A few years ago I was at my university’s library, frantically refreshing a dating app. Under my crush’s photo there was a location setting that told me how far she was from me. “One mile away!” I felt a surge of adrenaline and my mind started racing.

I was a promoter for a gay nightclub in London’s Soho, which was where I met Lucy. I’d drop my flyers on purpose and she’d help me pick them up. We had been on a few dates and were making plans to meet again. Then we came across each other on a dating app – “Fancy seeing you here!” – and matched as a joke. Even though dating apps were probably unreliable in their geolocation abilities, suddenly I could gauge her distance from me.

I hatched a harebrained plot to run to Soho, where I guessed Lucy was out with friends. Maybe we would bump into each other. My friends cheered me on, working out how long it would take to jog there.

By the time I got to town, I refreshed the app, and sure enough, “13 miles away”. She was gone. On the tube going home, I wretchedly asked myself: “Why did I do that? What is going on with me?”

My crush on Lucy escalated quickly. I was lovesick for the first time in my life. I couldn’t concentrate on university or work because I was consumed by thoughts of her. In the middle of the night I would stare forlornly at her “last seen at 18.57” status. She had not replied to my message. Silently, suddenly the status would change to “online”. I would be simultaneously overjoyed and crestfallen: she was finally available, but not talking to me.

Too embarrassed to tell my friends how distraught I was, in an attempt to understand what I was going through I went online and typed in “love”, “agony” and “lovesickness”. I came across the term “limerence”, coined by psychologist Dorothy Tennov in her 1979 book Love and Limerence: The Experience of Being in Love.

It isn’t very romantic, but her research suggests that limerence is caused by biochemical processes that happen in the brain. A cocktail of norepinephrine, dopamine, phenylethylamine, oestrogen and testosterone makes you feel euphoric when you fall in limerence. Tennov compares the experience to the intensity an addict feels in the all-consuming pull for drugs: limerent people find themselves doing bizarre things in order to pursue their crush.

So how is limerence different from normal heartache?

For a start, it’s more extreme. I felt sure this agony was more than a usual crush because of how it was affecting my mental health. Dr Amy Chung, a psychiatry registrar for the East London NHS Foundation Trust, suggests that lovesickness might become pathological depending on the severity and distress caused: “In general, something becomes that way if it is impacting someone’s daily life and function.”

Dr Richard Taylor from University College London is a forensic psychiatrist who has treated patients suffering from pathological love states. He theorises that limerence is like post-traumatic stress disorder in reverse. “Instead of stress, it’s ecstasy. In PTSD you get intense re-experiencing via flashbacks dreams, intrusive thoughts, accompanied with hypervigilance and anxiety,” he explains. “But with lovesickness, stress is substituted with feelings of love.”

On the internet, limerence has been popularised with self-help books and confidence coaches who talk about it as something that you can “get over” with some effort. There are chatrooms and websites devoted to limerence, full of hopeful, anguished people looking for answers. The blog Living With Limerence receives 10,000-15,000 visitors a month. The users speak fluently with acronyms like EA (emotional affair) and LO (limerence object).

Whenever my friends tell me about having a crush, I’m always sympathetic because I remember the trouble I went through with Lucy and how it impacted my mental health. Once, I was with my friend Melvin when he suddenly burst into tears. He told me that months before, at a dinner, someone held out a chair for him, and he kept replaying the moment in his mind: “Does this mean they like me?”

I was astonished. My brilliant, capable friend was going through this as well. If limerence is considered a mental health issue, Dr Chung says that can affect anybody regardless of their race, age or sexuality: “Some people might be more at risk, depending on things like coexisting mental illness, history of trauma, poor social network, unemployment, low socio-economic status, drug and alcohol abuse, family history of mental illness.”

Later, in a Reddit group for limerence, I meet Jade. She is in her mid-30s, has been married for 15 years and has never been tempted with infidelity, until now. She met Jun through online gaming. They’ve not met in person, but they might once the pandemic has eased.

“He totally consumes my day,” Jade says. “I think about him when I wake up and until I fall asleep.” She constantly checks to see if he has messaged her. “Today was the longest stretch that he hadn’t texted me. I was anxious all day. He finally texted me and I was so relieved and happy. I hate that my mood is dependent on whether or not I hear from him.”

Jade finds herself daydreaming about him. “It’s mostly about the memories we’ve made together. Like the things he’s said to me and the way he looked at me on a video call.” She wants these feelings to stop: “I’m impatient with my child, slacking with my responsibilities as a wife and mother – my spouse and son can tell, but they don’t know what’s going on.”

Jun knows that Jade is torn between intense feelings for him and her marriage, but she hasn’t mentioned limerence to him. “I feel like it’s this dirty little secret.” Dr Taylor suggests there is an understandable stigma to any “medicalisation” of a mental state that is essentially on the spectrum of normal human experience.” Popular culture has also romanticised this toll on our mental health as part of falling in love. In almost every romcom, the protagonist will struggle in a romantic montage backed with sad music: they can’t sleep, will wait by the phone, and are distracted in their relationships with the family and friends.

Lockdowns mean meeting new people and dating has been happening online – remotely. When not communicating in person, nuances of body language and facial expressions get lost. Jade muses that because she only gets text messages and video calls from Jun, there’s empty space into which she can project her romantic reveries. Recently, he made asinine jokes which brought her sharply back to reality: “Whenever I interact with him, my limerence is less intense. It’s my own fantasies that draw me in.”

Tennov suggests that limerence can last a few weeks to several decades, the average ranging from 18 months to three years. The length can depend on whether feelings are reciprocated, which can make limerence linger. What makes limerence worse is if the other person gives you mixed signals, or there’s some physical or emotional obstacle such as geographical distance, or if they’re already in a relationship. These uncertainties can perpetuate the fervour and ferocity of emotions.

I got over my limerence after a few weeks. Life happened, priorities shifted, and I began to get my focus back. It all feels like a bad dream. I’m grateful Lucy never texted me back, and wonder if she knew what I was going through. To this day, we haven’t spoken about it. Becoming aware of the concept helped me move on, and made it easier to recognise the signs – saving me from falling headfirst in limerence again.

Five signs you’re in limerence

1 Idealising the person’s characteristics, whether they are good or bad.

2 Despair at rejection, and euphoria at perceived signs of reciprocation.

3 Intrusive thoughts, including fantasising about imaginary scenarios; being reminded of the person everywhere; and obsessively replaying and dissecting encounters with them.

4 Arranging your schedule to increase possible encounters with them.

5 Extreme shyness, and physical symptoms like “butterflies” around them.

Some names have been changed