Any scientist will tell you that there is no way one human body can leech energy from another over any distance. Even static electricity can only jump a distance of millimeters between bodies.
There are no real "psychic vampires". It is nothing more than a self-induced, self-perpetuating delusion, and is classified as a delusion of grandeur, with overtones of the victim or martyr.
"Psychic vampires" cannot drain anyone of anything - it is a autonomic response triggered by a biofeedback mechanism. They truly believe that they can do this, and believe it so strongly, that their bodies release a wave of adrenaline and endorphins, resulting in the "feel good high" they claim to feel, and the adrenaline boost is responsible for the physical "augmentation" of strength and speed some report.
As with any high, they eventually come down, resulting in a period of feeling tired, sluggish, etc. until the next time they "feed" - which is a delusion, but their bodies release the endorphins anyway. Not understanding the actual way their bodies work, these people rationalize that they are therefore "psychic vampires" in order to feed their egos and bolster their sense of confidence and self-worth. They claim this "awakening" happens during puberty, and that they spontaneously develop a "lack of energy". Funny how that coincides with teen angst, rebellion, searching for self, etc. and all the phases of the developing Id and Ego.
As for their "donors", once again the response these people report to a "feeding" is in line with a sympathetic response brought on by their delusion that they have been "fed upon". A good analogy here is how some husbands report sympathetic labor pains when their wife is about to deliver. It is real to them, but the source is in their own bodies - not because they are empathically "transferring" some of their wife's pain to themselves.
I encountered a self-professed "psychic vampire" in the hospital during my clinicals. He had wrecked an ATV, and his leg was broken in multiple places. He claimed he was "taking energy" from everyone around him in order to heal faster, and that when I got home I would probably be "really tired". I went home after eight hours, went out and did 7 miles on my kayak, and bicycled 6. Slept normally, and woke up well rested. As for him, he attempted soon thereafter to get up and go to the restroom by himself because he was "healed" well enough. The idiot rebroke his femur as soon as he put weight on it. He eventually did make it home, but friends of mine on that floor said it took him longer to heal than normal.
The human body only generates three quantifiable forms of energy:
1. Neurological (electrical brain and nerve signals) which travels along nervous pathways insulated in deep tissue. If this is the energy "psi" vamps claim to use, then their "victims" would collapse in a manner similiar to a neurological stroke as the electrical pulses were drained. In all likelihood they would die, because these signals also control autonomic responses such as the breathing reflex and your heartbeat. If this is the energy they claim to need, why not just carry around a few D-cell batteries?
2. Electromagnetic, generated in tandem with your neurological output. Every living thing has an EM field. The idea that you could "drain" or feed from it is ridiculous. All EM fields are in constant flux. So-called "psi" vampires point to Kirlian photography, which is EM sensitive, as proof that draining can occur. All EM fields interact and are in constant change. Regardless of what anyone tells you, Kirlian cannot provide scientific, empirical data. If this is the energy they need, it would be easier to carry around several magnets, as their fields will overlap yours and strengthen it.
3. Caloric, or heat energy. If this energy is what the vampires need, then a draining would leave you cold and shivering, and probably hypothermic and hypoglycemic. If this is the energy they need, it would be much simpler to eat a sandwich and put on a sweater.
If anyone claims that "psy vamps" are real, fine. Here's a challenge: find a policeman and drain him to the point where he is so tired he can no longer stand or resist, make off with his gun, badge, and nightsick - and do it on video with no stops, edits, pauses, or lookaways.
As for "psychics" - there is not one single shred of verified psychic ability. They can occasionally make good guesses, and then pass it off as their "ability", but no claim of psionics, psychokinesis, telekinesis, divination, etc. etc. ad nauseum has ever been independently confirmed by third party experts using the scientific process.
I'm a Nurse, real education, real experience.