Are there ghosts - or just an over developed imagination?

For the past 5 or so years I have been working in the aged care industry as a nurse and have heard many stories from colleagues who have seen ghosts or had unusual experiences while working on night shift. 

Buzzers going off in empty rooms, electronic doors opening and closing by themselves, lifts operating with no one inside them to name a few I have personally experienced. 

Is it ghosts? - I don't know and there could be a dozen explainations, electrical faults, wind, imagination, people playing practical jokes -- or perhaps the spirits of the many souls who have lived, loved and died within the walls of the  home and somehow left behind the imprint of their existence.

Most of the time this doesn't bother me too much as I do believe the living can do us more harm than the departed, still on the odd occasion I have felt very uncomfortable for no apparent reason and had to leave an area because of this, and other times have felt an overwhelming sense of love that I can't explain.

Perhaps this doesn't answer the question if ghosts exist or not, I am a strong believer in energy, and the power of the mind, perhaps it's just one of those things - if you believe, they are real, if you don't then nothing will prove it to you. I prefer to keep an open mind and a healthy respect --- just in case!