Examining cultural background and the protective effect of marriage on alcohol use disorder in Sweden

Background Little is known about whether the protective effect of marriage on alcohol use disorder (AUD) varies by cultural background. Aims Using Swedish national data, we examined whether marriage is associated with a stronger reduction in AUD risk among Swedes of a Swedish background (i.e. those with two Swedish-born parents) compared to Swedes with a foreign background (i.e. one or two foreign-born parents) and whether the protective effect of marriage depends on whether the spouse has a Swedish or foreign background. Method Among those born in Sweden 1960 to 1990 (3,093,439; 49% female), associations between cultural background and AUD registration during marriage were estimated with Cox models. Analyses of intra- and intermarriage on AUD registration were examined with Cox models and limited to groups of focal individuals for which there was sufficient statistical power, which included Swedes with two Swedish-born parents, two Finnish-born parents, or bicultural background (one Swedish and one foreign-born parent). Models were sex stratified. Results Marriage was associated with reductions in AUD risk among those with Swedish and with foreign backgrounds, though less protective for males of Finnish versus Swedish background as indicated by a significant interaction between marital status and parental region of birth, HR = 0.80, 95% CI [0.71, 0.90]. Marriage was also less protective for those with a bicultural versus Swedish background, HR males = 0.87, 95% CI [0.81, 0.92] and HR females = 0.88, 95% CI [0.81, 0.97]. Among those of Swedish background, marriage to a spouse with a foreign versus Swedish background was associated with increased risk of AUD, HR males = 1.26, 95% CI [1.19, 1.34] and HR females = 1.20, 95% CI [1.10, 1.31]. This risk was diminished when family-level confounders (genes, rearing environment) were controlled for. Conclusions The protective effect of marriage depends on cultural background, with some evidence that increased risks associated with a spouse’s foreign background are confounded by family-level factors.