It is commonly thought that sex can chemically bind the two partners.

“In humans, oxytocin is thought to be released during hugging, touching, and orgasm in both sexes. In the brain, oxytocin is involved in social recognition and bonding, and may be involved in the formation of trust between people and generosity.” “Bonding. In the Prairie Vole, oxytocin released into the brain of the female during sexual activity is important for forming a monogamous pair bond with her sexual partner. Vasopressin appears to have a similar effect in males. In people, plasma concentrations of oxytocin have been reported to be higher amongst people who claim to be falling in love.”  Quotes from Wikipedia entry:  Oxytocin

Prayer, I think, binds you to those people for whom you are praying.  You are taking an active interest in their lives, if you are praying in sincerity and not just saying words for the sake of saying words, but actually directing your will in your thoughts in supplication to the Lord for the benefit of another.  Not to say that there is some physiologic something that is going on, but when you bring another person’s interests before the Lord in a sincere and unselfish way, I think there is a relational connection made there.  Some type of grace.  Perhaps in recognition of your unselfish act, your gift of self, as it were, in that moment; perhaps as a help to foster relationships between people, for communion, as we are all called to communion with God and each other.

“Don’t you know that when you sleep with someone, your body makes a promise whether you do or not.”  From the movie “Vanilla Sky,” 2001.

 Take this as it is, my own late night musings, but it seems to me that as I pray for others, and especially as I pray repeatedly for them, I develop a connection with these people — a deep interest in their life and well-being.  And this draws me to want to know them more and to give more of myself out to them.  Which usually results in my praying for them even more.  This also seems to happen more when if you pray for them in secret or for a specific person whom you have not met.  Perhaps because in these ways, your prayer is more of a gift of self than if you are praying for one for whom you already care deeply.