Stephanie Ortigue of Syracuse University and colleagues worldwide conducted a meta-analysis that finds falling in love can take one-fifth of a second and then the brain starts to release euphoria-inducing chemicals such as dopamine, oxytocin, adrenaline and vasopressin, but the heart is involved as well.
"I would say the brain, but the heart is also related because the complex concept of love is formed by both bottom-up and top-down processes from the brain to the heart and vice versa," Ortigue says in a statement.
The analysis shows different parts of the brain are involved in love. For example, the unconditional love between a mother and a child include the middle of the brain, but passionate love is sparked by the reward part of the brain.
The meta-analysis also finds blood levels of nerve growth factor also increased when falling in love. This molecule plays an important role in the social chemistry of humans, or the phenomenon of "love at first sight," Ortigue says.
Conversely, when love goes wrong, it can cause significant emotional stress and depression.
The findings are published in the Journal of Sexual Medicine.