The new study suggests sex is only linked to better well-being up to one time per week. After that, there are no additional effects on happiness.
The study, led by Amy Muise - a social psychologist at the University of Toronto-Mississauga in Canada - is published in the journal Social Psychological and Personality Science.
She and her team note that the media - and other research - have supported the claim that the more sex and money we have, the happier we will feel, which represents a linear association between sexual frequency or money and well-being.
However, the researchers say couples with busy lives and work or family responsibilities may feel pressure to have sex as frequently as possible, resulting in further stress.
As such, Muise and colleagues set out to investigate whether there is a point at which frequency of sex or amount of money no longer confers additional benefits.
Their investigation involved three different studies, which used surveys of more than 30,000 Americans collected over 4 decades.
Sex once a week is the magic number for happiness
For their first study, the researchers analyzed survey responses about sexual frequency and general happiness from 11,285 men and 14,225 women who took the General Social Survey from 1989-2012.
This survey, which is conducted by the University of Chicago every 2 years, covers a wide range of sociological issues and incorporates opinions about race relations, religion and sex.
From the survey, the team found that people in established, heterosexual romantic relationships have sex about once a week on average.
And the study reveals that this is the magic number for happiness; the researchers found that happiness increased with more frequent sex, but only up to once per week. Any more than this, and there was not an observed rise in happiness.
Commenting on their findings, Muise says:
"Although more frequent sex is associated with greater happiness, this link was no longer significant at a frequency of more than once a week. 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."
Another study that assessed survey results collected over 14 years from 2,400 married couples in the US also showed that couples reported more satisfaction with their relationships as sexual frequency increased - but only up to once per week.
The researchers note that their study does not make a causal link and, therefore, does not reveal whether having sex up to once a week makes couples happier, or whether being in a happy relationship causes couples to have more frequent sex.
Furthermore, their findings are representative of married, heterosexual couples, and Muise says they did not observe a link between sexual frequency and well-being for single people.
She adds that for single people, the link between sex and well-being may be dependent on the relationship context in which the sex occurs or how comfortable single people are with sex outside of an established relationship.
Sex, more than money, linked to happiness
In an additional study, the researchers carried out an online survey involving 138 men and 197 women who were in long-term relationships. The survey included questions about their annual income.
After analyzing the results, the researchers found that there was a bigger difference in happiness between people who had sex less than once a month, compared with people who had sex once a week than between those who had an income of $15,000-25,000, compared with those with an income of $50,000-75,000 per year.
Muise says their results show sex may be more strongly linked to happiness than money and adds that "people often think that more money and more sex equal more happiness, but this is only true up to a point."
Because the couples in their study were already having sex about once a week on average at baseline, the researchers say future research could test whether increasing sexual frequency benefits couples who are having sex less frequently than once a week.
However, they add that the directive of being asked to increase sexual frequency could result in sex being less enjoyable, which poses a challenge to this avenue of study.
For men who are looking for more frequent sex in their relationships, a recent study suggested men who do their share of household chores have a better sex life.