Long-term committed relationships are good for mental and physical health and this benefit increases over time. On average, married people also live longer, say David and John Gallacher from Cardiff University.

According to the authors, women in committed relationships have better mental health, while men in committed relationships have better physical health.

Men's physical health probably improves because of their partner's positive influence on their lifestyle. (One perfect example would be that he eats less fast food when you cook at home.) For women, the mental bonus may be due to a greater emphasis on the importance of the relationship.

Not all relationships are good for you, however. People in strained relationships or with a troubled marriage fare worse in the mental health department than single folks. As do couples who are facing break-ups or divorce. Having numerous partners is also linked with a risk of earlier death.

But even though relationship failures can hurt your health, that's no reason to avoid them altogether. A good relationship will improve both physical and mental health and perhaps the thing to do is to try to avoid a bad relationship rather than not getting into a relationship at all, conclude the authors.