Genetics influences who of us are more likely to experience a relationship breakdown, and who are more likely to remain together. But genes are not decisive, new research shows.
This text has been translated to English by the assistance of chat gpt
“Our destiny does not lie in our genes, but if a relationship were a jigsaw puzzle, our genetics would make up some of the pieces that can influence the risk of a breakup,” says sociologist Ruth Eva Jørgensen.
She recently defended her PhD at the University of Oslo (link) with the dissertation: Partnership Dissolution, Intergenerational Consequences and Partner Influence. A Socioeconomic Perspective on Family Dynamics (link).
“The findings tell us something about patterns across large population groups, not about specific individuals,” Jørgensen emphasizes.
There is no single “divorce gene” that one either has or does not have. All complex traits and life outcomes – from personality and health to relationship outcomes – are influenced by thousands of small genetic variants at the same time.
“It is the sum of these that can give some of us a slightly higher or lower risk of leaving our partner. We are talking about statistical tendencies in large samples and not a prediction of what will happen in one specific relationship,” Jørgensen clarifies.

The importance of genetics depends on environmental factors
According to the researcher, the importance of genetics will also vary across different contexts.
“The same genetic variants can have different impact depending on what kind of environment, opportunities and relationships you encounter throughout life.”
In her dissertation, Ruth Eva Jørgensen uses genetic data from the Norwegian Mother, Father and Child Cohort Study (MoBa) to examine the association between genetics and relationship breakdown in Norway.
The study is based on so-called polygenic indices, which sum up the effect of thousands of small genetic variants that influence a particular trait or outcome. Such indices can be constructed for many different traits. Based on blood samples from the couples participating in MoBa, each person in the sample has been given an index for a wide range of traits.
“We carry our genes with us from birth. They do not change with the choices we make later in life, but they can indirectly influence which choices we make. This can happen, for example, if genetics help shape personality traits, which in turn can act through the environment and the opportunities we encounter,” says Jørgensen.
To ensure that the results of the study do not simply reflect that people with a certain genetic makeup also grow up in particular families or environments, the researchers look at genetic differences between siblings, who share a family background and much of the same childhood environment.
“When genetic differences between siblings help explain differences in relationship outcomes, it strengthens the argument that genetics matter,” the sociologist explains.

Several heritable traits are linked to relationship breakdown
According to Jørgensen, our genes help make us a bit different from each other and can influence, among other things, how we handle stress, which choices we make early in life, and whom we are attracted to.
“These are the connections we are trying to understand better,” she explains.
In the study, Jørgensen and her colleagues investigate a broad set of polygenic indices and look at which of them are associated with relationship breakdown.
They find that the higher a person’s polygenic index for taking higher education, subjective wellbeing, and having a higher age at first birth, the lower their risk of relationship breakdown. People who have a higher score for risk behaviours such as smoking and early sexual debut, on the other hand, have a somewhat higher risk of relationship breakdown.
“That highly educated people separate less often than the rest of the population in Norway was something we already knew, but in this study we see that some known patterns are also reflected when we look at polygenic indices. In addition, we can examine traits that have not previously been studied,” she says.
One finding that surprised Jørgensen was that people with a higher polygenic index for neuroticism turned out to have a lower risk of relationship breakdown than others.
“One could think that neuroticism would lead to an increased risk of relationship breakdown. On the other hand, if you are somewhat more anxious and vulnerable, you may need the security a relationship provides,” says Jørgensen.

Explains nine percent of the variation among women
In one of the analyses, Jørgensen estimates how much of the variation in relationship breakdown can be attributed to common genetic variants.
“In our study I find that common genetic variants account for nine percent of the variation in women’s risk of relationship breakdown and three percent of the variation in men’s risk. Earlier twin studies have found much higher ‘heritability’, some around fifty percent.”

What explains this difference?
“Twin studies capture more or less all genetic variation, whereas the molecular-genetic methods I have used only track ‘common’ genetic variants. It takes enormous samples to detect these tiny gene variants, and not all of them can be picked up. That is why the estimated effect is lower with this method,” Jørgensen says.
In return, the molecular-genetic methods, she notes, can say something that twin studies cannot – namely which specific traits are involved, through the polygenic indices.
“We also gain information about a much larger part of the population, and not only about twin pairs,” Jørgensen explains.
She also points out that the importance of genetics will vary between contexts and generations, and especially with how strong the environmental constraints are. In periods or societies where relationship breakdown is forbidden, for example, there will be no variation for genetics to explain.
So far, this is the only study that uses these methods to study relationship breakdown.
“More similar studies in other contexts would provide greater insight into how the importance of genetics varies between societies and over time,” she says.

Until now, all the focus has been on the environment
As a sociologist, Ruth Eva Jørgensen has found it particularly interesting to study the importance of genes – and not only the environment, which is the most common focus in sociology.
“In sociological research, the focus has often been on the family environment and on what children do or do not learn from their parents in order to understand why relationship breakdown tends to run in families. My research shows that ‘genetic family similarity’ also plays a role,” she concludes.
In another article in the PhD project, Jørgensen compared adoptive families with families with biological children to separate genetic inheritance from environment. Here, too, the goal was to find out how parents’ relationship breakdown affects the likelihood that their children will also experience a breakup.
“Adopted children do not share genetics with their adoptive parents, so by making this comparison we can to a greater extent control for the fact that parents and children are partly genetically similar. We find that adoptive parents’ breakups have a much weaker association with adoptive children’s breakups, compared to families with biological children,” she says.

Genetics is not destiny
Despite the findings, Ruth Eva Jørgensen warns against using genetics as a kind of answer key for whom one should choose as a partner, and stresses that genes are only one part of the picture and cannot be understood as destiny.
“Genes contribute to making us different, but they act together with our life history, our environment, our partner and everything else that happens in life.”
The history of genetic research makes her particularly aware of this.
“This field has a rather ugly history involving eugenics, racism and discrimination. That is why it is especially important to avoid a deterministic interpretation of what we find, and instead try to understand how genetics and environment work together,” says Ruth Eva Jørgensen.