Couples should have sex once a week for optimal happiness, a new US study has suggested.

The findings were based on surveys of more than 30,000 Americans collected over four decades, and were published in the journal Social Psychological and Personality Science on Thursday.

Less frequent sex decreased happiness, but more frequent lovemaking did not increase it, the study found.

• How to win big in the game of love
• When should a boyfriend or girlfriend become a ‘partner’?
• We’re all going to be making love to robots, apparently

Sex once a week may be enough. Photo: Getty

“Our findings suggest that it’s important to maintain an intimate connection with your partner, but you don’t need to have sex every day as long as you’re maintaining that connection,” lead researcher, University of Toronto-Mississauga’s Dr Amy Muise, said in a statement.

An Australian relationship expert agreed that physical intimacy was just the “icing on the top” of a couple’s closeness, with many other factors just as important.

Relationships Australia counsellor Val Holden said that while frequency of sex was a contentious topic for many couples, the ideal number varied, with some relationships able to survive without it.

“I’ve had couples that haven’t had sex for 14 years. I’ve had other couples that have sex once a year and then you have other couples that have sex once a day,” Ms Holden said.

“I would be saying that it’s not so much the frequency that affects the couple’s relationship intimacy [but] what their intimacy level is like other than having sex, so what other things do they do together, what’s that like, how happy are they in their relationship, and then sex is the icing on top of that.”

Factors other than sex may be just as important. Photo: Getty

Another relationship expert strongly disagreed, saying a lack of physical intimacy was often the result of the many distractions of modern life.

“Stress, work, friends and other things get in the way, whereas if your primary focus was your partner, you would be having sex much more frequently,” Curtin University relationship expert Amanda Lambros said.

The study’s authors noted it was not designed to show cause-and-effect, so it remains unknown whether happiness leads to weekly sex, or if weekly sex arouses more joy in life.

The study was also limited to people in romantic heterosexual relationships, not single people or same-sex couples. The findings were consistent across age groups, gender and the length of the relationship, whether months or decades.

The study’s author, Dr Muise, said couples should discuss whether their sexual needs were being met, rather than simply press for more sex.

“It’s important to maintain an intimate connection with your partner without putting too much pressure on engaging in sex as frequently as possible,” she said.

An Australian sex expert echoed the importance of not putting too much pressure on a reluctant partner.

Couples should communicate openly about their intimacy needs. Photo: Getty

“I think the right amount for a couple is whatever they negotiate between them as a couple and what feels satisfying and achievable for them,” Sydney sexologist Amanda Robb said.

“I do think this research will provide relief for couples who are feeling pressure to perform sexually more than their libido or lifestyles allow them to on a weekly basis.”

For couples who squabble about sex, Ms Robb recommended open and frank discussion.

“My first suggestion is to acknowledge it. Once a couple can identify an imbalance in libido and furthermore be okay with this, then they will be able to work around it in a much more harmonious and manageable way,” she said.

“Talk early on in the relationship about any sexual hopes you might each have. This can instantly alleviate any false expectations on how often you need to have sex to ‘satisfy’ your partner.

“Also remember, sexual engagement does not always involve the act of sex itself. Taking turns with foreplay and other intimate activities can be just as satisfying and at times feel more giving than sex.

“Once again, talk with each other about what your needs and wants are to then hopefully gain an idea of how your sexual relationship and frequency will take place.”

-with Jackson Stiles and AAP