You can’t eat. You can’t sleep. Your stomach and heart flutter when this person contacts you or suggests spending time together. Sounds like all the telltale signs you may be falling in love.

But what happens in your brain when you begin to feel lovestruck? And how does the brain change over time when it comes to love?

“Love is a biological necessity—it’s as needed for our well-being as exercise, water, and food,” said neuroscientist Stephanie Cacioppo, PhD, author of Wired for Love: A Neuroscientist’s Journey Through Romance, Loss, and the Essence of Human Connection (Macmillan, 2022). “And from a neuroscientific viewpoint, we can really say that love blossoms in the brain.”

Two decades of research has shown that when it comes to early-stage intense romantic love—the kind we often think of when we talk about being lovestruck—a very primitive part of the brain’s reward system, located in the midbrain, is activated first, according to Lucy Brown, PhD, a neuroscientist and professor of neurology at Einstein College of Medicine in New York.

Brown and her lab partners used functional magnetic resonance imaging (fMRI) to study 10 women and seven men who were intensely “in love,” based on their scores on the passionate love scale, a 14-item questionnaire designed to assess the cognitive, emotional, and behavioral aspects of passionate love that relationship researchers have widely used for decades.

People who score in the highest range of this assessment are deemed as being wildly, even recklessly, in love. Those who score in the lowest range have admittedly lost their thrill for their partner.

Participants in Brown’s study alternately viewed a photograph of their beloved and a photograph of a familiar person. When viewing the photo of their romantic partner, participants experienced brain activation in the midbrain’s ventral tegmental area (VTA), which is the part of the brain connected to meeting basic needs such as drinking when we’re thirsty and eating when we’re hungry.

“It’s the area of the brain that controls things like swallowing and other basic reflexes,” Brown said. “While we often think about romantic love as this euphoric, amorphous thing and as a complex emotion, the activation we see in this very basic part of the brain is telling us that romantic love is actually a drive to fulfill a basic need.”

Additional fMRI studies conducted by Cacioppo shed more light on how love affects your brain. Her team found 12 areas of the brain work together to release chemicals such as the “feel-good” hormone dopamine, the “cuddle hormone” oxytocin, and adrenaline, which induces a euphoric sense of purpose. Her findings also indicated that the brain’s reward circuit—the amygdala, the hippocampus, and the prefrontal cortex—which is very sensitive to behaviors that induce pleasure, lit up on brain scans when talking about a loved one because of increased blood flow in these areas.

While all of this is happening, Cacioppo noted, our levels of serotonin—a key hormone in regulating appetite and intrusive anxious thoughts, drop. Low levels of serotonin are common among those with anxiety and obsessive-compulsive disorders.

“This explains why people in the early stages of love can become obsessed with small details, spending hours debating about a text to or from their beloved,” she said.