Fig. 1

Possible explanations for spousal concordance on alcohol use. a Assortative mating. Alcohol behaviour influences mate choice; individuals are more likely to select a mate with similar alcohol consumption. b Social homogamy or confounding. An unknown confounder, X, influences mate-selection independent of alcohol behaviour. For example, ancestry or socio-economic status may influence both alcohol use and mate choice. c Partner interaction effects. During the relationship, spouses influence each other’s alcohol consumption. For example, spousal alcohol consumption could become more similar over time. d Relationship dissolution. Spouse-pairs with more similar alcohol behaviour are more likely to remain in a relationship and be recruited into UK Biobank or similarly, are more likely to participate in the study together