Biochemistry of Love

Lately I had a few interesting discussions, initiated by a blog post, on the nature of feelings. Although I don't think of myself as a connaisseur, I've always tried to understand the physical rules of attraction. Being not a chemist nor a biologist, I am not "fully equiped" to conduct such an investigation, but I still try to understrand what's being done by people sharing this curiosity and who actually have these skills.
A very interesting research paper has been published by a team of italian scientists in a scientific publication called Psychoneuroendocrinology stating that there is a tight link between what we call "passion" (i.e. a very strong and quite compeling feeling toward a person), and a protein called NGF (Nerve Gowth Factor).
The team that authored this paper proceeded as following : they constituted 3 groups of a total of 58 people, both men and women, some of them having just met, and the others commiting in a longlasting relationship. They observed that "fresh" lovers had a much stronger NGF rate in their blood than the others, and that this rate declines gradually but inescapably in less than a year. Hence, the team's conclusion is crystal-clear : passion is predestined either to apathy or, in the best case, to fade into a more reasonable form of love, within a sole year!
I tend to consider that some people have developped an addiction to high rates of NGF, since they constantly look for passionate relationships which they live in much shorter cycles than the one predicted in the study! Maybe these people have a stronger "recovery" capacity, just like others emerge faster from deseases..
So, who thinks that love is biochemistry-driven?