Gene-environment correlation: difficulties and a natural experiment-based strategy.
OBJECTIVE
We explored how gene-environment correlations can result in endogenous models, how natural experiments can protect against this threat, and if unbiased estimates from natural experiments are generalizable to other contexts.


METHODS
We compared a natural experiment, the College Roommate Study, which measured genes and behaviors of college students and their randomly assigned roommates in a southern public university, with observational data from the National Longitudinal Study of Adolescent Health in 2008. We predicted exposure to exercising peers using genetic markers and estimated environmental effects on alcohol consumption. A mixed-linear model estimated an alcohol consumption variance that was attributable to genetic markers and across peer environments.


RESULTS
Peer exercise environment was associated with respondent genotype in observational data, but not in the natural experiment. The effects of peer drinking and presence of a general gene-environment interaction were similar between data sets.


CONCLUSIONS
Natural experiments, like random roommate assignment, could protect against potential bias introduced by gene-environment correlations. When combined with representative observational data, unbiased and generalizable causal effects could be estimated.
At the time of the study, Brandon Wagner, Hexuan Liu, and Guang Guo were with the Department of Sociology and Carolina Population Center, University of North Carolina, Chapel Hill. Guang Guo is also with the Carolina Center for Genome Sciences, University of North Carolina, Chapel Hill. Jiang Li is with Department of Health Behavior, Gillings School of Global Public Health, University of North Carolina, Chapel Hill.
Brandon
B
Wagner
Jiang
J
Li
Hexuan
H
Liu
Guang
G
Guo
D000293:Adolescent; D000428:Alcohol Drinking / Q000453:epidemiology / Q000235:genetics*; D035843:Biomedical Research / Q000379:methods*; D015444:Exercise / Q000502:physiology*; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008954:Models, Biological; D019370:Observation; D010379:Peer Group; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012107:Research Design; D013334:Students; D014495:Universities