Thinking of moving in with your partner but hearing an earful from your mother?Meet your ammunition: A new study in the February issue of the Journal of Marriage and Family found that cohabitating couples are happier than married ones.Using data from the National Survey of Families and Households, the researchers looked at wellbeing among 2,737 single men and women, 896 of whom married or moved in with a partner over a six-year period. (Singles weren’t always partner-less, just unmarried and living separately.)Shortly after marrying or moving in together, couples were happier and showed fewer depressive symptoms than singles—but the benefits faded quickly. And single people kept closer ties with parents and friends, which can buffer mental health and lower stress.QUIZ: Are You Feeling Stressed?Married couples’ health improved (possibly due to joint health insurance), but those who opted to live together in unwedded bliss experienced bigger boosts in happiness and self-esteem. “For some, cohabitation may come with fewer unwanted obligations than marriage and allow for more flexibility, autonomy and personal growth,” lead author and Cornell professor Kelly Musick, PhD, said in a statement.While marriage certainly has its merits (tax breaks, public recognition, less incentive to shave), it isn’t the best option for everyone.As more people forgo marriage or opt to have kids out of wedlock, Musick highlights the importance of considering the benefits of more diverse family structures. “These changes have blurred the boundaries of marriage, leading to questions about what difference marriage makes in comparison to alternatives,” she said. According to her research, it may not make much difference in wellbeing.Of course, a six-year window at the beginning of a marriage or cohabitation is just a small slice of life and the benefits of each may change over time. Married couples may also be more likely to have children in that time period, which would temporarily lower their happiness (especially while they’re still waking up at 3 a.m. to change diapers).But the key here is that couples can be just as happy with unconventional arrangements. “Our research shows that marriage is by no means unique in promoting wellbeing and that other forms of romantic relationships can provide many of the same benefits,” said Musick.MORE: The Health Benefits of MarriageSo if your mom’s biggest concern is that he’ll never put a ring on it, remind her that if you move in together without tying the knot, you may actually get a happier ending. (She does want you to be happy, right?)