Getting married may be bad for men's health but good for women, according to a study.
Whose mental health is this helping?
Researchers found that men who get hitched are more likely to suffer mental health problems than those who simply live with their partners.
The opposite is true for women - but they do best without any relationship.
The study, published in the Journal of Epidemiology and Community Health, suggests men who stay single are most likely to suffer from depression.
Researchers at Queen Mary University London questioned over 4,000 men and women under the age of 65 across Britain.
They found that men and women whose first relationship lasts stand to reap the rewards later in life. They are least likely to suffer mental health problems.
Unsurprisingly perhaps, the researchers found that the risk of problems increases if that relationship breaks up.
A string of failed relationships has a similar effect. However, women appear more vulnerable than men.
The study also found that women take longer to recover after a break-up than men.
In fact, they may be best to avoid men altogether.
The researchers found that women can survive quite well without a relationship.
Those who had never been in a relationship were much less likely to report having a mental health problem than those who had moved in with a man or got married.
However, once in a relationship women appear to do better if they have a ring on their finger.
Women who cohabitated with men were more likely to suffer problems than those who were married.
The researchers suggested that this may be because they do not enjoy as many rights as married women.
"The lack of protection of the financial and property rights and hence the security of cohabiting couples when they separate may explain why women who cohabit have poorer mental health than women who marry," they wrote.
They suggested that the findings should prompt MPs to consider changing the law to ensure these women had the same rights as those who are married.
"Parliament should review the law in relation to cohabitation rights," they said.
Paula Hall, a relationship counsellor at Relate, said the findings may reflect the different needs of men and women.
"For women, security is more important," she told BBC News Online.
"They are the ones who have babies and they have very strong nurturing and protective instincts. That may be one reason why marriage is more important to them.
"For men, security is less of an issue. Feeling trapped is a bigger problem for them. That may be why they fare better if they cohabit rather than marry.
"However, that's all just a hypothesis. Another study published last year said men and women are happier if they marry."