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Your sweetheart’s genes will affect your life, too

February 12, 2021

Couple dating

They say that biology is destiny. New research doubles down on that notion, suggesting that some of your traits may be affected by the genes … of your partner.  Well, happy Valentine’s Day!

Researchers at the University of Edinburgh recently concluded that in around 25% of 105 complex traits they considered in more than 80,000 heterosexual couples, “partner heritability is consistent with the existence of indirect genetic effects including a wide variety of traits such as dietary traits, mental health and disease,” as they wrote in Nature Human Behavior.

By indirect genetic effects, the researchers mean the genes of one individual affect the phenotype (observable characteristics, including behavior) of other individuals. The Scientist offered a simple hypothetical example of such effects: A person who is genetically predisposed to smoking might raise their partner’s risk of lung cancer by exposing them to cigarette smoke or encouraging them to smoke more.

“This shows that the environment linked to complex traits is partially explained by the genotype of other individuals and motivates the need to find new ways of studying the environment,” the researchers wrote.

Biobank data analyzed

To arrive at their conclusions, the researchers used data about the couples’ genes, health and lifestyle habits from the UK Biobank using a statistical model to find associations between individuals’ traits and their partner’s DNA. The researchers “concluded that around 25 percent of the associations did indeed involve at least some causation—that is, one person’s genotype was having a detectable effect on another person’s phenotype,” The Scientist wrote, citing beef intake, TV watching time, and susceptibility to mood swings among examples. Researchers tried to weed out effects of “assortative mating,” such as a tall person opting for a tallish mate for reasons other than indirect genetic effects.

Researchers acknowledge the value of going deeper in future research by, for instance, studying the same people over many years. A researcher who wasn’t involved in the study, Daniel Belsky, an epidemiologist at Columbia University Mailman School of Public Health, noted that the work undermines the fatalistic assumption that one’s own genes determine one’s life.

“Observations like this . . . illustrate ways in which a wide range of environments—in this case, another person you’ve chosen to share your life with—intercede between the genetic risk a person is born with and the health outcome that we’re interested in protecting them from. This is another argument against a deterministic interpretation of a person’s genetic background, when you think about the kind of life that they’re going to lead and the sort of health risks they’re going to have.”

At the same time, it’s one more argument for choosing your mate wisely.