Here's a couple of interesting reports on love and marriage. The first discusses a study in which marital strife was found to slow wound healing. The second reports on a study finding that a brain chemical called nerve growth factor increases when people fall in love, and the intensity of the feeling is related to the level of this chemical. Noone knows yet quite why that is, but it may have something to do with nerve growth factor releasing a hormone (vasopressin) that plays an important role in the formation of social bonding.