Strokes and hugs are being edged out of our lives, with doctors, teachers and colleagues increasingly hesitant about social touching. Is this hypervigilance of boundaries beginning to harm our mental health?

When did you last touch someone outside your family or intimate relationship? I don’t mean a brush of the fingers when you took your parcel from the delivery guy. I mean: when did you pat the arm or back of a stranger, colleague or friend? My own touch diary says that I have touched five people to whom I’m not related in the past seven days. One was a newborn and two were accidental (that was the delivery guy). Touch is the first sense humans develop in the womb, possessed even of 1.5cm embryos. But somewhere in adulthood what was instinctive to us as children has come to feel awkward, out of bounds.

In countless ways social touch is being nudged from our lives. In the UK, doctors were warned last month to avoid comforting patients with hugs lest they provoke legal action, and a government report found that foster carers were frightened to hug children in their care for the same reason. In the US the Girl Scouts caused a furore last December when it admonished parents for telling their daughters to hug relatives because “she doesn’t owe anyone a hug”. Teachers hesitate to touch pupils. And in the UK, in a loneliness epidemic, half a million older people go at least five days a week without seeing or touching a soul.

Sensing this deficit, a touch industry is burgeoning in Europe, Australia and the US, where professional cuddlers operate workshops, parties and one-to-one sessions to soothe the touch-deprived. At Cuddle Up To Me, a cuddle “retail centre” in Portland, Oregon, clients browse a 72-cuddle menu. Poses includes the Alligator, the Mamma Bear and, less appealingly, the Tarantino. In Japan, a “Tranquility chair” has been developed, its soft arms wrapping the sitter in a floppy embrace.

Is this what a crisis of touch looks like? And if so, what do humans risk losing, when we lose touch?

“Of course we are moving away from touch!” exclaims Francis McGlone, a professor in neuroscience at Liverpool John Moores university and a leader in the field of affective touch. He is worried. “We have demonised touch to a level at which it sparks off hysterical responses, it sparks off legislative processes, and this lack of touch is not good for mental health.” He has heard of teachers asking children to stick on a plaster themselves, rather than touch them and risk a complaint. “We seem to have been creating a touch-averse world,” he says. “It’s time to recover the social power of touch.”

Touch is commonly thought of as a single sense, but it is much more complex than that. Some nerve endings recognise itch, others vibration, pain, pressure and texture. And one exists solely to recognise a gentle stroking touch.

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Known as c tactile afferents, this last is the one that McGlone has studied for years. To find it, a needle is inserted into the skin to “fish”. “It’s like sitting on the banks of the river,” McGlone says. “One’s a pain fish. One’s an itch fish.” Hours can pass before anyone catches a gentle touch nerve, but this elusive fibre has helped to teach scientists why humans need touch.

By watching the nerve’s discharge behaviour while the skin is stroked, scientists have learned that the optimum speed of a human caress is 3cm to 5cm a second.

This may sound like a diverting snippet of touch trivia, but its application is far-reaching. When a parent strokes a child, for instance, “they are writing out the script that was laid down by 30 million years of evolution,” McGlone says. “We are destined to cuddle and stroke each other at predetermined velocities.” The pleasantness encourages us to keep touching, nourishes babies and binds adults, and threads wellbeing into the fabric of our being. It could also teach us more about the touch-averse, including how and when autism and eating disorders develop, and even lead us to a cure for loneliness.

Last year, researchers from University College London showed that slow, gentle stroking by a stranger reduced feelings of social exclusion.

“Bang on!” McGlone says. “This nerve fibre is responsible for so many aspects of our wellbeing across our lifespan. I call it the Higgs boson of the social brain. The missing particle that glues everything social together.” Ironically, having been brought up in the 50s, when parental affection was thought to encourage mawkish children, he is himself sensitive to touch, and feels a gentle stroke “like an electric shock”.

As a society, we instinctively understand the power of touch. That is why, after the tragic shooting at his school, the head of Marjory Stoneman Douglas in Florida promised “to hug each and every one” of his 3,300 students. A single, small touch can change countless lives. Princess Diana knew this when she held the hand of an Aids patient in 1987. So did Barack Obama when he stooped to let a young black boy pat his hair, so that he could feel his own potential in the palm of his hand.

Tiffany Field founded the Touch Research Institute at Miami Medical School to study this neglected sense and its impact on health. She enjoys a weekly massage and happily lists the positive effects of being touched. “We know from the science of what goes on under the skin that when the skin is moved, pressure receptors are stimulated,” she says. This “slows down heart rate, blood pressure and the release of cortisol”, which gives people better control over their stress hormones.

Being touched increases the number of natural killer cells, “the frontline of the immune system. Serotonin increases. That’s the body’s natural antidepressant. It enables deeper sleep,” Field says. Her appraisal is borne out by the experience of Kira “Cuddles” from Cuddle Up To Me in Portland, who has to remind her clients to check for phone, keys, wallet. “They leave with a dose of oxytocin. They are floating on a cloud.”

Most basically of all, touch tells us who we are. That is why in the womb, McGlone says, “with the amniotic fluid washing over it, the brain inside begins to realise, ‘I’ve got my body, and that’s somebody else’s.’ That developing brain has that sense of me rather than something else out there. If that doesn’t happen, you get this almost locked-in syndrome.”

Mary Carlson is 78. She worked as a student assistant with the legendary scientist Harry Harlow, whose experiments with monkeys found that the hankering for touch is so innate that an infant, removed from its mother, would cling to a cloth-covered wire surrogate rather than a cold wire one with milk. It would choose to feel nourished rather than be nourished.

