An experience involving the apparent perception of something not really present. Horrific hallucinations after drug use or even without drugs that lead to depression . Ghosts after use of LSD or High on cocaine or heroin. Look, seen many cases like that and experienced personally. Consulted with doctors , Tried mood stabilizers , studied hard and found the reason in Vedic Astrology. Ghosts really don’t exist. A person sees these things in the third and fourth dimension. Those negative energies and illusions that really don’t exist. Rahu does that. Rahu in the 12th house with moon or with sun . Sun is the soul and connection with the the father and moon is the mind of the person. Moon signifies motherly figures too. When Rahu is in 12 th house with moon or sun and one goes through the Maha Dasha or the Antar Dasha , The soul itself sees illusions that never exists. Fake, smokey figures. Rahu if badly placed even forces and attracts negative energies . Drugs are negative energies. Please don’t believe in all these stuff. Be a little practical. Believe in that one energy , the one positive energy. It’s a spiritual journey guys.