Marriage has long been thought to be beneficial - both in sickness and in health.
But a study suggests that widows actually suffer less stress and frailty than wives whose husbands are still alive. The findings are in contrast to previous research which showed marriage has a protective effect on health, lowering the risk of heart attack and depression, and increasing the chance of surviving from cancer.
The study, by the University of Padova, in Italy, found that while men suffer negative consequences when their wives die - because they rely more heavily on their spouses - women appear to get healthier.
Dr Caterina Trevisan, lead researcher on the study, said the presence of a wife may bring benefits for men in terms of household management and healthcare, whereas women are "more likely to feel stressed and find their role restrictive and frustrating".
She said: "Since women generally have a longer lifespan than men, married women may also suffer from the effects of care-giver burden, since they often devote themselves to caring for their husband in later life."
Dr Trevisan said these factors may be behind the lower risk of depression in unmarried women. The same study also found single women experienced less anxiety than bachelors, greater job satisfaction and higher activity levels at work, and a lower risk of social isolation as they maintained stronger relationships with family or friends.
"Consistently with this picture, the higher educational level and better economic status seen among the single women in our study may well reflect a social condition that would promote a greater psychological and physical well-being," added Dr Trevisan.
"Finally, widows cope better than widowers with the stress deriving from the loss of a partner and widowhood, with a significant increase in the risk of depression only in the latter. Many studies have shown that women are less vulnerable to depression than men in widowhood, probably because they have greater coping resources and are better able to express their emotions.
"These aspects may help to explain the lower risk of exhaustion seen in single women, who are likewise more socially integrated than single men."
It is well known married people generally live longer than their single counterparts, who are said to have a worse diet and drink more alcohol. But the study of almost 2,000 over-65s shows the association between marital status and fitness has "gender specific differences" among older individuals.
Most notably, widows were about 23 per cent less likely to be frail than married women, reports the Journal of Women's Health.
There was no significant link to frailty for elderly spinsters, who were also less likely to suffer weight loss and exhaustion than women who were married.
The study followed 733 Italian men and 1,154 women for four and a half years.