Genes, brain and cognition.
Explore the source record for details and available documents.
Body Patterning↗
Biomedical subjects
R Plomin
Publications and source records attributed to R Plomin.
A genetic analysis of weight and overweight in 4-year-old twin pairs.
OBJECTIVE: Although many twin and adoption studies document genetic influence on individual differences in weight, much less is known about genetic influences on overweight, about the genetic links between weight and overweight, or about the origins of weight and overweight in childhood, an age that might provide a good target for prevention of obesity. We tested the hypothesis that, in early childhood, overweight is as heritable as weight and that weight and overweight are linked genetically. DESIGN: Model-fitting analyses were used to compare monozygotic (MZ) and dizygotic (DZ) twins (same-sex and opposite-sex) for weight and overweight. SUBJECTS: The sample included 3636 4-y-old twins born in the UK in 1994. MEASUREMENTS: Heights and weights reported by parents were used to assess weight corrected for height, which yields results similar to body mass index (BMI) but corrects more completely for genetic effects on height. RESULTS: At 4 y of age, genetic factors contributed substantially both to individual differences in weight throughout the distribution and to the mean weight difference between overweight children and the rest of the population. Unlike results later in life, weight and overweight in 4-y-olds also suggest substantial shared family environmental influence. Results are similar for boys and girls. CONCLUSIONS: Overweight is the quantitative extreme of genetic and environmental factors responsible for normal variation in weight in childhood. Genes associated with overweight are likely to be associated with variation in weight throughout the distribution, as assumed by quantitative trait locus (QTL) theory. These findings linking weight and overweight in childhood have far-reaching implications for molecular genetic attempts to identify specific genes responsible for genetic influence, for investigating pathways between genes and behaviour, and for intervention and prevention.
Body Height↗
Food and activity preferences in children of lean and obese parents.
BACKGROUND: Children of obese parents have a substantially higher risk of adult obesity than children of lean parents. Adoption and twin studies have shown that this risk is largely genetic but the proximal mechanisms of the genetic risk are not known. Comparisons of energy intake or expenditure in children of obese and lean parents have produced mixed, but generally negative results. An alternative hypothesis is that the early expression of obesity risk is through food and activity preferences, which provides a basis for later weight gain. The aim of this study was therefore to compare food and activity preferences in a large sample of young children from obese and lean families using parental obesity as a marker of the obesity-risk phenotype. Because the children from the families with obese parents were not yet overweight, differences observed in the two types of families are more likely to be causes than effects of obesity. METHODS: A total of 428 children aged 4-5 y, whose parents were either obese/overweight or normal-weight/lean were selected from a population sample of families with twin births. Food and activity preferences were assessed with a combination of food intake and taste tasks, and questionnaires completed by the mother during a home visit. FINDINGS: Children from the obese/overweight families had a higher preference for fatty foods in a taste test, a lower liking for vegetables, and a more 'overeating-type' eating style. They also had a stronger preference for sedentary activities, and spent more time in sedentary pastimes. There were no differences in speed of eating or reported frequency of intake of high-fat foods. CONCLUSION: Part of the process whereby a genetic risk of obesity is transmitted to the next generation could be through differences in diet and activity preferences, which would place susceptible individuals at risk of positive energy balance in the permissive nutritional environment of industrialised countries today.
Child, Preschool↗
Hyperactivity in preschool children is highly heritable.
Explore the source record for details and available documents.
Attention Deficit Disorder with Hyperactivity↗
Genes and environment in asthma: a study of 4 year old twins.
BACKGROUND: Although the genetic and environmental factors of asthma have been investigated in adolescence and adulthood, no previous studies have focused on the early development of asthma. AIMS: To test, in a large sample of 4 year old twins, the hypotheses derived from the literature on adolescents and adults that genetic influences are substantial and shared environmental influences are modest. METHODS: The sample consisted of 4910 twin pairs who were born in England and Wales in 1994 and 1995. Data on asthma status were obtained from the twins' parents by postal questionnaire. RESULTS: Univariate parameter estimates derived from model fitting were 68% heritability, 13% shared environment, and 19% non-shared environment. CONCLUSIONS: Our findings suggest that asthma is highly heritable in 4 year olds, whereas shared environmental influences are not statistically significant.
