"When you're in the throes of this romantic love it's overwhelming, you're out of control, you're irrational," researcher Helen Fisher of Rutgers University, New Brunswick, N.J., told the New York Times.
"When rejected, some people contemplate stalking, homicide, suicide. This drive for romantic love can be stronger than the will to live," Fisher said.
She and other researchers, reporting in The Journal of Neurophysiology, used functional magnetic resonance imaging to generate 2,500 brain scans of 17 recently in-love college students.
They measured neural responses to pictures of each student's love interest and an acquaintance. People in love had greater activity in the brain area that makes or receives dopamine, which increases when people desire or wish for a reward.
Separate parts of the brain control sexual arousal and long-term commitment, researchers said.