In the winter of 2004, women started arriving at Japanese hospitals complaining of chest pains and a shortness of breath. It was a month since a major earthquake had shaken the country, causing mudslides in the mountains, injuring 4,805 people and killing 68. In emergency rooms, doctors hooked the women up to ECG monitors, and saw the same extreme changes they’d expect with heart attacks. But subsequent tests showed their coronary arteries weren’t blocked, as they would be by a heart attack. Instead, their hearts had changed shape. It didn’t take long for these cases to be diagnosed as takotsubo cardiomyopathy, or “broken heart syndrome”.

Heartbreak is not simply a metaphor. Today, up to 7% of all sudden cardiac hospital admissions in Japan are diagnosed as takotsubo, when stress hormones after a traumatic event have caused a weakening of the left ventricle, meaning it can no longer pump effectively – for a while, it gives up. It hurts. And it clearly shows the link between the stresses happening in a person’s life, whether an earthquake or the end of a relationship, and their heart.

This understanding is one of the things that’s leading to heartbreak being taken seriously in a way it never has been before. There have been pop songs about heartbreak, of course. There have been novels and films and many thousands of poems, but now, after years of concentrating simplyon the process of falling in love, scientists are starting to look at the end of love, too. Today there are books that unpick the science of heartbreak and memoirs detailing the messy, sticky truth of it, and an “intensive care” retreat for heartbroken women to heal in a very nice hotel in the Peak District. All newly seeking to understand this slow torture. “Romance’s estranged cousin,” wrote Rachel Cusk in her 2012 divorce memoir, “a cruel character, all sleeplessness and adrenaline unsweetened by hope.”

Annie Lord’s heartbreak arrived one evening on Euston Road, London, when her boyfriend said he needed “to be alone”. Her memoir Notes on Heartbreak evolved from a long love letter she wrote to him afterwards, but never sent. To explore her pain, she returns to memories of the relationship, finding a kind of solace in the realisation that in order to get over her boyfriend she doesn’t have to forget him altogether. She remembers, she tells me, looking out of the window and finding it impossible to accept that most people she saw had gone through this agony. How was the world still functioning? In A Grief Observed, about the loss of his wife, CS Lewis says grief feels like suspense, “It comes from the frustration of so many impulses that had become habitual.” Reading that, Lord recognised the sensation: she was waiting for something that would never come. “For him to come around the corner asking where the towels were or to feel his leg hit me in bed . Knowing others had gone through something similar I felt less alone with my experiences.”

But it was reading about the science of heartbreak that had the biggest impact. “Saying, ‘I’m going through a breakup’ didn’t do what I was feeling justice. It felt too small, too ordinary.” So Lord sought out studies, learning things like, “The way your breathing adjusts to another person’s when you’re together for a long time, how in grief some people’s hearts really do break, or the fact that your brain craves that person the same way you would cocaine.”

Biological anthropologist Helen Fisher studied people who had been dumped and found the parts of the brain activated were those associated with addiction. A person rejected feels the same kinds of pain and craving they might with drugs and alcohol – they go through withdrawal and they can relapse, too, many months later, a midnight phone call, a stone at a window. “All of this helped me realise what I was feeling was justified. That I was going through something clinically awful.”

There have been hundreds of studies into the beginnings of love, but why has it taken so long for scientists to investigate its end, this “clinically awful” state? “Science has become more sophisticated at looking at transcription factors in our genome,” says writer Florence Williams. “We are used to relegating heartbreak to cultural melodrama, like popular songs and romantic poetry. But heartbreak isn’t just melodrama. It’s one of the most painful life experiences we have and we need to take it seriously for our mental and physical health.” When Williams’s husband left her after 25 years, she felt “imperilled”. She was plodding through her days, managing to feed her kids and occasionally meet her deadlines as a science journalist, but constantly falling ill, getting thin, unable to sleep. At 50, she’d never experienced anything like it, this “disorienting sorrow, shame and peril”. Not only did she want to figure out what heartbreak was doing to her body, she wanted to work out how to get better. Would she be among the 15% of people who don’t recover after a major breakup? She set to work.

