Couples who have more sex are not necessarily any happier, new research has found.

The study of American couples found those who had sex once a week were the happiest  - and that contentment did not increase with more frequent intimacy.

The research was based on surveys of 30,000 American couples’ sex lives over the past four years.

Dr Amy Muise, a sexuality and relationship researcher at the University of Toronto who led the study, said: "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 everyday as long as you're maintaining that connection."

The study, conducted for the Society of Personality and Social Psychology, also found that the stereotypes around sexual appetites diminishing as people get older were untrue, with their findings being consistent across all age groups.

Dr Muise said the research did not establish a causal link between the two factors, stressing it it did not necessarily show that having sex once a week made couples happier - or that happy couples have more sex.

But she said it was "important to maintain an intimate connection with your partner without putting too much pressure on engaging in sex as frequently as possible".