Unless they’ve done something unspeakably awful (try it on with your best friend, accidentally set fire to your mum, etc.), it’s not unusual to want to stay friends with an ex. In fact, if you ended on reasonably amicable terms – and particularly if you move in the same social circles – attempting to maintain a friendship often seems like the most sensible, mature option.

But a recent study suggests that you should only try and stay friends with your ex if you’re certain you don’t still harbour feelings for them – or it could have serious repercussions on your future relationships.

According to the study, published in the journal Personal Relationships, people who stay in touch with their ex-partners may do so because they are not particularly committed to their new relationships – and see their ex as a potential ‘back-up plan’.

Researchers in the US performed two studies, examining the survey responses of over 400 female undergraduate students. All of the women were in relationships of at least one month, and had previously dated someone else for at least three months. (Research has found that people usually feel “committed” to a relationship around the three-month benchmark, according to the study’s authors.)

Of these women, around 40% were still in contact with their ex, with the vast majority – over 90% – communicating at least once every couple of months.

In the first survey, the women were asked about their break-up and to describe how they felt about both their current and former flames.

Read more: Apparently being friends with your ex makes you a narcissistic psychopath

In the second, researchers identified the four main motivations women said they had for staying in touch with their ex. These were: friendship reasons (i.e. “He/she is a great person; we just had bad timing”); a shared social network (i.e. “We have similar networks of friends”); investment in the former relationship (i.e. “We went through a lot together”); and keeping the ex as a “backup” in case the current relationship didn’t work out.

Overall, the researchers discovered that the women who were still in touch with their exes tended to have more difficulty adjusting to the split. They also reported higher levels of romantic feelings for their former partner, and felt less satisfied and committed in their current relationship. 

Perhaps unsurprisingly, the women’s current relationships were more likely to suffer if they were staying in touch with their ex as a “backup” option.

“If individuals perceive that they are heavily invested in the relationship and that there are few desirable alternatives to the relationship, they are likely to be more committed and satisfied,” write the authors of the study.

Read more: Women feel more pain after a breakup but are also more resilient 

“However, when other desirable alternatives to the current relationship are available, commitment may decrease, particularly given romantic (i.e., backup) motivations with the former romantic partner.”

If you want to stay friends with an ex-partner, you should examine why you want that, says Lindsey Rodriguez, assistant professor of psychology at the University of South Florida and lead researcher on the study. 

“Generally, this research shows that communication with former partners is not universally good or bad for current relationships. The important factor is why the person continues to communicate with the former partner,” Rodriguez tells Broadly.

“It is possible to continue to stay friends with an ex for purely platonic reasons, and that can be inconsequential or positive for the current relationship.”

However, she adds that maintaining contact with an ex can make it difficult to truly move on. “Many people find themselves ‘stuck’ on former partners or unable to really break away from the idea of a relationship with them,” she says. “When this happens, they experience higher rates of depression and anxiety, and are less likely to find themselves in a healthy new relationship.”

“As our research and previous work shows,” Rodriguez concludes, “there are real consequences for those who do continue to communicate, both for themselves and their new relationship.”