Alcohol use is shaped by many things, including family history, stress, friends and the people we live with. A Finnish study asked how a partner's own habits and personality might be linked to the way genetic risk for heavy drinking plays out. The answer is complex, and it does not support blaming a partner for anyone's drinking.
This article is general information about one study. It is not medical advice and does not suggest anyone should change their drinking or relationship. If alcohol is a concern for you or someone close to you, a GP or an alcohol and other drugs service can help. In Australia, Lifeline is on 13 11 14, and 000 is for emergencies.
The study was led by Mallory Stephenson and Jessica Salvatore, working with colleagues at Virginia Commonwealth University and Rutgers Robert Wood Johnson Medical School, and with co-authors in Finland. It was published in Clinical Psychological Science in May 2025, with funding from the US National Institute on Alcohol Abuse and Alcoholism and the Academy of Finland.
They used anonymised data from FinnTwin16, a long-running study of Finnish twins. The sample was twins in their 30s who were in long-term relationships and had a history of alcohol use. Surveys from 1,620 twins and their partners covered drinking, smoking, personality and mental health.
A twin design compares identical twins, who share almost all their genes, with fraternal twins, who share about half. By comparing the two, researchers can estimate how much of a trait reflects genes and how much reflects environment. They then tested for gene-environment interaction, which asks whether the influence of genes changes depending on a person's circumstances, in this case their partner's characteristics.
Consistent with earlier research, a person was more likely to drink, and to binge drink, if their partner frequently drank or smoked. Among identical twin pairs, partners appeared to have more influence on the drinking of male twins than of female twins.
The main new finding was about interaction. Genetic influence on binge drinking appeared stronger when the partner smoked more often, was less conscientious, was more extroverted, or reported higher neuroticism or psychological distress. In other words, the same underlying genetic risk seemed to show up more in some partnership settings than others.
One result was unexpected. Genetic influence on binge drinking appeared weaker when the partner drank more often. The researchers described this as surprising, and one suggested explanation is that heavy partner drinking may shift the balance toward environmental influence and away from genetic influence. This was an idea offered by the authors, not a tested conclusion.
The researchers suggest the work could eventually inform couples therapy and couple-based alcohol programs, which usually focus on how partners relate to each other rather than on each partner's individual traits.
This is an observational study. It describes patterns and modelled interactions, and it does not show that a partner causes drinking or that changing a partner's habits would change someone else's. Genetic influence here means a statistical estimate across groups of twins, not a fixed outcome for any person. Genetic risk is not destiny, and it does not mean someone will develop an alcohol problem.
The study does not justify attributing a person's alcohol problems to their partner. People choose partners who are similar to themselves, and people influence one another in both directions, which the data cannot fully separate.
The article describing the study does not report effect sizes or confidence intervals, so how large the interactions were is not clear. The participants were Finnish twins in their 30s, so the results may not apply to other ages, cultures, relationship types or to people who are not twins. The unexpected finding about partner drinking has not yet been explained, and the research team says more work is needed, including on relationship quality and parenthood.
If you or someone you care about is worried about drinking, there is no need to work out whose habits "started it". Support is available without blame. Never change medicines or stop drinking suddenly without medical advice if you drink heavily, as that can be unsafe.
Source: Associations of Romantic Partners' Characteristics With Alcohol Consumption and Binge Drinking: Examining Evidence for Gene–Environment Interaction DOI: 10.1177/21677026251332931
Conceptual illustration of partners reflecting on shared drinking habits. AI-generated editorial illustration. This article summarises published research in our own words and is general information, not personal health advice.
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