Biomedical subjects

Robert Plomin

Publications and source records attributed to Robert Plomin.

At least 37 records · Page 2Linked to original sources

PubMed2005

Continuity and change in preschool ADHD symptoms: longitudinal genetic analysis with contrast effects.

The genetic and environmental mediation of continuity and change in parent-reported ADHD symptoms were investigated in a cohort of over 6000 twin pairs at 2, 3 and 4 years of age. Genetic analyses of the cross-sectional data yielded heritability estimates of 0.78-0.81 at each age, with contrast effects. A common pathway model provided the best fit to the longitudinal data, indicating that genetic influences underlie 91% of the stable variance in ADHD symptomatology. In other words, what is stable for ADHD symptoms is largely genetic. Contrast effects acting in the same direction at different ages contributed to the observed continuity:longitudinal correlations were greater for dizygotic than monozygotic twins.

Attention Deficit Disorder with Hyperactivity↗

PubMed2005

Assessing reliability, heritability and general cognitive ability in a battery of cognitive tasks for laboratory mice.

This report includes the first sibling study of mouse behavior, and presents evidence for a heritable general cognitive ability (g) factor influencing cognitive batteries. Data from a population of male and female outbred mice (n = 84), and a replication study of male sibling pairs (n = 167) are reported. Arenas employed were the T-maze, the Morris water maze, the puzzle box, the Hebb-Williams maze, object exploration, a water plus-maze, and a second food-puzzle arena. The results show a factor structure consistent with the presence of g in mice. Employing one score per arena, this factor accounts for 41% of the variance in the first study (or 36% after sex regression) and 23% in the second, where this factor also showed sibling correlations of 0.17-0.21, which translates into an upper-limit heritability estimate of around 40%. Reliabilities of many tasks are low and consequently set an even lower ceiling for inter-arena or sibling correlations. Nevertheless, the factor structure is seen to remain fairly robust across permutations of the battery composition and the current findings fit well with other recent studies.

Animals↗

PubMed2005

The etiology of behavior problems in 7-year-old twins: substantial genetic influence and negligible shared environmental influence for parent ratings and ratings by same and different teachers.

Parent ratings of behavior problems in childhood show substantial genetic influence and modest shared environmental influence. However, few studies have compared these results to teacher ratings and no previous studies have compared same-teacher ratings to different-teacher ratings. 3,714 7-year-old twin pairs in the Twins Early Development Study were rated by parents and teachers on the Strengths and Difficulties Questionnaire. Substantial heritability and negligible shared environmental influence were found for data from all three raters for total behavior problems, hyperactivity, prosocial behavior, peer problems, conduct problems, and emotional symptoms. Sex-limitation models revealed similar results for males and females, although there was some evidence for greater heritability for boys, especially when twins were rated by the same teacher.

Attention Deficit Disorder with Hyperactivity↗

PubMed2005

Masculine girls and feminine boys: genetic and environmental contributions to atypical gender development in early childhood.

In this genetic study of atypical gender role development, parents of 5,799 twin pairs, ages 3 and 4, rated their twin children's masculinity and femininity. Boys were selected as gender atypical if they were highly feminine (top 5%, 10%, or 15%) relative to other boys, and girls were selected if they were highly masculine relative to other girls. Gender-atypical boys and girls were each divided into 2 groups: fully gender atypical (e.g., feminine boys also low on masculinity) and partially gender atypical (e.g., feminine boys who are not low on masculinity). DeFries-Fulker (DF; J. C. DeFries & D. W. Fulker, 1985, 1988) extremes analysis yielded moderate group heritability and substantial shared environment effects for atypical gender role behavior. However, for fully gender-atypical girls, group heritability accounted for most of the variance, and shared environment had no effect. The results are discussed in light of past studies and potential implications for atypical gender development.

Child, Preschool↗

PubMed2005

Generalist genes and learning disabilities.

The authors reviewed recent quantitative genetic research on learning disabilities that led to the conclusion that genetic diagnoses differ from traditional diagnoses in that the effects of relevant genes are largely general rather than specific. This research suggests that most genes associated with common learning disabilities--language impairment, reading disability, and mathematics disability--are generalists in 3 ways. First, genes that affect common learning disabilities are largely the same genes responsible for normal variation in learning abilities. Second, genes that affect any aspect of a learning disability affect other aspects of the disability. Third, genes that affect one learning disability are also likely to affect other learning disabilities. These quantitative genetic findings have far-reaching implications for molecular genetics and neuroscience as well as psychology.

Humans↗

PubMed2005

Low expressive vocabulary: higher heritability as a function of more severe cases.

