Originally published on October 16, 2017.

The question: Why does divorce run in families?

It is known that children of divorced parents are more likely to experience the failure of their own marriage later in life.

Researchers, including Dr. Jessica Salvatore, an assistant professor in the department of psychology at Virginia Commonwealth University in Richmond set out to answer the question "Why does divorce run in families?" Previous studies have suggested that divorce is transmitted across generations psychologically — if you witness your parents struggle in their marriage, you may internalize that behaviour then replicate in your own relationship.

Dr. Salvatore decided to investigate divorce's genetic roots in a paper for the journal Psychological Science, which was published in January.

Bob McDonald: If divorce really does run in families, but not for the reasons we think, is there in fact a divorce gene?

Dr. Jessica Salvatore: We do know that divorce is what we call a heritable trait, meaning that genes influence it. However we don't necessarily know what specific genes or genetic variants contribute to that heritability. So no, there is no one locus in your genome that would tell you whether or not you're going to get divorced.

BM: So then what kind of genetics are we talking about?

JS: We looked at inferred genotypes. The same sets of genes that contribute to divorce also are involved in personality traits that are related to divorce. Something like neuroticism, that's someone's proneness to negative affective states, things like anxiety and worry. And we know from more clinical, laboratory-based studies of couples, that when someone is high in neuroticism, they tend to see their partner's behaviour as more negative than an objective observer views that same type of behaviour.

This can really lead to a pernicious or damaging cycle within a relationship, because that can be hard to please a partner when everything you do is disappointing. So these types of personality-driven cognitive distortions, I think, make a really high potential target for therapeutic intervention for distressed couples.

BM: Well, tell me about your study that showed this relationship between genetics and divorce across generations.

JS: We studied this question in the context of an adoption design. Adoption design is really useful for helping to tease apart the degree to which genes versus the environment contribute to an outcome. That's because what we're looking at in an adoption study is whether the adoptees resemble either their biological parents, who contribute genes, or their adoptive parents, who contribute the rearing environment.

We were able to look at the resemblance between adoptees and their biological parents' histories of divorce, and adoptees and their adoptive parents histories of divorce. This was a massive sample size for this type of study. We were looking at about 20,000 individuals who had been adopted. They were placed up for adoption almost immediately after they were born, so they didn't experience the dissolution of their biological parents' marriage.

What we found was that the adoptees tended to resemble their biological parents who contributed genes to the adoptees, and not their adoptive parents who contributed the rearing environment.

So from this pattern of facts we infer that it is genes that contribute to the transmission of divorce from parents to children as opposed to the rearing environment.

BM: I think what most of us would think about with divorce is the reason it would run in families is that the children just saw their parents go through a really rough time so it's more of an environmental thing. You're saying you were able to separate those two?

JS: Exactly. The interpretation from these other studies, and the evidence coming out of these other studies, would suggest that there's something sort of psychologically damaging about watching your parents go through a divorce, that undermines your ability to stick with it when the going gets tough in your own marriage later on. But the confounding factor that these previous studies haven't really addressed is that divorcing parents not only are giving a "divorced environment" to their children; they're also contributing genes to their offspring.

BM: If genetics plays a role in divorce, how does that fit into the other factors? Because clearly there has to be some environmental impact there.

JS: Absolutely. Our study certainly does not imply that it's only genes that matter for divorce. In fact we know that that can't possibly be true because divorce is something that happens between two people. So there is a super-important part of your environment, and that is who your partner is and how your own traits and liabilities and strengths come together in the context of that relationship.

Our study by no means suggests that genes are the only thing responsible for divorce. It's just part of the picture and appears to be the primary explanation for why divorce runs from parents to children.

BM: You mentioned that your database involved around 20,000 children of divorced parents. So how many of those went on to divorce themselves?

JS: Of our sample of 20,000 adoptees, of those who got married, about 46 per cent of them went on to experience a divorce in their own relationship.

BM: Wow. 46 per cent.

JS: It's funny, everyone seems surprised by that, but that's about the going rate in most western countries these days.

BM: When it comes to genetics, you can avoid being tall or having blue eyes that you got from your parents, but can you avoid the negative impact of genetic personality traits that your parents may have given you?

JS: Yeah. Just because something is genetically influenced doesn't mean that it isn't modifiable. If someone knows what their liabilities are, certainly those things are amenable to being changed, they're open to environmental influence.

Q&A edited for length and clarity.