Couples who had sex the earliest — such as after the first date or within the first month of dating — had the worst relationship outcomes.

“What seems to happen is that if couples become sexual too early, this very rewarding area of the relationship overwhelms good decision-making and keeps couples in a relationship that might not be the best for them in the long-run,” study researcher Dean Busby, of Brigham Young University’s School of Family Life, told LiveScience.