Biological researcher Helen Fisher’s 2005 fMRI study on couples in love found that romantic love is primarily a motivation system that can be similar to what we experience during addiction. Cognitive scientists at MIT explain that we experience peak processing and memory power at around age 18. We experience a lot of firsts (such as our first love) at a time when our brains are still developing or reaching this processing peak. These emotional and hormonal imprints of first love (at a time when our brains are in such an important growing stage or peak) cause life-long effects not only to our psyche but also to our biology.

2005 study by biological anthropologist Helen Fisher found that romantic love is primarily a motivation system, rather than an emotion (or set of emotions). Fisher and others have supported this finding by using fMRI (functional magnetic resonance imaging) to study the brains of people who are in love.

So, what happens in your brain when you fall in love? According to 2017 Harvard Medical School research:

Oxytocin, which is considered the “love hormone” responsible for our feelings of attachment and intimacy, is released.
Dopamine is released, which activates the reward pathway in our brain, causing a “motivation/reward” affect. This is where the “addiction” part of love comes in. We seek out the reward of love even through obstacles that may be dangerous or painful (a cheating spouse, etc.).
Norepinephrine, a hormone similar to dopamine, is also released in the initial stages of love (lust or infatuation) and this causes us to become giddy, energized, and euphoric.
During sex with a partner, cortisol levels lower. Cortisol is the primary “stress” hormone that is released in intense situations. Having less of this helps us ease into a more relaxed and vulnerable state, which is oftentimes why “meaningless sex” with someone turns into something more; you’re vulnerable and have just gotten a big dose of hormones that make you feel attached and infatuated.
Serotonin levels drop — this is important to note because the brains of people who have been diagnosed with obsessive-compulsive disorder (OCD) also have lower serotonin levels. This leads to speculation that being in love can make you act with obsessive-compulsive tendencies.
The results of the Harvard study (combined with Fisher’s fMRI study on a brain in love) very strongly suggest that because love provides a kind of chemical feedback in our brains, recreating this chemical response may eventually become our human drive or motivation to stay in love.

Our first loves take longer to heal
With this evidence in mind, we can recall what it felt like to be in love for the first time and to experience all of these hormone surges — only to have that taken away when the relationship ends.

Heartbreak is a complex and emotional thing — but there is no heartbreak that hits you quite like the first time. According to a 2017 study from the Journal of Positive Psychology, 71% of people are able to heal from a breakup within a span of three months after the relationship has ended. In this context, “healing” meant the participants in the study reported feeling “rediscovery of self” and “more positive emotions.”

Of course, some feelings of sadness, anger, resentment, and pain may linger on for a while longer. But typically, you’re able to see past your heartache and into what else life has to offer within three months of a relationship ending.

Why is it, then, that our first love seems to hold on for longer?
While research on this specific topic is quite thin, we can speculate the real reason by looking at what we know about what our brains experience when we fall in love. The first time you fell in love, your brain experienced all the things mentioned above (increases in positive hormones, decreases in negative hormones).

Multiple studies have confirmed our brains experience something very much like an addiction when we’re in love. The first time may be the most important because it’s the foundation. Most likely, you experienced this foundation of love during a time (adolescence) when your brain was still developing.

While we may be triggered to think of our first love in an emotional way when we hear a certain song or see a photo of them on social media, it’s the hormonal imprints that cause the life-long effects we all experience. The hormonal interactions are imprinted in the sensory areas of the brain at a time when the neurological developments we are experiencing are forming who we are as individuals.

Jefferson Singer, a psychologist who focuses on autobiographical memory, says that most people experience a “memory bump” between the ages of 15 and 26. This memory bump happens at a time when we are experiencing all kinds of firsts (driving a car, having sex, falling in love, etc.). Later in life, these memories tend to be more impactful because they occurred when our memory was at its peak.

“We have the opportunity to rehearse it and replay it, rethink it, reimagine it, re-experience it,” says Singer.

This idea is corroborated by cognitive scientists at MIT, who explained that the overall brain processing power and detail memory peak for our brains happens around 18 years old.

First love also affects us psychologically. According to Dr. Niloo Dardashti, a couples therapist based in New York, the feelings we experience with our first love become a blueprint for how we approach future relationships. In a very real way, just as our perception of platonic and familial love is forged in childhood by our parents or caregivers, our idea of romantic love is impacted by how we experience it for the first time.

There is still be much research to be done on the true effects of love on the human brain, but from what we understand so far, love doesn’t just affect us while we experience it. Its impact on our biology can be felt for the rest of our lives, and the power of this phenomenon can be difficult to explain and understand, as Albert Einstein once put it: “How on earth are you going to explain in terms of chemistry and physics so important a biological phenomenon as first love?”

This article was originally published in October 2020. It was updated in March 2022.