I think it seems quite reasonable. I know when I have been very depressed and tired I "see things" out of the corner of my eye all the time, flashes of movement etc. I did wonder if I was really seeing spirits etc. Im not so sure now, I think it was probably due to my state if mind. I would have demonic dreams of possession as well. This was how I came to know that I was getting depressed again and knew to get help. My counsellor thinks it's a warning system my body has developed. I'm inclined to agree, but sometimes I'm so sure something was there.
However if you speak to my mother she really believes there is something out there and has apparently experienced things. The weird thing is both me, mum and my Gran do seem to have a certain "knowing" about us. Like we always know when something is wrong or will be thinking about a person and they will suddenly phone etc. My sister definitely doesn't have this. One time my mum was telling me she has a spirit guide I was just about to ask what he was called when the name David just came into my head and yep he was called David!
Basically I don't know! Maybe some people do have sixth sense? I sound like a right freak now!!