Analysis of Variance↗
Why are children in the same family so different? Nonshared environment a decade later.
OBJECTIVE: To review recent developments in the study of nonshared environment; that is, the environmental influences that make children growing up in the same family different, rather than similar. METHOD: We review several recent influential books and papers on the subject of nonshared environment from the decade following the 1987 paper that highlighted its importance in psychological development. RESULTS: Modest progress has been made toward identifying the specific aspects of the environment responsible for nonshared environment. Although parents treat their multiple children differently, such differential treatment accounts for only a small amount of nonshared environmental influence, once genetic factors are controlled. It has been suggested that some degree of nonshared environment may be due to the fact that siblings react differently to ostensibly shared environmental influences. Peer influence and other experiences outside the family may be more important sources of systematic nonshared environment. CONCLUSIONS: Despite the difficulties encountered in identifying specific sources of nonshared environment, the fact remains that most environmental variance affecting the development of psychological dimensions and psychiatric disorders is not shared by children growing up in the same family. More research and theory are needed to explain why such siblings are so different. Chance, in the sense of idiosyncratic experiences, also needs to be considered.
Adoption↗
Genetics, environment and cognitive abilities: review and work in progress towards a genome scan for quantitative trait locus associations using DNA pooling.
BACKGROUND: Multivariate genetic research indicates that genetic effects on diverse cognitive abilities are general rather than specific or modular. General cognitive ability (g), a key factor in learning and memory, is among the most heritable behavioural traits. AIMS: To give a brief overview of quantitative genetic research on g and to describe initial results from a programme of research that aims to identify genes responsible for the substantial heritability of general cognitive ability. METHOD: The research uses a new technique called DNA pooling, which combines DNA from individuals within a group and makes it feasible to screen thousands of DNA markers for a systematic scan of the genome for associations between DNA markers and g. Two independent samples of children with very high g scores and two control samples of children with average g scores were compared in a systematic scan of 147 markers on chromosome 4 and 66 markers on chromosome 22. RESULTS: Three replicated associations on chromosome 4 were identified using DNA pooling and confirmed using individual genotyping. CONCLUSIONS: These first results of the application of DNA pooling in systematic analysis of allelic association are encouraging.
Adult↗
Genetic and environmental influences on social support in later life: a longitudinal analysis.
The present study assessed the etiology of individual differences in social support over a six-year period. The availability of friend support, family support, and the perceived adequacy of the social support network was assessed three times using identical and same-gender fraternal twins reared together and reared apart from the Swedish Adoption/Twin Study of Aging. Results are based on the pairwise responses at the three occasions of measurement (labeled Q1, Q2, and Q3): 462 pairs at Q1 (assessed October 1984), 474 pairs at Q2 (October 1987), and 431 pairs at Q3 (October 1990). The longitudinal phenotypic correlations (ranging from .49 to .77) indicate that social support is a moderately stable characteristic. Qualitative genetic model-fitting analyses resulted in significant heritability estimates for the social support measures at all three measurement occasions. Results also indicate considerable stability in genetic effects across measurement occasions, with genetic correlations ranging from .65 to .97. Nonshared environmental influences were substantial contributors to social support, but were less stable across the measurement occasions, with correlations ranging from .07 to .52.
Adult↗
Genetic factors contributing to learning and language delays and disabilities.
Reading disability shows substantial genetic influence, and it is in this area of early-onset cognitive delays that genetic research has made the most progress. Reading disability also provides the first success story for identifying replicable quantitative trait locus linkage for behavioral disorders. Language and communication disorders also show substantial genetic influence, as does general cognitive ability (intelligence), which plays a role in most cognitive disabilities. The genetics of reading disability, communication disorders, and mental retardation are reviewed. Early-onset cognitive disabilities are prime targets for molecular genetic studies that will eventually identify specific genes that can predict risk, assist diagnosis and treatment, and provide discrete windows through which we can investigate the development of brain mechanisms that lie between genes and behavior.
