The study for Marriage Care - as well as Relate and Relationships Scotland - concluded mistrust and doubt levels are two and a half times higher among unmarried couples who live together.
Jenny Porter, head of client services, at Marriage Care told also told Premier the commitment required in a marriage means wed couples are more likely to stay together.
She said: "It's in the vowels that you make within the marriage service ...that you're making this commitment and I think, therefore, it's much more upfront what you're doing. You know what you're going into."
While 15 per cent of cohabiting couples had concerns over the commitment of the partner to their relationship, the figure was found to be six per cent for married couples.
Jenny Porter went on to say: "The difference sometimes with people who cohabit is that ...they don't always have that really upfront conversation about what this is we're going into."
The YouGov survey involved 5,000 people.
It also found more than two thirds of people believed trust is important, while 52 per cent valued communication and 37 per cent said commitment mattered.
Explaining why marriage should be celebrated, Jenny added: "It is this beautiful commitment that we make to ourselves and we make in front of God. There is research out there that shows healthy, committed relationships are good for us."
Listen to Jenny Porter speaking with Premier's Alex Williams: