A good, lasting marriage makes the spouses happier and healthier and increases their lifespan, compared with cohabitation. On average. That’s the net finding of a review of 148 studies in seven European countries, according to an editorial in the British Medical Journal.

So don’t let anyone kid you otherwise. A recent report from a New Zealand cohort study said that cohabiting relationships made the partners just as happy as marriage if they lasted. But they do not usually last as long as marriages, and that’s a fact.

John Gallacher, the Cardiff University academic who did the recent European review, says that as long as the relationship is loving and supportive, the partners are likely to eat healthily, have more friends and take better care of each other. It’s all down to commitment:

‘Marriage and other forms of partnership can be placed along a sliding scale of commitment, with greater commitment conferring greater benefit,’ he added.

‘That marriage generally indicates a deeper commitment might explain why marriage is associated with better mental health outcomes than cohabiting. Cohabiting relationships tend to be less enduring. The most widely accepted explanation is that being in a committed relationship means better social support is available.

‘Commitment seems to provide networks of supportive and helpful relationships, beginning with the spouse or partner, leading to more healthy lifestyles and better emotional and physical health.’

Commitment, of course, means exclusivity:

‘The take home message is simple. Exclusive and supportive relationships confer substantial mental and physical health benefits that grow over time,’ he added.

I think there are some other good points in this study, and will get hold of the original.