This study of 4,274 pairs of 4-year-old twins from the Twins Early Development Study explored the magnitude of genetic and environmental effects on low expressive vocabulary skill, both as a function of general cognitive ability and as a function of the severity of expressive vocabulary impairment. Assessments were conducted through parent report measures. Two types of vocabulary deficit were identified: low vocabulary paired with typical general cognition (i.e., specific expressive vocabulary impairment) and low vocabulary paired with low general cognition (i.e., nonspecific expressive vocabulary impairment). The magnitude of genetic and environmental effects on low expressive vocabulary skill did not differ for these 2 types of expressive vocabulary deficit. By systematically varying the cutoffs used to define vocabulary and general cognitive delay, potential changes in the magnitude of genetic and environmental effects were examined. Results suggested that the severity of vocabulary deficit rather than level of cognitive functioning was a more meaningful etiological distinction: The heritability of low expressive vocabulary was higher and the influence of shared environment lower, as increasingly severe vocabulary deficits were identified. Implications for molecular genetics and the construct of specific language deficits are discussed.

Child, Preschool↗

PubMed2005

The genetic relationship between individual differences in social and nonsocial behaviours characteristic of autism.

Two types of behaviours shown in children - those reflecting social impairment and nonsocial obsessive repetitive behaviours - are central to defining and diagnosing autism spectrum disorders (ASDs). Parent and teacher data on social and nonsocial behaviours were obtained from a community sample of >3000 7-year-old twin pairs. Social and nonsocial behaviours were only modestly correlated, and it was found that some individuals had extreme scores on either social or nonsocial scales but not both. Genetic model-fitting showed that social and nonsocial behaviours are both highly heritable, but their genetic overlap is modest, with most of the genetic influence being specific to either social or nonsocial behaviours. Considering these behaviours separately might help clarify gene-brain-behaviour pathways in future research.

Autistic Disorder↗

PubMed2005

Predicting literacy at age 7 from preliteracy at age 4.

Early literacy experience and preliteracy knowledge have been shown to predict later literacy outcomes. Using a representative sample of 3,052 same-sex twin pairs (6,104 children) in the United Kingdom, we explored phenotypic and etiological interrelationships among early literacy experience, preliteracy knowledge, and school-based literacy outcomes (reading and writing). Both literacy experience and preliteracy knowledge at age 4 significantly and independently predicted literacy at age 7. Both measures also showed genetic influence that significantly predicted literacy at age 7, although genetic mediation was stronger for preliteracy knowledge than for early literacy experience. However, for both measures, shared environmental factors explained most of the association with literacy at age 7.

Age Factors↗

PubMed2005

Genetic influences on early word recognition abilities and disabilities: a study of 7-year-old twins.

BACKGROUND: A fundamental issue for child psychology concerns the origins of individual differences in early reading development. METHOD: A measure of word recognition, the Test of Word Reading Efficiency (TOWRE), was administered by telephone to a representative population sample of 3,909 same-sex and opposite-sex pairs of 7-year-old twins. Analyses allowing for sex differences in aetiology were used to estimate the extent to which genetic and environmental influences contribute to normal variation in word recognition and word recognition difficulties, defined by scores below the 5th and 10th percentiles of the unselected sample. RESULTS: Both normal variation in word recognition and impaired word recognition abilities were substantially heritable (h2 = .65-.67; h(g)2 = .37-.72). Environmental influences were primarily shared between twins, rather than specific to each individual, and small to moderate in magnitude. There was evidence for qualitative sex differences. Quantitative sex differences were also suggested at the extremes, with genetic influences being more important as a cause of reading difficulties in boys than in girls. CONCLUSIONS: These findings indicate that early individual differences and impairments in word recognition are principally influenced by genetic factors and may involve partly distinct genetic or environmental effects in boys and girls. Crucially, they also provide evidence that reading impairments are linked genetically to the normal distribution. Genetic risk for early impairments in word recognition is continuous rather than discrete.

Child↗

PubMed2005

Evidence for substantial genetic risk for psychopathy in 7-year-olds.

BACKGROUND: Individuals with early warning signs of life-long psychopathy, callous-unemotional traits (CU) and high levels of antisocial behaviour (AB) can be identified in childhood. We report here the first twin study of high levels of psychopathic tendencies in young children. METHODS: At the end of the first school year, teachers provided ratings of CU and AB for 3687 twin pairs from the Twins Early Development Study (TEDS). For the analyses of extreme CU, we selected same-sex twin pairs where at least one twin scored 1.3 or more standard deviations above the mean on the CU scale (612 probands, 459 twin pairs). For the analysis of extreme AB, we selected same-sex twin pairs where at least one twin scored 1.3 or more standard deviations above the mean on AB scale (444 probands, 364 twin pairs). Furthermore, the extreme AB sample was divided into those who were also extreme on CU (children with psychopathic tendencies; 234 probands, 187 twin pairs) and those who did not score in the extreme for CU (children without psychopathic tendencies; 210 probands, 177 twin pairs). RESULTS: DeFries-Fulker extremes analysis indicated that exhibiting high levels of CU is under strong genetic influence. Furthermore, separating children with AB into those with high and low levels of CU showed striking results: AB in children with high levels of CU is under extremely strong genetic influence and no influence of shared environment, whereas AB in children with low levels of CU shows moderate genetic and shared environmental influence. CONCLUSIONS: The remarkably high heritability for CU, and for AB children with CU, suggests that molecular genetic research on antisocial behaviour should focus on the CU core of psychopathy. Our findings also raise questions for public policy on interventions for antisocial behaviour.