Carlson met Harlow as a freshman. At the first lecture she attended, “he came out hooting and running around on all fours”. In his laboratory, she witnessed monkeys that as infants had been deprived of their mother’s touch. In social groups, they would “go off in a corner, self-grasping, staring into space.” She saw similar patterns of behaviour in humans three decades later when she visited orphanages in Romania, a legacy of Ceausescu’s regime, where tens of thousands of infants were raised with minimal human touch.

For Carlson, touch is “a sort of species recognition”. Which suggests that without touch, humans may be, well, less human.

“You just don’t see people touching each other these days,” Field complains. She has just come from a restaurant. “And everybody was on their cellphones.” At LaGuardia airport recently, she walked around the waiting area. “Not a soul was touching another. Even two-year-olds were sitting in carriages with iPads on their laps.” (Getting touch from their touch screens.) Then, at the Coconut Grove art festival, “There were people bumping into each other because it was so packed. I heard people say, ‘I’m sorry! Excuse me!’ and move off in a way that made it look like they were really embarrassed.”

Field is planning studies in restaurants and airports “to document how little touch there is and how much distraction by social media”. There is as yet no scientific data to connect declining touch to the rise of mobile technology or social media, but Field’s descriptions of people wrapped in their own worlds rather than each other, sitting in isolation, bowed over screens, a huddle unto themselves, are evocative and familiar.

Do those atomised people who bounce off each other at art fairs before spinning away in shame, or those who sit day after day alone in their homes carry shades of Harlow’s monkeys self-soothing in the corner of their cages? And if so, where will our loss of touch lead us?

Kellie Payne, research and policy manager at the Campaign to End Loneliness, says that loneliness is fatal precisely because it puts people “into a kind of defensive state where the levels of cortisol are raised. Having had negative experiences, they anticipate that their connection with people will also be negative,” which makes it hard to reinstate contact. To add to the challenge for the elderly, touch sensation is in decline. According to David J Linden, author of Touch: The Science of Hand, Heart and Mind, “Humans have their strongest touch sensation at around 20, after which it goes down by a percent a year for your whole life”.

Field, meanwhile, is worried about the rise in paediatric pain syndromes, such as irritable bowel syndrome and fibromyalgia, previously common only in adults. She thinks this is due to stress and the absence of touch, and is also worried that “kids are getting more and more aggressive because there is less and less touch”.

“This is what I’m concerned about,” McGlone says. “If this evolutionary system is in any way disturbed or interrupted, brains are good at finding compensation. It could be drugs or alcohol ... If you remove a reward system, the brain will try to find some other way to get that reward.”

Humans love touch. We love it so much that the word has the power to sell a heap of products from soft-touch pillows to velvet touch tights, expert touch saucepans and even smooth, perfecting touch face creams. But touching each other in an age of pervasive and historical sexual abuse and harassment no longer feels safe.

There is a hypervigilance of boundaries that makes it hard to find the right approach. “I think twice about hugging a colleague at work in a way that I didn’t a couple of years ago,” Linden says. “I’m thinking, maybe this is going to be misinterpreted. Maybe this is going to make somebody feel bad.”

Touch – even the gentlest kind processed by McGlone’s beloved c tactile afferents – is never only about affection, warmth and care, but also about power. (Just watch Donald Trump greet world leaders.) The so-called “Midas touch” studies which have shown that diners gently touched on the arm by their server will leave a generous tip, or that people in a care home eat more if touched, illustrate the power of touch to persuade. Touch can retract – as well as confer – agency. It is not a universal good. It can exacerbate the symptoms of those with autism, and those who have experienced trauma or abuse.

At her home in north London, I meet Anna Fortes Mayer, who has run Cuddle Workshop since 2010. We sit on her red sofa and talk about how to broach touch. She is not tactile, but then we are strangers and her sofa is large.

I tell her about my touch diary: by now my yoga teacher has patted me and I’ve collected a matchday hug from my daughter’s football coach. “It’s not much. It’s really not,” Fortes Mayer says, shaking her head. But what’s a person to do? How can we build more touch into our lives?

For a start, Fortes Mayer advises against “energetically leaning forward for a hug”. She dislikes the phrases “Do you want a hug?”, “Give us a hug” and “Can I have a hug?”; they are “all too, ‘Who takes ownership here?’” (This is the mistake Kesha made with Jerry Seinfeld.) She suggests instead, “Would you like to share a hug?”

Encouraging self-consciousness of the ways in which people offer and invite touch has many benefits. But this kind of touch can never be impulsive, immediate, if it comes with explanatory notes. And touch that breaks protocol can feel more affecting. Consider the excitement when Meghan Markle preferred a hug to a handshake, or Michelle Obama slipped an arm around the Queen’s back. Even McGlone, despite that 1950s upbringing, on a walk through the park, was tickled to see a “big rugby player type bloke” offer his wife and then him a hug. (He was so touched, he started to explain about c tactile afferents.)

In Fortes Mayer’s hall, I put my shoes back on and with my hands at my sides ask, “Anna, would you like to share a hug?” She says yes – and it feels good.

“I will often place my hand on someone’s shoulder,” Carlson says. “I believe in touch. There are ways you can do it so it isn’t demeaning.”

“Even stranger touch, when it’s wanted, is pretty good,” Linden points out. “Even petting your dog. Even petting a dog that’s not yours.” For the truly solitary, daily power walking stimulates pressure points. It’s what Tiffany Field does. She also advocates yoga: “It’s moving your limbs against each other.”

Of course, nobody thinks that a cure for loneliness will happen at a stroke, but maybe careful touch could bring it closer.