Married people have fewer depressive symptoms than unmarried people, large international study finds

A new study published in Nature Human Behaviour reveals that unmarried individuals, regardless of whether they are single, divorced, separated, or widowed, tend to experience depressive symptoms more often than their married counterparts. However, the size of this difference varies based on factors such as country of residence, sex, and education level. The study also found that alcohol use and smoking might explain some of the increased risk of depressive symptoms among unmarried individuals in China, Korea, and Mexico.

Depression is a major public health concern worldwide, affecting an estimated 5% of adults globally. This rate is expected to rise in the coming years, potentially exceeding 10% by 2025. Depression is linked to a range of negative health outcomes, including an elevated risk of heart disease, disability, and suicide. Thus, identifying factors that contribute to depression is essential for developing effective prevention and treatment strategies. Given that marriage is a significant social bond with potential implications for health, researchers sought to investigate its relationship with depression across different countries.

Previous studies, primarily conducted in Western countries, have suggested that being married might offer some protection against depression. However, these findings might not apply universally due to cultural, socioeconomic, and educational differences between countries. Some research, for example, did not find a relationship between marital status and depression in women in Korea and Kenya. To address this gap, the researchers conducted a large-scale, cross-country analysis to provide a more comprehensive understanding of the association between marital status and depression.

The researchers utilized a large-scale, two-stage analysis that combined data from several nationally representative cohorts across seven countries: the United States, the United Kingdom, China, Korea, Mexico, Indonesia, and Ireland. In the first stage, a cross-sectional analysis examined the relationship between marital status and current depressive symptoms. This analysis included 106,556 participants from various national health surveys conducted between 2005 and 2020. The researchers categorized participants into four marital status groups: married, single, divorced or separated, and widowed.

Depressive symptoms were measured using standardized questionnaires specific to each country, such as the Patient Health Questionnaire-9 and the Center for Epidemiological Studies Depression scale. To isolate the effect of marital status on depressive symptoms, the researchers controlled for potential confounding factors, including age, sex, educational attainment, income, and health behaviors such as alcohol consumption and smoking.

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In the second stage, a longitudinal analysis was conducted to explore the causal pathways between marital status and later development of depressive symptoms. This part of the study followed 20,865 participants from five countries over several years, tracking changes in depressive symptoms and examining the mediating effects of alcohol and smoking. The researchers used statistical techniques, including causal mediation analysis, to assess whether these health behaviors played a role in the observed relationship between marital status and depression.

The results of the study showed that, overall, unmarried individuals had a higher likelihood of experiencing depressive symptoms than married individuals. This pattern held true across all countries studied, with unmarried people having nearly double the odds of reporting depressive symptoms compared to those who were married. The pooled odds ratio for depressive symptoms among unmarried individuals was 1.86, indicating a substantial increase in risk.

However, the magnitude of this increased risk varied depending on specific factors. For instance, the association between being unmarried and depressive symptoms was more pronounced in Western countries like the United States, the United Kingdom, and Ireland compared to Eastern countries such as China, Korea, and Indonesia. The researchers suggest that cultural differences in social expectations, emotional expression, and coping mechanisms might explain why unmarried individuals in Western societies are more vulnerable to depression.

Sex was another important factor that influenced the relationship between marital status and depression. The researchers found that unmarried males had a higher risk of depressive symptoms compared to unmarried females, particularly among single individuals. This finding aligns with previous research suggesting that males may have fewer social support networks and face greater societal pressure when they are unmarried, potentially increasing their susceptibility to depression.

Educational attainment also emerged as a significant moderator. Unmarried individuals with higher levels of education experienced a greater risk of depressive symptoms compared to those with lower educational attainment. The researchers hypothesize that highly educated individuals may face increased societal expectations and career pressures, which, when combined with a lack of spousal support, could exacerbate psychological distress.

In the longitudinal analysis, the researchers found that alcohol use and smoking played a causal role in the development of depressive symptoms among unmarried individuals in China, Korea, and Mexico. For example, alcohol use accounted for 3.2% of the risk of developing depressive symptoms among single Mexicans, 34.1% among single Koreans, and 27.4% among single Chinese. For divorced/separated individuals in these countries, alcohol use accounted for 16.5%, 29.3%, and 21.2% of the risk, respectively. Among widowed individuals, alcohol use accounted for 13.4%, 5.9%, and 12.0% of the risk in Mexico, Korea, and China, respectively. Smoking was also found to be a significant mediator among single individuals in Mexico and China, accounting for 22.1% and 43.8% of the risk, respectively. However, alcohol use and smoking did not significantly mediate the relationship between marital status and depressive symptoms in the United States or Ireland.

The researchers found that these health behaviors explained a significant portion of the increased risk, suggesting that interventions aimed at reducing alcohol and tobacco use could be effective in mitigating depression among unmarried individuals.

Despite its comprehensive approach, the study has some limitations. First, it relied on self-reported measures of depressive symptoms, which may not fully capture the complexity of clinical depression. Additionally, the study was limited to heterosexual relationships due to the lack of data on same-sex partnerships, and the findings may not be generalizable to all cultural contexts.

Future research could address these limitations by including clinical diagnoses of depression and exploring the impact of marital status in more diverse relationship contexts. Moreover, further investigation into the cultural factors that influence the association between marital status and depression could provide deeper insights into the social determinants of mental health.

Despite these limitations, the study provides insights into the relationship between marital status and mental health across different countries. The findings suggest that unmarried individuals, particularly those who are single, highly educated men in Western countries, may be at a higher risk of developing depressive symptoms.

The study, “Association and causal mediation between marital status and depression in seven countries,” was authored by Xiaobing Zhai, Henry H. Y. Tong, Chi Kin Lam, Abao Xing, Yuyang Sha, Gang Luo, Weiyu Meng, Junfeng Li, Miao Zhou, Yangxi Huang, Ling Shing Wong, Cuicui Wang, and Kefeng Li.