“Heartbreak”, genomics researcher Steve Cole told her, “is one of the hidden landmines of human existence.” Concealed in the undergrowth of our relationships, it explodes at an unexpected moment, over dinner, at Christmas time, at a wedding, in bed. Among its documented effects, Williams found, are fragmented sleep, increased anxiety, poor impulse control, depression, cognitive decline, altered gene expression and early death. When this peculiar pain is studied, the findings are often as shocking and poetic as the art they inspire. For example, scan the brain of a heartbroken person and the same parts light up as somebody who has suffered a burn. Like the pain of returning to a fire, of reaching across a double bed and smelling smoke.

Williams was surprised by how dramatically the pain of heartbreak registers in our bodies. The feelings that come with heartbreak – grief, loneliness, anxiety – are acutely monitored by our nervous systems and our immune cells, which adjust to these emotions in preparation for confrontations and outcomes. “Our cells listen for loneliness,” she says. “That really blew me away. And it explains why people going through a big breakup face higher risk of early mortality and a number of diseases, particularly if they don’t work hard to process the pain.” To further discover how heartbreak impacts our brains, Williams interviewed a behavioural neuroscientist called Zoe Donaldson, who studies prairie voles. Prairie voles are even more committed to monogamy than humans, with around 75% staying together for life. In Donaldson’s heartbreak lab the voles live in boxes with their partners, “huddling” until one day when she parts them, hiding their lover behind a door. A certain grief sets in. How hard is the vole willing to work to be with its mate? And how long will it take for him to accept she is no longer there? One vole continued to press the lever to open the door for three hours and the researchers continued to monitor what was happening in its brain. Through a sensor implanted in the nucleus accumbens, a part of the brain associated with emotional learning and addiction, Donaldson can watch individual neurons firing. “The region is a sponge for the oxytocin and dopamine that get released during mating… and it likely encodes positive memories as well as the desire to repeat those memories,” writes Williams in her book, Heartbreak: A Personal and Scientific Journey. It also turns out to be one of the main areas of difference between prairie voles and their sluttier meadow vole cousins, who shun monogamy. The meadow voles don’t have many cell receptors for oxytocin in that region of their brain. Heartbroken humans, however, show plenty. In a human’s functional MRI scans, the nucleus accumbens is particularly active while looking at pictures of lost loved ones. “Basically, love boils down to this,” Williams concludes, “a strong emotion attached to memories.” Meadow voles enjoy mating, but memories of their lovers don’t carry the same emotional resonance. Heartbreak doesn’t touch them. (In our next lives, let us all come back as meadow voles.)

I wonder how it feels for Williams, for her identity to have become so entwined with heartbreak and the very worst moments of her life. She loves it, she says. “I love that I’ve been able to help so many people, that I’ve helped make big emotions something we can feel a little more comfortable with. I absolutely believe vulnerability leads to connection and growth.” Through going deep into heartbreak she has found, she tells me, “a sense of purpose”.

Psychologist Alice Haddon has discovered similar purpose, but she arrived there on a different journey. At the beginning of the pandemic Haddon’s mother died and in her grief she couldn’t find a route back to the way she’d worked for 20 years. She referred on her clients, and closed her practice. One morning she was listening to the radio, “a programme about romantic fraud and financial infidelity, when women are groomed or seduced online. A man had run off with this woman’s money and her voice came out of the radio, so distraught. And she just said, ‘I don’t know what to do, I don’t know where to go to get support.’ I was like…” and Haddon’s hands open and her eyes widen, “‘Oh!’” Soon after, she co-founded the Heartbreak Hotel in the Peak District.

