Not trying to be an asshole here...But hallucinations tend to be symptom of a psychotic process (i.e., schizophrenia, can occur during mania, depression, etc.). It can be treated. I don't presonally believe in any sort of spirits, so my opinion's biased anyway.
"Brother, you better get down on your knees and pay...a thousand more fools are being born every f***ing day" -Bad Religion