Studies have shown that the phenotype of nonhuman animals can be shaped by the genomes of surrounding individuals, but whether humans experience similar effects is unclear.
To determine whether being surrounded by peers with a genetic predisposition to smoke affects an individual’s smoking behavior, researchers analyzed survey data collected between 1994 and 1995 from 3,895 middle school and high school students in the United States. Additionally, between 2008 and 2009, DNA samples were collected from the students.
The genetic propensity to smoke in grade-mates and friends was each positively associated with an individual’s smoking behavior, although the correlation was stronger for individuals and their grade-mates.
The authors also found that sharing a grade with even a small minority of peers who had a high genetic propensity to smoke greatly increased an individuals’ tendency to smoke. However, having peers with low genetic propensity to smoke did not reduce grade-mates’ tendency to smoke.
The findings suggest that grade-mate smoking behavior may be a stronger predictor of individual smoking behavior than the individual’s own genetic propensity. Moreover, genes should be treated as an important part of an individual’s social environment, and social environments should be considered in the context of genetic influence, according to the authors.
Smoking and peers' genetic risk
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