Quantitative genetics in the era of molecular genetics: learning abilities and disabilities as an example.
OBJECTIVE
To consider recent findings from quantitative genetic research in the context of molecular genetic research, especially genome-wide association studies. We focus on findings that go beyond merely estimating heritability. We use learning abilities and disabilities as examples.


METHODS
Recent twin research in the area of learning abilities and disabilities was reviewed.


RESULTS
Three findings from quantitative genetic research stand out for their far-reaching implications for child and adolescent psychiatry. First, common disorders such as learning difficulties are the quantitative extreme of the same genetic factors responsible for genetic influence throughout the normal distribution (the Common Disorders are Quantitative Traits Hypothesis). Second, the same set of genes is largely responsible for genetic influence across diverse learning and cognitive abilities and disabilities (the Generalist Genes Hypothesis). Third, experiences are just as influenced genetically as are behaviors and genetic factors mediate associations between widely used measures of the environment and behavioural outcomes (the Nature of Nurture Hypothesis).


CONCLUSIONS
Quantitative genetics can go far beyond the rudimentary "how much" question about nature versus nurture, and can continue to provide important findings in the era of molecular genetics.
Haworth
Claire M A
CM
Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry, King's College London, United Kingdom. Claire.Haworth@iop.kcl.ac.uk
Plomin
Robert
R
D000293:Adolescent; D002648:Child; D003072:Cognition Disorders / Q000175:diagnosis / Q000235:genetics* / Q000523:psychology; D044127:Epigenesis, Genetic / Q000235:genetics; D005544:Forecasting; D020022:Genetic Predisposition to Disease / Q000235:genetics / Q000523:psychology; D055106:Genome-Wide Association Study; D006801:Humans; D007859:Learning Disabilities / Q000175:diagnosis / Q000235:genetics* / Q000523:psychology; D008967:Molecular Biology / Q000639:trends; D019655:Quantitative Trait, Heritable; D012931:Social Environment