Around half of our acquaintances may be “frenemies” – and they could have a surprising impact on your psychology and physical well-being, says David Robson.

I have a problem. I have friends that I love to hate. My “frenemies”, as they are known. And they could be affecting my health.

Don’t get me wrong: I love these people. It’s just they drive me crazy. The worst was vain, delusional, and peppered every conversation with barely concealed insults. He would ask me about my news, only to start yawning exaggeratedly. “Boring!” he would then interject, in a fake Valley Girl accent (on the West Coast this may be acceptable, but this was in London).

It sounds trite, but this would leave me seething for days. Yet when, after years of frustration, I’d plucked up the courage to cool things, I was left with a perverse feeling of guilt and remorse, over all the good that is beginning to slip away too. When I wasn’t the butt of his jokes, he could be pretty funny.

I’ve discovered these friendships are beginning to attract serious attention from psychologists. They even have a technical term for it – “ambivalent relationships”. According to Julianne Holt-Lunstad at Brigham Young University in Utah, on average about half of our social network consists of people we both love and hate. “It is rare to encounter someone who doesn’t have at least one ambivalent relationship,” she says.

And that might be a more serious concern than it first appears. Holt-Lunstad’s work suggests that “frenemies” could be far more damaging than the people you actively, unambiguously hate; they might even damage your well-being and put your health at risk. So why do we continue to maintain these toxic friendships?

Support network

To understand this we need to look at the impact our social networks can have. For the most part, a lively mix of friends and acquaintances was thought to be protective. Analysing 150 published studies, Holt-Lunstad found that strong social ties reduce your risk of death to about the same extent as quitting smoking. Being lonely was about twice as harmful as being obese.

How come? Friends are meant to help us to relax and protect us from stress. Stress raises blood pressure, and ramps up the release of inflammatory molecules that could increase the risk of a whole host of ailments – whereas friends can help to soothe some of these responses. Conversely, the unhappiness of loneliness can itself amplify many of these processes and lead to other complications, like sleep-loss.

There are many shades of friendship, however. As Robin Dunbar at the University of Oxford (the man behind Dunbar’s number) points out, fickle friends are part and parcel of our evolution in large social groups. “You are always dealing with a set of competing interests. The problem is how to neutralise those stresses to allow the group to remain coherent through time,” he says. “So you need to be prepared to butter up your allies, which will also include your frenemies. You are tolerating them in order to manage them better.” The instinct to keep our friends close, and our frenemies closer, seems to have stuck.

Unfortunately, the earlier studies examining our friends’ influence on our health had not looked at these nuances. So Holt-Lunstad and Bert Uchino at the University of Utah explored whether the good traits of a frenemy outweigh the bad. They were shocked by what they discovered.

Under pressure

In one of their first studies they worked out the volunteer’s networks of mid-to long friendships through questionnaires, and then fixed them with blood pressure monitors before sending the volunteers back into the real world for a couple of days. “Any time they interacted with anyone, we got a blood pressure reading,” says Holt-Lunstad. As you might expect, blood pressure was lower when people mixed with their supportive friends, compared to their “aversive” acquaintances – be it an insulting co-worker or moody boss. But the big surprise was that their blood pressure rose highest of all when they were with their ambivalent friends.

Later experiments only confirmed and extended the findings. “Even when the other person is just in another room in the lab, they have higher blood pressure and higher levels of anxiety,” says Holt-Lunstad. “It’s just the anticipation of having to interact with them.” Least expected of all, priming participants with a subliminal cue (flashing the frenemy’s name on a screen) seemed to increase measures of stress, such as heart rate. “It suggests that our relationships have an impact not just direct interactions, but through these less consciously perceived processes that operating all the time in everyday life,” says Uchino. Anything that reminds you of them could be triggering these responses in your body.

In this way, frenemies seem to be among the most stressful people we encounter. Partly, that’s down to their unreliability. “There’s this uncertainty,” says Holt-Lunstad. “Are they going to come through for me or bring up a painful topic again?” she adds. Uchino agrees, and suggests our close lasting ties can make them even more hurtful than the people we may try to actively avoid. “They are almost part of our self,” he says. “So what they do and say can have a much bigger effect on us. And because, emotionally you have a stronger connection, they have a stronger opportunity to hurt.” He thinks that you would actually find it easier to dismiss the slights of a known enemy, since they mean less to us. “And that’s not just in the moment; you tend to ruminate on their hurtful conversations for longer periods of time,” says Uchino.

Breaking ties

For now, Uchino and Holt-Lunstad’s studies have most looked at the short-term influence of frenemies, and they would now like to investigate how they add up over years and decades. Unfortunately, few of the longitudinal studies so far have collected data on the particular qualities of people’s relationships – but Uchino has some early, though circumstantial, evidence from damage in the volunteers’ DNA. Each chromosome on our cell is capped by a length of DNA called “telomeres”. As we age, our telomeres tend to dwindle – leaving a cell open to a range of problems, including cancerous growth. For this reason, telomere length is often used as a measure of cellular ageing – and it is known to be influenced by stress. Uchino found that people with more ambivalent friends also had shorter telomeres.

If that bears out with further studies, we may all need to reconsider our relationships and whether they are worth the upset they bring. Unfortunately, it’s not always easy to prune these people from your social network – especially considering the fact that they are often lifelong friendships. When Holt-Lunstad and Uchino questioned people about the reasons that they stayed in touch with their frenemies, many talked about a sense of loyalty. “We feel a sense of commitment because we’ve known them for many years,” says Holt-Lunstad. Others wanted to take the moral high-ground. “There’s the perception that you ought to turn the other cheek, be the bigger person.”

Knowing this, how do they recommend dealing with frenemies? Uchino’s personal strategy is to talk to his frenemies and explain his issues – in the hope of reaching a mutual understanding. “When you look at how people cope with their ambivalent ties, there’s not a lot of direct coping like that – often we lie to them, ignore them or simply avoid them.” He’s also looking into the possibility that meditation could be a good coping mechanism. A few studies have found that regularly meditating on your acquaintances’ – even your frenemies’ – good points can improve psychological well-being and health. But Uchino points out the trials have mostly been small and poorly controlled, so he would like to build more robust studies.

When it comes to my own friendships, one of Uchino’s comments sticks in my mind. “We’re all busy and don’t pick up on cues that people need support, which may lead to positive and negative feelings,” he says. It’s not something I’m proud to admit, but I’m guilty as charged. By setting myself on a pedestal, I may be my own worst frenemy.

If you would like to comment on this article, or anything else you have seen on Future, head over to our Facebook or Google+ page, or message us on Twitter.