Adolescent↗
Genetic and gender influences on nocturnal bladder control--a study of 2900 3-year-old twin pairs.
OBJECTIVE: The present study of over 2900 twin pairs born in England and Wales in 1994 examines the influences of genetics and gender on nocturnal bladder control at 3 years of age. MATERIALS AND METHOD: Parent report data was analysed in terms of means and components of variance, using a sex-limitation model to explore genetic and environmental variation within and between the sexes. RESULTS: Both genetics and gender are seen to influence acquisition: bladder control at 3 years is moderately heritable (24%), and girls show on average slightly increased acquisition compared with boys, even within opposite-sex pairs. The sex-limitation modelling showed an interaction between genetic influence and gender whereby nocturnal bladder control was significantly more heritable in boys (33%) than girls (10%). CONCLUSIONS: Both genetics and gender are important and interacting factors in the aetiology of nocturnal bladder control.
Child, Preschool↗
Polymorphisms of genes controlling homocysteine/folate metabolism and cognitive function.
Elevated concentrations of the amino acid homocysteine and/or folate deficiency have been reported to affect neural development/function in both human patients and animal models. We have investigated the distribution of functional polymorphisms in genes involved in homocysteine/folate metabolism in children with high IQ and in children with average IQ. No differences in the frequencies of genetic variants in the methionine synthase or methylenetetrahydrofolate reductase genes were found. However, the cystathionine beta-synthase (CBS) 844ins68 allele was significantly underrepresented in children with high IQ. The mechanism by which a functional genetic variant in the CBS gene may influence cognitive function remains to be determined.
Adolescent↗
Chasing behaviour genes into the next millennium.
Both linkage and association strategies are appropriate for the characterization of genes implicated in human behavioural dimensions and disorders. For the foreseeable future, association studies involving whole-genome scanning will combine strategies using both single-nucleotide and simple-sequence-repeat polymorphisms.
Genetic Linkage↗
Lexical and grammatical development: a behavioural genetic perspective.
The relation of lexical and grammatical knowledge is at the core of many controversies in linguistics and psycholinguistics. Recent empirical findings that the two are highly correlated in early language development have further energized the theoretical debate. Behavioural genetics provides an illuminating new tool to explore this question, by addressing the question of whether the empirical correlation simply reflects the fact that environments which facilitate one aspect of language growth also facilitate the other, or whether the same underlying acquisition mechanisms, influenced by the same genes, are responsible for the correlation. We explored this issue in a study of 2898 pairs of two-year-old twins born in England and Wales. Language development was assessed by their parents using an adapted version of the MacArthur Communicative Development Inventory which assesses vocabulary and grammar. Moderate heritabilities were found for both. As in previous studies, measures of vocabulary and sentence complexity were substantially correlated (r = 0.66). Behaviour-genetic modelling of the relation of vocabulary and grammar produced an estimated value of 0.61 for the genetic correlation, a measure of the overlap of the genetic effects that contribute to the two aspects of language development. In contrast, a measure of nonverbal cognitive development, the PARCA, was only weakly correlated at both the phenotypic level and at the level of genetic correlations with the language measures. Thus, although the distinction between verbal and nonverbal skills has a genetic basis underlying the phenotypic dissociation, there is little evidence either genetically or phenotypically for a dissociation between vocabulary and grammar within language.
Child Language↗
The interaction of prematurity with genetic and environmental influences on cognitive development in twins.