Antisocial Personality Disorder↗

PubMed2005

A behavioural genomic analysis of DNA markers associated with general cognitive ability in 7-year-olds.

BACKGROUND: Five DNA markers (single-nucleotide polymorphisms, SNPs) have recently been found to be associated with general cognitive ability ('g') in a sample of 7414 7-year-old twins. These children have also been studied at 2, 3, 4, and 7 years of age on measures of cognitive and language development and behaviour problems; family environment was also assessed. METHODS: We used these data to conduct a behavioural genomic analysis of the five SNPs and a composite of them ('SNP set') that explored developmental, multivariate, and genotype-environment (GE) issues. RESULTS: The 'g' SNP set identified at 7 years yielded significant associations with 'g' as early as 2 years. In multivariate analyses at 7 years, the 'g' SNP set was more strongly associated with verbal than nonverbal ability and with reading more than mathematics performance. GE correlations were found between the SNP set for 'g' at 7 years and preschool proximal measures of the family environment (chaos and discipline) rather than distal measures (maternal education and father's occupational class), suggesting evocative rather than passive GE correlation. Significant GE interactions were found for discipline, education and occupation in which the association between the SNP set and 'g' at 7 years is stronger in low-risk environments. CONCLUSIONS: Although the effect sizes of the five SNP associations are very small, behavioural genomic analyses using a 'g' SNP set illustrate how developmental, multivariate and GE questions can be addressed as more DNA associations are identified for complex traits such as 'g'.

Child↗

PubMed2005

Finding genes in child psychology and psychiatry: when are we going to be there?

BACKGROUND: The seven papers in this special section chart where we are in the quest for quantitative trait loci (QTLs) in key areas of child psychology and psychiatry such as reading and hyperactivity. But we are not there yet. METHODS: This commentary considers some new developments that are likely to accelerate the journey towards the identification of QTLs. RESULTS: The single most important factor is the need for very large samples to attain adequate power to detect and replicate QTLs of very small effect size. Another important development is the microarray, which makes it possible to genotype hundreds of thousands of SNPs simultaneously. Using microarrays in association studies allows SNPs across the whole genome to be genotyped. Microarrays will boost power even more when they contain all functional polymorphisms in the genome, including functional non-coding DNA. CONCLUSIONS: Once replicable QTLs are identified in areas such as reading and hyperactivity, the real journey will begin. Future studies will use sets of QTLs as genetic risk indicators in top-down behavioural genomic research, leading to gene-based diagnoses, gene-based treatments tailored to the individual, and early warning systems and interventions. These discoveries will eventually help to prevent or at least ameliorate childhood disorders before they cast their long shadow over development.

Child↗

PubMed2005

Single-nucleotide polymorphism genotyping in DNA pools.

To undertake partial, or complete, genome screens by association-based methodology for quantitative trait loci, multiple individuals have to be screened for large numbers of genetic markers. Consequently, much recent interest has focused on methods enabling accurate allele quantification in pooled deoxyribonucleic acid (DNA) samples. Microsatellites were the favored markers in initial studies, but the extraordinary wealth of data concerning single-nucleotide polymorphisms (SNPs) has turned attention to the quantification of SNP alleles in pools. All such approaches require accurate estimation of DNA concentrations, followed by the preparation of replicate pools, their validation, and application of procedures for determining allele frequencies. This chapter describes the important steps in preparing pools and surveys a variety of techniques that have been proposed for SNP detection. Finally, we describe the application of a generic approach using pooled DNA for detection of allele frequency differences between case and control populations based on primer extension protocols and outline a strategy for estimating SNP allele frequencies employing microarrays.

DNA↗

PubMed2004

Genome-wide linkage analysis of a composite index of neuroticism and mood-related scales in extreme selected sibships.

