My experience with people who believe they are troubled with unseen entities is that a majority of the time...the vast majority...these occurrences are caused by a psychological out-picturing of aspects of the individual experiencing the phenomenon that are not integrated into the personality. Usually the person in question is pessimistic and has low self-esteem, they are always the victim and claim "they" (that is, other people around them) did it "to them" in most of daily life interaction. This personality profile sets up a fertile atmosphere that needs only to be provided with an emotional charge (which teenagers have an abundance of, as I remember) to create phenomena. I have found that if I can psychologically get the person to integrate aspects of themselves, become positive in their thinking and self-confident, then these apparitions are dispersed.
Another thing to note about poltergeist phenomena in a home is that although the teenager may be the catalyst for the paranormal events, the people who live with the teenager feed the energy of the phenomena by adding their fears, anxiety and emotional tension. Thus, the entire family is involved in the amplification of the emotionally charged psychic energy the teenager is broadcasting. Therefore when these situations arise, all members of the household must work on resolving their personality reactions and be responsible by maintaining a calm, centered and positive attitude. Stress amplifies the energy needed for phenomenon of this sort to occur.
A very small portion of these reports (less than 1%) actually do have to do with entities that are separate from the person experiencing the phenomenon.
There are many ways in which these entities can manifest themselves, positively and negatively. A lot has to do, again, with the psychology of the person(s) involved as to what they attract into their presence..."negative entities" seem to be unable to, or uninterested in, disturbing or harassing a positive, self-confident person who firmly takes responsibility for their Spiritual growth and well-being.
Each individual has the power to say no. This is as true on inner dimensions and etheric dimensions as it is in the "real" world. If one uses their internal sword of discernment, and stands firmly saying "no" to anything that one feels is inappropriate, they will be fine. When one fears things...anything...they give up their ability to say no; they give their power to another person or entity and place themselves in the role of victim. Whether it is an abusive person in your life, or an unpleasant entity...YOU have the ultimate power, authority, and responsibility to accept or reject its presence in your reality."