Psychiatrists from Pavia University have associated early romantic love with a biochemical known as nerve growth factor (NGF). Apparently, levels of NGF in the bloodstream were significantly higher in subjects who were in the early stages of romance than individuals not in a relationship. Interestingly, "subjects in love who–after 12–24 months–maintained the same relationship but were no longer in the same mental state to which they had referred during the initial evaluation" did not have elevated NGF levels. Link to the paper summary in the journal Psychoneuroendocrinology, Link to Reuters article (Thanks, Gabe Adiv!)
David Pescovitz is Boing Boing's co-editor/managing partner. He's also a research director at Institute for the Future. On Instagram, he's @pesco.