When you first fall in love, you are not experiencing an emotion, but a motivation or drive, new brain scanning studies have shown.
The early stages of a romantic relationship spark activity in dopamine-rich brain regions associated with motivation and reward. The more intense the relationship is, the greater the activity.
Here is the best part, or I suppose I should say the worst part:
Early on in a relationship, the images showed that the brain seems to be very focused on planning and pursuit of pleasurable reward, says Fisher, mediated by regions called the right caudate nucleus and right ventral tegmentum. The same regions become active when a person enjoys the pleasure of eating chocolate, she adds…There are also patterns that resemble aspects of obsessive compulsive disorder.
Here is the story from New Scientist, here is related research on the links between love and OCD. The research also suggests gender differences; male love has more to do with lust than does female love.