When guests arrive there is cake waiting. Everybody puts their phones into a box and that evening they share their stories of heartbreak. Haddon has had guests who’ve been through financial betrayal, guests who’ve been left at the altar, guests whose husbands have left them for younger women or who have been seeing sex workers for years behind their backs. But from the following morning, through long walks and therapy sessions (including with an EMDR therapist specialising in PTSD – 30% of guests to the Heartbreak Hotel, Haddon claims, meet the criteria for PTSD when they arrive), there’s a moratorium on talking about the betrayer.

“Betrayal has a particular mechanism of rumination. It’s such a disorientating experience – something that was safe has become very dangerous,” Haddon explains. We ask ourselves questions, endless questions. When did it happen? Why didn’t I see it? Did I see it and choose to ignore it? “But that thinking process prevents us from feeling the pain of the loss and we know from a psychological point of view that’s what has to be felt in order to accept it’s happened. So we have to get the person who’s betrayed them out of the picture for the weekend.” For the rest of the weekend, the guests focus solely on themselves. There’s a lot of laughter, she says.

Heartbreak Hotel is only inviting women at the moment, because “there’s a particular context within which women sit and within which their betrayal happens”. These are usually mothers or carers, she says, “women in service to others, defined within a patriarchal structure. And so their internal sense of themselves is created within that context. When a betrayal happens, they haven’t checked in with themselves for a long time.” The “arc” of the programme is designed to take women away from their heartbreak, and into the next chapter of their life. “It’s about equivalent to six months of one-to-one therapy,” she says. “These women get to stay in their process, they get to witness it for each other.” And then later, in a WhatsApp group, they continue to look after each other.

“I’m very passionate,” Haddon says, a little self- consciously, “about getting women ‘back together with themselves’. You can’t take the betrayal away, you can’t take the pain away. But you can put somebody in a different position, where they can focus on themselves and support each other, and flourish.”

Through her research into the science of heartbreak, Williams tiptoed her way through the pain. “I divide the healing into three big categories: calming, connecting and finding purpose.” Spending time in nature was useful to her, as was therapy (both conventional and un-) and a happy rebound relationship. She also really liked getting off with a stranger under a tree in the moonlight. Later, on a psychedelic trip, she saw herself and her emotions as molecules, beads in a huge curtain, and emerged feeling less afraid of being alone. “Internally, I feel more in touch with my emotions, and because of that, more alive. I feel better able to cultivate beauty and awe and joy. I feel more empathic and I have deeper connections to the people in my life I care about. That is the great unexpected lesson – when we are lucky and we work at it – of heartbreak.”

As well as giving clarity to its horrors, a flake of solace to those tangled in bedsheets or crying on buses, the science behind heartbreak offers something else, something bigger. Falling in love cracks us open. It alters the brain permanently, making us more sensitive in ways that can bring both glee and misery. Those that are able to climb inside the grief and guts of heartbreak then dig their way out, whether using pop songs, therapy, science or patient friends, find themselves wiser, improved. Their stakes have risen. “My heart is scarred,” says Williams, “but it’s more open.”

Notes on Heartbreak by Annie Lord (guardianbookshop.com, £14.78); Heartbreak: A Personal and Scientific Journey by Florence Williams (guardianbookshop.com, £10.43). For details on the Heartbreak Hotel, go to theheartbreakhotel.co.uk

Body of evidence: the biology of heartbreak

• Heartbreak and rejection can trigger activity in the same area of the brain where physical pain is activated (the anterior insula and the anterior cingulate cortex)

• Corners of the brain that cause and respond to addiction can be activated by images or reminders of ex partners

• Some white blood cells monitor our moods, via our nervous system, and can listen out for heartbreak and loneliness, which in turn increases inflammation

• ‘Broken heart syndrome’ can cause the heart’s left ventricle to change shape and get larger, weakening its muscle, meaning it doesn’t pump blood as well as it should

• A breakup can lead to reduced levels of the feelgood neurochemicals dopamine and oxytocin, potentially causing withdrawal symptoms such as tremors, palpitations and even depression