Religion

as well as a change in brain chemistry.

Here is just one study exploring this phenomenon.

The difference between this and a similar response in a worshiper is that the individual who have fallen in love with can be verified to actually exist (see the other excellent posts on this point).

https://www.sciencedaily.com/releases/2014/02/140206155244.htm

"Falling in love causes our body to release a flood of feel-good chemicals that trigger specific physical reactions," said Pat Mumby, PhD, co-director of the Loyola Sexual Wellness Clinic and professor, Department of Psychiatry & Behavioral Neurosciences, Loyola University Chicago Stritch School of Medicine (SSOM). "This internal elixir of love is responsible for making our cheeks flush, our palms sweat and our hearts race."

Levels of these substances, which include dopamine, adrenaline and norepinephrine, increase when two people fall in love. Dopamine creates feelings of euphoria while adrenaline and norepinephrine are responsible for the pitter-patter of the heart, restlessness and overall preoccupation that go along with experiencing love.

MRI scans indicate that love lights up the pleasure center of the brain. When we fall in love, blood flow increases in this area, which is the same part of the brain implicated in obsessive-compulsive behaviors.