You can’t have too much of a good thing, can you? And sex is definitely a good thing. Several studies show that couples are likely to be satisfied with their relationship when they have more sex. But small kids, work worries or a new Scandinavian crime series can downgrade sex as the activity of choice. So wouldn’t it be nice to know exactly how much sex you need to have a happy relationship?

The solution

Well, according to a study in the journal Social Psychological and Personality Science, the magic number is once a week. The study used data on sexual frequency and happiness from more than 30,000 Americans who took the General Social Survey between 1989-2012. The survey found that couples were happier if they had more sex, but that more than once a week didn’t increase their happiness. The once-a-week rule held true regardless of age, sex, or length of relationship. The study found no link between happiness and how often someone had sex if they were single.

Amy Muise, the lead author, says that this is the first study to show a curvilinear relationship between sex and happiness – that the association levels off at once a week rather than being linear.

The take-home message, she says, is that the pressure is off – the average person doesn’t have to have sex as often as possible. “Sex,” she says, “does not have limitless benefits for wellbeing such that more is always better. Instead, it seems that only too little is bad.”

While other studies show that men report higher sexual desire than women, this research suggests that having sex more than once a week doesn’t make them any happier. The study did not look at quality of sex, but research suggests that couples feel mostly positive about their sexual experiences. Muise says positive feelings about sex last for at least the next day, so, strictly speaking, it is unlikely that daily sex is ever necessary.

The average amount of sex that couples have is, in fact, once a week, though this is not the optimum amount of sex if you are trying for a baby.

This new study shows only an association, not causation, but it follows a study published last May in the Journal of Economic Behavior and Organization that found couples who were having sex about once a week and were asked to double their amount of sex enjoyed it less and were slightly less happy than before. The authors concluded that asking couples to have more sex may not be the best idea – people have to want to initiate it for themselves, not for a research study. Muise’s study did not find that more sex made couples unhappy – only that having too little had that effect.