Reflexive feeding

"Short- term? Moodiness, anger, violent behavior, paranoia. In the long term, they'll use up whatever reservoir of life energy they have. Once that happens, the Hunger pretty much takes over and makes them hunt."
"If they can't hunt?"
"They go insane."
"What about the people they feed on?" I asked.
"What about them?" Bob said. "They get little pieces of their life nibbled away. It does a form of spiritual damage, like when the Nightmare mauled Mickey Malone. It leaves them vulnerable to the Whites' mental allure and control, so it's easy for the Whites to come by for another bite."
"What happens if they keep getting fed on?"
"It's fed upon, o Bard, and if it keeps up the mortal burns out early. Sort of fades away into a kind of mindless daze. Heart attack during an intense feeding usually kills them."
"Killer sex," I said. "Literally."
"To die for," Bob confirmed.
An eerie thought, and one that disturbed me a lot more than I thought it should. "What if the vamp doesn't want to feed on someone?"
"Want doesn't matter," Bob said. "They feed on pure reflex. It's what they are."


Blood Rites Chapter 5, Page 38