Romantic partners are often a major source of support, stability, and shared experiences. But they can also shape our habits and behaviors in subtle ways. Married couples spend a lot of time together (more than four hours per day, on average), giving partners plenty of opportunities to influence one another.1
Research shows that partner characteristics can have wide-ranging effects. For example, individuals with more organized and reliable partners are more likely to get a promotion at work, and having a happier spouse is associated with lower mortality.2,3
In a recent study published in Clinical Psychological Science, my colleagues and I examined how romantic partners influence drinking behavior, including both alcohol consumption (the number of drinks consumed each month) and binge drinking (how often someone consumes five or more drinks in one sitting).4
Some findings were unsurprising: Individuals tended to drink more and binge drink more frequently if their romantic partner also drank alcohol or smoked cigarettes. These shared habits are common in close relationships. However, we also found evidence for a more complex process through which partners shape drinking behavior: gene-environment interaction.
What Is Gene-Environment Interaction?
Gene-environment interaction, or G x E, occurs when the effect of genetic factors depends on environmental features. The “environment” can include many things: diet, stressors, pollutants, or social relationships.
We found that romantic partners’ personality traits and mental health interacted with genetic factors to influence binge drinking. Genetic influences on binge drinking were weaker for individuals whose partners were more conscientious. In contrast, genetic influences were stronger when partners were more extraverted, neurotic, and distressed.
How Might This Work?
Shanahan and Hofer’s mechanisms for G x E provide one helpful way to understand these findings.5
For example, having a partner who is distressed and high in neuroticism (a personality trait linked to anxiety, depression, and self-doubt) may create a stressful environment. Stress can trigger or amplify a genetic predisposition to alcohol misuse. On the other hand, a conscientious, reliable, and organized partner may compensate for genetic liability by providing structure and support.
Extraverted partners likely influence drinking differently. Because extraverted people tend to be more socially active, their partners may spend more time in social settings where alcohol is present, creating more opportunities to drink.
Why It Matters
These findings highlight the important and complex ways in which romantic partners shape health behavior. From a clinical perspective, the results may also help inform couples-based approaches to alcohol treatment. Many couples-based interventions focus on communication and conflict, but partner personality and mental health may also play an important role.
This study suggests that our closest relationships can shape how genetic factors influence alcohol misuse. Even in supportive relationships, a partner’s habits, personality, and mental health can subtly affect our behavior.