For some, eating alone can be a joyous thing: forking mouthfuls of pasta straight from the pan, peanut butter licked off a spoon, the unbridled pleasure of walking home from the chippie alone on a cold night. But regularly eating meals in isolation is a different story. This one factor is more strongly associated with unhappiness than any other apart from (unsurprisingly) having a mental illness. This is according to a new study by Oxford Economics that found, in a survey of 8,250 British adults, that people who always eat alone score 7.9 points lower, in terms of happiness, than the national average.

This research is far from the first to suggest a link between eating with others and happiness. Researchers at the University of Oxford last year found that the more that people eat with others, the more likely they are to feel happy and satisfied with their lives. The study also found that people who eat socially are more likely to feel better about themselves and have wider social and emotional support networks.

Robin Dunbar, a professor of psychology, worked on the Oxford University study. He says that “we simply don’t know” why people who eat together are happier. But it is clear that this is a regular social ritual, a moment of union and communion in our often chaotic lives. It can be a place of conversation, storytelling and closeness.

“At a psychological level, having friends just makes you happier,” says Dunbar. “The kinds of things that you do around the table with other people are very good at triggering the endorphin system, which is part of the brain’s pain-management system. Endorphins are opioids, they are chemically related to morphine – they are produced by the brain and give you an opiate high. That’s what you get when you do all this social stuff, including patting, cuddling and stroking. It is central to the way primates in general bond in their social groups and relationships.”

Our face-to-face relationships are, quite literally, a matter of life or death. “One of the biggest predictors of physical and mental health problems is loneliness,” says Dr Nick Lake, joint director for psychology and psychological therapy at Sussex Partnership NHS Foundation Trust. “That makes sense to people when they think of mental health. But the evidence is also clear that if you are someone who is lonely and isolated, your chance of suffering a major long-term condition such as coronary heart disease or cancer is also significantly increased, to the extent that it is almost as big a risk factor as smoking.”

One of the most striking pieces of evidence for this, says Dunbar, is a meta-analysis of 148 epidemiological studies that looked for the best predictors that patients would survive for 12 months after a heart attack. “The best two predictors, by a long way, are the number and quality of friends you have and giving up smoking,” he says. “You can eat as much as you like, you can slob about, you can drink as much alcohol as you like – the effect is very modest compared with these other two factors.”

Human beings are biologically engineered for human interaction – and particularly face-to-face interaction. One study from the University of Michigan found that replacing face-to-face contact with friends and family with messages on social media, emails or text messages could double our risk of depression. The study also found that those who made social contact with family and friends at least three times a week had the lowest level of depressive symptoms.

“We are the most social of all the animals,” says Prof Paul Gilbert, a psychologist and the founder of compassion-focused therapy. “Our brains and our bodies are built to be regulated through interactions with others from the day that we are born.” This is not the case with many creatures, such as turtles and fish, that procreate in vast numbers. “They don’t need looking after,” says Gilbert. “Many of them will die before they reach reproductive age. The caring behaviour [associated] with mammals is a major evolutionary adaptation – it changes the brain and the physiology of the body so that a parent is interested in staying close to an infant. One of the most important things is the human capacity for soothing and engaging. So, when a mother smiles at a baby and makes eye contact, that positive emotion in the face and the voice of the mother is stimulating positivity in the child. You can see why it’s called mirroring, the baby smiles back.

“The ability to stimulate positive emotions, which is linked to happiness, begins in interactions with others who are having positive emotions about you. So, when we see our friends and they say, ‘Good to see you’ – it’s important.”

But there are many factors that might prevent us from seeing friends and family: mental ill health, immobility, a lack of money. Alison Harris is a consultant clinical psychologist and professional lead for psychological services in Salford. “Austerity has a huge influence on the loss of happiness and wellbeing,” she says. “Homelessness and unemployment in particular takes us out of contact with others. In addition to the obvious harms of homelessness, it does massively increase social isolation and anxiety. To take that even further, many people are in exile from their communities. In mental health services, we see an enormous amount of grief, depression and anxiety in people who are asylum seekers and refugees and much of that is not just due to trauma or torture or detention or fleeing from their country, but from the severe rupture of being cut off from their families and communities of origin.”

When we are around others, it has an effect on our body. Some forms of friendship – going to parties, getting married, having positive interactions with others – stimulate our sympathetic nervous system. Gilbert says that the parasympathetic nervous system (otherwise known as the “rest and digest” system) “is stimulated through the verbal and voice tone of relations with each other. As far as we know, it’s not that stimulated through texts. Generally speaking, you’re designed to respond to voice tone and expression, and stroking. We are physiologically designed for face-to-face interaction.”

Of course, for those struggling with depression, the idea of physical contact can be impossible to fathom. At those moments, the capacity to lift up a mobile phone and type out a text is an enormous mark of progress. It may not be the ideal form of interaction, but it’s a vast improvement on staring at a wall.

Dragging ourselves out of low energy states – be that by trying to cultivate compassionate voices internally or having compassionate relationships with others – is key to Gilbert’s work. “If you ask someone, ‘What is your internal critic most frightened of?’ [you will find] it’s frightened of rejection, of being seen as no good. Of being unlovable, of not being wanted. All the raging that goes on beneath us, the thing that we fear most is shame – not being good enough or wanted. We are frightened of being revealed to be not so nice.”

He says that what has happened in the past decade, with the rise of social media, “is that it has become a very plastic society. We are all living like theatrical actors, presenting ourselves as our best. That can’t be real, and so we have many people who feel like failures or useless. They say: ‘I’m not as attractive as that, I’m overweight, I’m not kind or compassionate to others.’”

As Gilbert says, the best relationships are the ones where people love us for our perceived dark sides and flaws. “People forget that love is about loving you for the difficult things, not the easy things,” he says. It is those who know us intimately who can provide that, and they do it through their physical presence, through touch, and through eating, drinking and sharing with us. Spending time together is social nourishment. So, instead of texting a friend or messaging them on social media, why not knock on their door, look them in the eye and make yourselves both feel better?