Researchers from the University of Wisconsin-Eau Claire in the US asked participants to list benefits and drawbacks of having opposite-sex friends.
Thirty-two per cent listed feelings of attraction as a cost, while just 6 per cent listed these feelings as a benefit, MyHealthNewsDaily reported.
Women were more likely than men to say attraction was a drawback: 47 per cent of women aged 18 to 23 listed attraction as a cost of an opposite-sex friendship, while 22 per cent of men said the same.
Opposite-sex friendships could even harm romantic relationships as 38 per cent of women and 25 per cent of men aged 27 to 50 said their partners were jealous.
In addition, the more attraction that people felt in an opposite-sex friendship, the less satisfied they were with their current romantic relationship, the study found.
"Our findings implicate attraction in cross-sex friendship as both common and of potential negative consequence for individuals' long-term mateships," the researchers said.
In a separate study, 88 college-age men and women came to the laboratory with an opposite-sex friend, and the pairs were surveyed about that particular friendship.
Participants rated their level of attraction toward their friend on a scale of one to nine.
On average, men rated their level of attraction toward their female friends as a five, while women rated their level of attraction to their male friends as a four.
Men and women reported about the same level of attraction toward their friends regardless of whether they were currently involved in a romantic relationship.
The researchers hypothesised that interacting with a member of the opposite sex instinctually triggers mating strategies that evolved tens of thousands of years ago.
"Mating strategies may influence people's involvement in cross-sex friendships to begin with, as well as unintentionally color people's feelings toward members of the opposite sex with whom their conscious intent is platonic," the researchers said.
The study was published the Journal of Social and Personal Relationships.
