Is it normal to see apparitions?

Straight off, i'm not a druggie and have only done the whoopi weed a couple of times. About a year and a half ago i was with friends enjoying a few ales when i was offered a joint. I reluctently accepted and it effected me rather quickly. A few puffs and beers later i turned around to the upstairs deck to see an old lady smiling at me. After a few seconds i turned to my mate who owns the house and said she wont hurt you know. He said who? I replied the old lady in the corner. He went white and told me before he bought the house an old lady had passed away in her arm chair in that exact spot. In that instant i said well who is the boy with her? He nearly fell over and told me her Grandson had also died in the house a few years before! I can't explain it but it certainly made me believe there is something after death. It has never happened again after that night!