There is considerable evidence to suggest that the genetic vulnerabilities to depression and anxiety substantially overlap and quantitatively act to alter risk to both disorders. Continuous scales can be used to index this shared liability and are a complementary approach to the use of clinical phenotypes in the genetic analysis of depression and anxiety. The aim of this study (Genetic and Environmental Nature of Emotional States in Siblings) was to identify genetic variants for the liability to depression and anxiety after the application of quantitative genetic methodology to a large community-based sample (n = 34,371), using four well-validated questionnaires of depression and anxiety. Genetic model fitting was performed on 2658 unselected sibships, which provided evidence for a single common familial factor that accounted for a substantial proportion of the genetic variances and covariances of the four scales. Using the parameter estimates from this model, a composite index of liability (G) was constructed. This index was then used to select a smaller--but statistically powerful--sample for DNA collection (757 individuals, 297 sibships). These individuals were genotyped with more than 400 microsatellite markers. After the data were checked and cleaned, linkage analysis was performed on G and the personality scale of neuroticism using the regression-based linkage program MERLIN-REGRESS. The results indicated two potential quantitative trait loci (QTL): one on chromosome 1p (LOD 2.2) around 64 cM (43-70 cM) near marker D1S2892 and another on chromosome 6p (LOD 2.7) around 47 cM (34-63 cM) near marker D6S1610. Further exploratory sex-specific analyses suggested that these QTLs might have sex-limited effects.

Adolescent↗

PubMed2004

Verbal and nonverbal predictors of early language problems: an analysis of twins in early childhood back to infancy.

We investigated infant precursors of low language scores in early childhood. The sample included 373 probands in 130 monozygotic (MZ) and 109 same-sex dizygotic (DZ) twin pairs in which at least one member of the pair scored in the lowest 15th percentile of a control sample on a general language factor derived from tester-administered tests at 4 ; 6. From data at 2 ; 0, 3 ; 0 and 4 ; 0 the antecedents of poor language performance at 4 ; 6 for these probands were compared to 290 control children. As early as 2 ; 0, language measures substantially predicted low-language status at 4 ; 6, with predictions increasing at 3 ; 0 and 4 ; 0. Nonverbal cognitive development at 3 ; 0 and 4 ; 0 was nearly as predictive of low language at 4 ; 6 as were the language measures. Behaviour problems were also significant predictors of low language status although the associations were only about half as strong. Bivariate genetic analyses indicated that these predictions are mediated by both genetic and shared environmental links.

Child, Preschool↗

PubMed2004

Genotyping pooled DNA on microarrays: a systematic genome screen of thousands of SNPs in large samples to detect QTLs for complex traits.

Large samples and systematic screens of thousands of DNA markers are needed to detect quantitative trait loci (QTLs) of small effect size. One approach to conduct systematic genome scans for association is to use microarrays which, although expensive and non-reusable, simultaneously genotype thousands of single-nucleotide polymorphisms (SNPs). This brief report provides proof of principle that groups of pooled DNA (for example cases and controls) can be genotyped reliably on a microarray. DNA was pooled for 105 Caucasian males and genotyped three times on microarrays for more than 10,000 SNPs (Affymetrix GeneChip Mapping 10K Array Xba 131). The average correlation was 0.973 between the allele frequency estimates for the three microarrays using the same DNA pool. The correlation was 0.923 between the average of the three microarray estimates using pooled DNA and individual genotyping estimates for a Caucasian population as provided by Affymetrix (NetAffx). Thus, genotyping pooled DNA on microarrays can provide a systematic and powerful approach for identifying QTL associations for complex traits including behavioral dimensions and disorders.

DNA↗

PubMed2004

Exploring the association between anxiety and conduct problems in a large sample of twins aged 2-4.

Anxiety and conduct problems covary, yet studies have not explored the genetic and environmental origins of this association. We analyzed parent-reported anxiety and conduct problems in 6,783 pairs of twins at 2-, 3-, and 4-years of age. As anxiety and conduct problems were fairly stable across the three ages (average 1-year correlation was .53), ratings from all three were combined. The aggregate anxiety and conduct ratings correlated .33 for boys and .30 for girls. Bivariate genetic analyses indicated fairly low genetic correlations (.31 for boys, .16 for girls), and high shared environmental correlations (1.0 for boys and 0.99 for girls) between anxiety and conduct problems. Most of the phenotypic correlation was accounted for by shared environmental mediation (65% for boys and 94% for girls), indicating that many of the same family environmental factors are responsible for the development of both anxiety and conduct problems.

Anxiety↗

PubMed2004

Genetic and environmental contributions to general cognitive ability through the first 16 years of life.

The genetic and environmental contributions to the development of general cognitive ability throughout the first 16 years of life were examined using sibling data from the Colorado Adoption Project. Correlations were analyzed along with structural equation models to characterize the genetic and environmental influences on longitudinal stability and instability. Intraclass correlations reflected both considerable genetic influence at each age and modest shared environmental influence within and across ages. Modeling results suggested that genetic factors mediated phenotypic stability throughout this entire period, whereas most age-to-age instability appeared to be due to nonshared environmental influences.

Adolescent↗