1)儿童内向行为遗传度为0.54,年龄、性别与其相关.(2)家庭实际适应性、父母心理健康情况与儿童的内向行为显著相关(r=-0.213,0.250,0.309;Ps＜0.001),母亲心理健康状况为其危险因素(OR=2.483,P=0.008).结论 遗传因素和环境因素对儿童的内向行为均有影响,年龄和性别与遗传度相关,影响儿童内向行为的环境因素包括家庭功能和父母的心理健康水平.     

Genetic and environmental influences on frontal EEG asymmetry: a twin study

Research suggests that frontal EEG asymmetry (FA) is a relatively stable trait associated with individual differences in dispositional affect (affective style) and liability to mood disorders. If FA is genetically determined, it can potentially serve as an endophenotype in genetic studies of temperament and mood disorders. The purpose of this study was to assess heritability of FA as well as alpha band EEG power measured at different frontal recording sites. Resting EEG data from a population-based sample of 246 young adult female twins including 73 monozygotic (MZ) and 50 dizygotic (DZ) pairs were analyzed using linear structural equation modeling. FA measured at mid-frontal locations (F3 and F4) showed low but significant heritability, suggesting that 27% of the observed variance can be accounted for by genetic factors. There was no evidence for genetic influences on FA measured at lateral-frontal (F7 and F8) locations. In contrast, alpha band power was highly heritable at all four frontal sites (85-87%). These findings suggest that: (1) genetic influences on FA are very modest and therefore FA has a limited utility as an endophenotype for genetic studies of mood disorders and (2) prefrontal neural circuitry underlying individual differences in affective style is characterized by high developmental plasticity.     

Genetic and environmental influences on emotion-modulated startle reflex: a twin study

Emotion-modulated startle reflex is an important indicator of traitlike differences in affective processing implicated in the biological basis of personality and psychopathology. This study examined heritability of startle modulation by affective pictures in 66 pairs of monozygotic and 57 pairs of dizygotic female twins. Consistent with previous studies, startle magnitude was significantly influenced by emotional valence of the picture (positive < neutral < negative). Absolute response magnitude showed high heritability in all three valence conditions (59-61%); however, there were no significant genetic influences on the amount of startle modulation. Thus, our data do not support the hypothesis that emotion-modulated startle can serve as an indicator of genetically transmitted individual differences in affective processing.     

Genetic and environmental influences on coping styles: a twin study.

OBJECTIVE: Coping styles are generally considered to be environmentally driven, primarily by family influences. However, because personality traits are commonly influenced by genetic effects, we hypothesized that heredity is also important for coping. METHODS: We tested this hypothesis by assessing 19 coping styles, as well as four secondary coping factors, by questionnaire in 212 pairs of monozygotic and dizygotic twins. We then examined heredity by structural equation modeling. RESULTS: All coping styles showed evidence of genetic influences. The coping styles shared one common genetic factor. In addition, each coping style was also influenced by other separate genetic factors. Shared environment had no significant influence on coping styles. Three of 19 more specific coping styles showed shared environmental effects as well as genetic influences, 14 were solely under genetic influences, and two showed only shared environment effects. CONCLUSIONS: We suggest that hereditary effects on certain coping style preferences cannot be explained solely by genetic influences on major personality traits and temperament. An analysis of the relationships between coping and personality in twin subjects may elucidate the distinction between genetic and environmental effects.     

A twin study of aryl hydrocarbon hydroxylase (AHH) inducibility in cultured lymphocytes

Aryl hydrocarbon hydroxylase (AHH) inducibility was studied in cultured lymphocytes from 28 monozygotic (MZ) and 19 dizygotic (DZ) twin pairs. The results indicate that the induced level of AHH activity as well as inducibility (expressed as the ratio between levels in induced and non-induced cells) are inherited. The best (h²) estimate of heritability is 0.7. There was no suggestion that non-induced AHH activity level is an inherited trait. Inducibility of AHH was not normally distributed and the distribution observed in this limited series might even be trimodal. The results of the study appear to confirm previous reports that AHH inducibility is an inherited trait, and do not exclude the possibility that the major part of the variation is controlled by one locus.     

No genetic effect on variation in field dependence: A study of rod-and-frame scores in families of monozygotic twins

Rod-and-frame scores for 74 monozygotic (MZ) twin pairs and their spouses and children were analyzed, applying the MZ half-sib model [Nance, W. E., and Corey L. A., (1976). Genetics83:811–826] to estimate the relative importance of genetic and environmental effects. The results indicated no genetic effect and a large individual environmental effect (69% of the total variance). The environmental variance shared by the nuclear family members was 31% of the total variance. Of this common component, approximately two-thirds was shared by the members of the two families of cotwins, suggesting that families of monozygotic twins share many experiences or possibly influence each other reciprocally.The Norwegian Research Council for Science and Humanities provided financial support     

Human neuroscience at National Institute on Drug Abuse: Implications for genetics research

It is becoming clear that there is a genetic component to drug abuse. Family studies, adoption studies, and critical twin studies have all pointed to some genetic vulnerability or risk factors for an individual to abuse psychoactive drugs depending on certain psychopathologies in the biological parents and/or parents' own drug use. The question for the next generation of research at the National Institute on Drug Abuse (NIDA) is to apply the rapidly developing technology in molecular genetics in an effort to determine the candidate genes contributing to the risk. © 1994 Wiley-Liss, Inc.