They were portrayed as self-satisfied and insufferable by Bridget Jones’s Diary, but research suggests cohabiting couples may have something to be smug about: they have a lower risk of depression than singletons.

A large-scale analysis involving more than 100,000 individuals across seven countries has added weight to previous research suggesting that being married or in a “marriage-like” relationship could bring health benefits.

While the researchers do not advocate dashing down the aisle to dodge depression, saying personal circumstances and broader social factors also play a significant role in mental health, they claim their research could help inform strategies for tackling the condition in society.

“The study underscores the importance of developing culturally-sensitive interventions and support systems to address the elevated depression vulnerability among unmarried individuals, particularly those with higher risk profiles based on country, sex and education level,” said Dr Kefeng Li, co-author of the research from Macao Polytechnic University, China.

Writing in the journal Nature Human Behaviour, the team report how they first analysed data from 106,556 participants in seven countries – including China, the UK, the US, Indonesia and South Korea – 22,490 of whom reported having depressive symptoms.

After taking into account factors such as age, sex, education, smoking status, body mass index and health conditions, the team found that people who did not live with a partner had an 86% higher chance of having depression than those who did.

“Unmarried but cohabiting participants were considered as ‘married’ in this study,” said Li. The study did not look at the impact on non-cohabiting relationships.

The odds were elevated regardless of whether unmarried people were single (79% greater odds of depression than married people), divorced or separated (99% greater odds), or had been widowed (64% greater odds).

The team said the association was particularly strong in western countries among men, and in people with higher levels of education. That, they suggest, could be due to cultural differences in how emotional distress is tolerated, with women having larger and stronger social support networks, and more highly educated individuals potentially experiencing greater pressures and demands.

The team also enrolled 20,865 participants from five countries and followed up with them for four to 18 years.

Overall, 4,486 participants reported developing symptoms of depression, with the analysis revealing that alcohol consumption could be a reason for unmarried people having a higher risk of depression – at least in China, Mexico and South Korea – with smoking another possible factor in China and Mexico.

The team say these results could be linked to married adults tending to have lower rates of alcohol and tobacco consumption.

The researchers also said marriage may bring benefits through better access to economic resources, social support and spouses having a positive influence on each other’s mental wellbeing.

However, the study has limitations, including its reliance on self-reported depressive symptoms, its inclusion of only heterosexual couples, and the way it is based on associations.

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“It does not prove that being unmarried directly causes depression or that getting married would prevent or cure depression,” said Li, adding that the quality of a marital relationship is probably also important but was not considered in the study.

Dr Veronica Lamarche of the University of Essex, who was not involved in the study, said previous research had revealed health benefits of being in a relationship compared with being single.

However, she also said the quality of a relationship is important. Indeed, a recent study suggested that conflict within a marriage can be damaging for mental health.

“Crucially, this [study] should not be seen as a motivation to go out and get married for the sake of it,” Lamarche said.

“There is a growing body of research showing that people who are single by choice and feel comfortable in that stage in life show similar health outcomes to people who are in a relationship.

“People also get many of the same health and wellbeing benefits from their connections with close friends and family as they do from marital partners. What matters here is not ‘being married’ v ‘not being married’, but the quality of the relationships we cultivate.”