You can finally stop feeling inadequate watching those old re-runs of Sex and the City. A study has found that couples in relationships should have sex once a week for optimum happiness. In one of the largest investigations of its kind, researchers analysed data on the relationship between sex and happiness.

The extensive surveys by The Social Psychological and Personality Science collected data from more than 11,000 men and 14,000 women who responded to the General Social Survey between 1989 and 2012. The analysis of results have found that, contrary to previous reports that more sex equals happier couples, once a week actually makes the happiest relationships.

Interestingly, the study reports that having more sex will make couples no more or less happy than the once-a-weekers.

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Amy Muise, the lead researcher from the University of Toronto Mississauga, said there was 'a linear association between sex and happiness up to a frequency of once a week, but at higher frequencies there is no longer an association.

'Therefore it is not necessary, on average, for couples to aim to engage in sex as frequently as possible.'