Here is an interesting description of Psychic Vampirism. I've included several good links for more in-depth reading about the phenomena:
While they may not suck the blood out of you, they do drain your energies leaving you depressed and irritable say Wiccans.
If you've ever been in a crowded train or party and come back home feeling physically sick, angry, cranky, or irritable for no reason, you were probably subjected to an attack from a psychic vampire according to Sangeeta Krishnan, High Priestess, Maya Wicca Tradition.
How to identify a 'psychic vampire'?
Shahrukh Vazir, a tarot reader, says, "People associate the word vampire with blood sucking creatures, however the concept of a 'psychic vampire' is slightly different because they do not suck your blood but drain you of your psychic energy. You can come across a psychic vampire anywhere - a screaming baby that makes you irritable, a crowded train, a walk in the hot sun. But if there is a problem, there is a solution to it. There are ways to protect oneself from this loss of energy. To start off, we should be aware that one is loosing psychic energy. Next, it is important to want to retain this energy. This intention is enough to shield oneself."
How spiritual healing can protect you?
Sangeeta adds, "Not everyone is vulnerable to a psychic attack. If you are well grounded, and your 'spiritual immunity' is high, you will be protected from all kinds of psychic attacks. If you identify a place or person that drains your energy (whether or not it is unintentional or malicious), the simplest way to deal with it in the short term is by staying away from the person/place/object. You can also visualise a bright, golden sphere surrounding your body that diverts all negative energy. One very simple way of protection is salt. Salt crystals are powerful protectors of energy and one of the best ways to protect yourself using salt is to put a fistful of pure, uniodised sea salt in your bath water. Crystals like obsidian and tourmaline can be placed at a spot or carried around as they absorb negative energy. Smudging a house (or yourself) with dhoop or smoke of frankincense is another way to energise and strengthen your auric field and prevent psychic attacks."
Mandaar Naik, a tarot reader believes in the power of spiritual healing and faith. He says, "Every living body in the universe is surrounded by invisible energy, which we often refer to as an 'aura'. It's channelised with each other, knowingly or unknowingly. All of us draw energy from each other, as well as send it. However, there are some people who are knowingly or unknowingly drawing energies from other people. Such individuals are like 'energy/psychic vampires'. To avoid becoming a victim, one can turn to Reiki, chanting mantras and practicing meditation. You can also use tantras eg. Shiv-Swar shastra are tools to shield one self from such people."
Read Michelle Belanger's online edition of the Psychic Vampire Codex or buy it The Psychic Vampire Codex: A Manual of Magick and Energy Work - Other good sources are The Demoniacal: Psychic Vampire and The Empath & The Psychic Vampire...Lon
Psychic Vampires: Protection from Energy Predators & Parasites
The Psychic Vampires Guide: To Subtle Body Language and Psionics
The Psychic Energy Codex: A Manual For Developing Your Subtle Senses