In the run up to Valentine's day, a new report suggests that couples that pray together on a regular basis are happier, on average, than those who do not.

A couple that prays together at least once a week is 17 per cent more likely to say they are happy together, according to the report by the Institute for Family Studies.

The reasons given for this include that joint prayer is likely to "engender a heightened sense of emotional intimacy, communication and reflection about relationship priorities and concerns, and a sense of divine involvement in one's relationship."

"However it works, in our statistical models, shared prayer is a stronger predictor of relationship quality than other religious factors," said the study. "It is also a better predictor of relationship quality than race, education, age, sex, or region."

The report analysed a national sample of 1,600 adults (18-59) in heterosexual romantic relationship, taken from the 2006 National Survey of Religion and Family Life.

It found that 78 per cent of couples who attend church together said they were "very happy" or "extremely happy". By comparison, 67 per cent of couples who do not attend church said the same thing.

Reasons for this increased level of happiness include having shared friends in the church. "Enjoying shared friendships in a religious congregation may boost relationship quality by giving such couples a sense of belonging and community, as well as other models of successful relationships," the report said.

"We emphasize that some of the benefits of religious participation appear to be temporal, not spiritual, and hold even for churchgoers who may be uncertain about their own devotion."