Genetic Sensitivity to the Positive Effects of Relationship Education

Study Background

Problems in couple relationships can have negative effects on mental and physical health. But research shows that it is possible to prevent common relationship problems with specifically designed psychological programmes.

The Prevention and Relationship Education Program (PREP) is one of the most established and tested interventions to equip couples with important relationship skills. PREP is a relatively short programme that can be delivered in as little as 12 hours across two weeks and teaches participants about relevant aspects of relationships such as communication, problem-solving, and emotional support through a range of engaging activities. According to empirical studies, PREP tends to improve communication skills and relationship quality whilst also preventing divorce.

What hasn’t been investigated yet is whether sensitive people benefit more from the positive effects of such interventions although it is well known that people differ substantially in their sensitivity: some are generally more and some generally less sensitive to both negative and positive experiences. It has been shown that such individual differences in sensitivity have a genetic basis.

Over the years, a small number of individual gene variants with well-known biological function (i.e., so-called candidate genes) have been associated with differences in sensitivity to both negative and positive experiences. More recently, progress in molecular genetics has led to the development of new methods that capture even very small genetic associations with sensitivity across the whole genome (irrespective of whether the biological function of the gene variant is understood or not). This results in many thousands of genetic associations that can then be summed up in so-called polygenic scores.

In our study (1) we set out to investigate whether differences in genetic sensitivity predict the degree to which people benefit from relationship intervention. We expected that genetically more sensitive individuals would benefit more than less sensitive ones.

Study Design

In order to test the influence of genetic sensitivity on the response to relationship intervention, we collected genetic samples from couples (representing 242 individuals) that previously participated in a large randomised controlled trial (RCT) on PREP. This means that some of the couples were randomly allocated to PREP and some to a control condition (with no intended effects on relationship quality).

Couples reported on a range of relationship aspects before and directly after the intervention ended and then every six months for up to two years. The measures included questionnaires on marital satisfaction, communication skills, positive bonding, and risk for divorce.

The collected genetic samples (saliva) where analysed in the lab in order to create two different indicators of genetic sensitivity. Nine well-known candidate gene variants were combined to create a candidate gene polygenic score. In addition, we also created a genome-wide polygenic score that included close to 65,000 gene variants.

We then tested whether these polygenic scores for sensitivity influenced the short-term response to the intervention as well as the long-term effects on the different aspects of relationship quality in the two years following the intervention.

Given that genetic studies require large samples, we repeated the same analyses in an independent study with 160 individuals. We also tested a more stringent genome-wide polygenic score that included only the 8,112 gene variants that were most strongly associated with sensitivity.

Key Findings

We found that the polygenic score based on the nine candidate genes did not influence the effects of the PREP intervention. However, the genome-wide polygenic score was associated with stronger long-term treatment effects on all four measured aspects of relationship quality.

Individuals with higher genetic sensitivity improved more in marital satisfaction, communication and positive bonding than less sensitive individuals when allocated to PREP. They also showed lower increases in the risk for divorce. In Figure 1 we provide a graphic illustration of the findings for communication skills. Genetically sensitive individuals that attended PREP showed an increase in communication skills after PREP. But genetically sensitive individuals in the control condition showed a decrease. Individuals with low genetic sensitivity showed a reduction in communication skills regardless of whether they were allocated to PREP or the control condition. This suggests that genetically sensitive individuals benefitted most from the positive effects of PREP.

Interestingly, genetic sensitivity did not predict differences in the response to the treatment straight after PREP. Differences emerged only in the two years following the intervention. This could mean that the positive effects start slowly emerging as sensitive individuals continue to apply the acquired skills even a long time after PREP ended.

Finally, similar results emerged in the second sample and when using the more stringent genome-wide polygenic score.

Conclusion

Our study provides further evidence that genetic sensitivity influences whether people benefit from psychological interventions. According to our findings, individuals with higher genetic sensitivity seem to benefit significantly more from a relationship programme compared to those with lower genetic sensitivity. This suggests that genetically sensitive people are especially suited for such programmes.