This feature was first published in July 2025 in My Mensa Weekly, our exclusive newsletter for Mensa members. Find out more about becoming a Mensa member here.
Words: Claire Prentice
From our first day of nursery or school onwards, making new friends and sustaining friendships takes up time and emotional energy as well as being fun and fulfilling. Much research has been done on the negative effects of loneliness. However, in recent years, researchers have turned their attention to the science of friendship and the positive benefits it can bestow on mental and physical health, and even on prosperity.
Can you have too many friends?
Many people think that, when it comes to friends, the more the merrier, but research by Oxford academic Robin Dunbar on the maximum number of friendships people can sustain has become so influential that it has coined a phrase “Dunbar’s number.”
Dunbar’s research established that the number of friendships we can keep up with, without straining our cognitive limits or running out of time, is 150. Dunbar envisaged those 150 friends as broken down into levels according to the intimacy of the friendships. At the core of the friendship groups are five close friends – what Dunbar terms a “support clique” – with larger groups forming layers of connections, some of whom will be family members or acquaintances. The 150 number has been observed in diverse human societies, from tribes to online communities.
The benefits of a robust friendship network can be seen in more than just a good social life: the number and quality of close friends and family is now seen as the single best predictor of mental health, wellbeing and even longevity.
If sustaining 150 friendships seems a lot then you can take heart if you have a smaller friendship group. Even adding a few friends to your network can help your mental health. Research into 38,300 adults in 13 European countries showed that those with a smaller number of friends experienced a benefit to their mental health when their friendship group expanded, but for those with a large group to start with, adding more friends did not make an appreciable difference to mood or mental resilience.
Healthy mind, healthy body
There is an increasing body of evidence showing that friends can be good for physical health too. A study of more than 300,000 heart attack patients suggested that having a network of friends had a bigger impact on lowering the likelihood of having a second heart attack than stopping smoking.
Having a supportive network is also now recognised by diabetes experts as one of the key factors in helping patients stick to weight targets and self-care. Doctors believe that supportive friends keep morale up, and also provide accountability for decisions taken around weight, eating and drinking.
Animal friends
The rewards of friendship are great, so perhaps it’s no surprise that friendship isn’t confined to humans: animals make friends with other animals too. This has often been thought to bestow an evolutionary advantage – minimising competition for food or territory, adding to reproductive success or increasing infant survival.
Recent research on red squirrels, who are typically feisty and solitary, has shown that, despite their reputation as loners, they co-operate with their red squirrel neighbours, with benefits for their food supply.
So far, so Darwinian, but a growing body of evidence seems to show that animal friendships can be based on personality and affinity; what, in human terms, would be thought of as the pleasure of hanging out with people you get on with.
A study by researchers at the University of Hong Kong looked at water buffalo, who seem to make friends with other water buffalo with similar personalities. The research centred around a community of feral water buffalo living on Hong Kong’s Lantau Island, and their personalities were assessed on three measures; social tension, vigilance and general dominance. It was noted, for example, that the females with similar personalities spent more time grazing together.
The water buffalo research isn’t the first to identify personality as a factor in animal friendships. Chimpanzees and Assamese macaques like to spend time with partners who have similar personalities, and dolphins have been noted to associate socially with those who behave in the same way as they do.
The water buffalo researchers hope that their work will be able to point the way to better methods of conservation and animal management in future.
Give a friend a hand
When it comes to job hunting, everyone knows the saying: “It’s not what you know, it’s who you know.” Some businesses, such as LinkedIn, are even based around the idea that utilising the connections in your network is the best way to get a new job or find the perfect candidate to fill a vacancy. But can the right kind of social network help you get on in life?
A study published in Nature in 2022 explored the capacity that a social group has to improve the upward mobility of its members. The researchers examined 21 billion friendships on Facebook to study social capital – the strength of an individual’s social network and community – which has been identified in other studies (such as in education and health) as a powerful determinant of outcomes.
The good news, at least for those with successful friends, is that according to the researchers, economic mobility may be “facilitated by connections to people who can shape aspirations or provide access to information and job opportunities.”
It’s not a reason in itself to make friends but, given the multitude of benefits that friendship appears to bring, from physical health to mental resilience, maybe it’s time to get socialising!
Image credit: Shutterstock
