Gene-environment correlation

Gene-environment correlation (or genotype-environment correlation) is said to occur when exposure to environmental conditions depends on an individual's genotype.

Gene-environment correlations (or rGE) is correlation of two traits, e.g. height and weight, which would mean that when one changes, so does the other. Gene-environment correlations can arise by both causal and non-causal mechanisms. Of principal interest are those causal mechanisms which indicate genetic control over environmental exposure. Genetic variants influence environmental exposure indirectly via behavior. Three causal mechanisms giving rise to gene-environment correlations have been described.

Gene-environment correlation can also arise from non-causal mechanisms, including evolutionary processes and behavioral 'contamination' of the environmental measure. Evolutionary processes, such as genetic drift and natural selection, can cause allele frequencies to differ between populations. For example, exposure to malaria-bearing mosquitoes over many generations may have caused the higher allele frequency among certain ethnic groups for the sickle hemoglobin (HbS) allele, a recessive mutation that causes sickle-cell disease but confers resistance against malaria. In this way, HbS genotype has become associated with the malarial environment.

Twin and adoption studies have provided much of the evidence for gene-environment correlations by demonstrating that putative environmental measures are heritable. For example, studies of adult twins have shown that desirable and undesirable life events are moderately heritable as are specific life events and life circumstances, including divorce, the propensity to marry, marital quality and social support. Studies in which researchers have measured child-specific aspects of the environment have also shown that putative environmental factors, such as parental discipline or warmth, are moderately heritable. Television viewing, peer group orientations and social attitudes have all been shown to be moderately heritable. There is also a growing literature on the genetic factors influencing behaviors that constitute a risk to health, such as the consumption of alcohol, tobacco and illegal drugs, and risk-taking behaviors. Like parental discipline, these health related behaviors are genetically influenced, but are thought to have environmentally mediated effects on disease. To the extent that researchers have attempted to determine why genes and environments are correlated, most evidence has pointed to the intervening effects of personality and behavioral characteristics.

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