OBJECTIVE: To investigate how the degree of prematurity interacts with genetic and environmental influences in their effect on verbal and nonverbal cognitive development. STUDY DESIGN: The target sample consisted of more than 2000 pairs of twins born in England and Wales in 1994. At 24 months, measures of verbal and non-verbal cognitive development were obtained from the twins' parents. The sample was divided into 3 groups according to degree of prematurity: very preterm or high-risk (<32 weeks), moderately preterm or medium-risk (32-33 weeks), and mildly preterm/term or low-risk (>34 weeks). Quantitative genetic analyses were used to assess the contributions of genetic and environmental influences on vocabulary and cognitive development. RESULTS: The results indicated gene-environment interactions. For the high-risk group, genetic effects on both verbal and non-verbal cognitive ability were completely overshadowed by shared environmental factors, whereas for both medium- and low-risk groups, additive genetic effects explained 18% to 33% of the variance. CONCLUSIONS: Our findings indicate that genetic factors are not responsible for cognitive outcomes of very preterm infants and suggest that early environmental influences appear to affect verbal and non-verbal cognitive development at 2 years of age.
Child Development↗
Neighborhood deprivation affects children's mental health: environmental risks identified in a genetic design.
The possibility that neighborhood conditions affect children's development has captured much attention because of its implications for prevention. But does growing up in deprived neighborhoods matter above and beyond a genetic liability to behavior problems, if genetically vulnerable families tend to concentrate in poor neighborhoods? A nationwide study of 2-year-old twins shows that children in deprived neighborhoods were at increased risk for emotional and behavioral problems over and above any genetic liability. Environmental factors shared by members of a family accounted for 20% of the population variation in children's behavior problems, and neighborhood deprivation accounted for 5% of this family-wide environmental effect. The results suggest that the link between poor neighborhoods and children's mental health may be a true environmental effect, and demonstrate that genetic designs are environmentally informative and can be used to identify modifiable risk factors for promoting child health.
Affective Symptoms↗
Parent ratings of temperament in twins: explaining the 'too low' DZ correlations.
Twin studies of child temperament using objective measures consistently suggest moderate heritability for most dimensions. However, parent rating measures produce unusual patterns of results. Intraclass correlations for identical (MZ) twins are typically high, whereas fraternal (DZ) twin intraclass correlations are much lower than would be predicted from an additive genetic model. The 'too low' DZ correlations can be explained by parent-rating biases that either exaggerate the differences between DZ twins (contrast effects) or that inflate the similarity of MZ twins (assimilation effects), or by the presence of non-additive genetic variance. To evaluate the three possible explanations, we used model-fitting procedures applied to parent-rating data averaged across 14, 20, 24, and 36 months of age in a sample of 196 twin pairs participating in the MacArthur Longitudinal Twin Study. The data were best described by a model that included contrast effects. Implications for non-twin research are discussed.
Analysis of Variance↗
GENESiS: creating a composite index of the vulnerability to anxiety and depression in a community-based sample of siblings.
There is considerable evidence for a unitary and dimensional view of the genetic vulnerability to symptoms of anxiety and depression. The GENESiS (Genetic Environmental-Nature of Emotional States in Siblings) Study aims to use a multivariate approach to detect genetic loci that contribute to individual differences in this vulnerability dimension. The study used the UK General Practice Research Framework to generate a community-based sample of siblings. Questionnaire measures of anxiety/depression included the short form of the neuroticism scale from the revised Eysenck Personality Questionnaire (EPQ-N), the General Health Questionnaire (GHQ-12), and the anxious arousal and high positive affect subscales from the Mood and Anxiety Symptoms Questionnaire (MASQ-AA and MASQ-HPA). Genetic model-fitting of 2658 unselected sibships provided evidence for a single common genetic (familial) factor that accounted for a substantial proportion of the genetic variances and covariances of these four measures. Using the parameter estimates of this model, we constructed a composite index of this common genetic factor. This index, which has a sib correlation of 0.22, will be used as a quantitative phenotype in the molecular genetic phase of GENESiS.
Adult↗
Infant zygosity can be assigned by parental report questionnaire data.
A parental report questionnaire posted to a population sample of 18-month-old twins correctly assigned zygosity in 95%of cases when validated against zygosity determined by identity of polymorphic DNA markers. The questionnaire was as accurate when readministered at 3 years of age, with 96% of children being assigned the same zygosity on both occasions. The results validate the use of parental report questionnaire data to determine zygosity in infancy.
Chi-Square Distribution↗