It enhances the feelings you are experiencing already. If those are negative to begin with, I'd worry about people having a bad trip and hurting themselves (even inadvertently like stumbling into traffic).

If you already have a mental condition such as schizophrenia it may cause a bad reaction. Mushrooms give an experience of disconnecting from reality or existing outside of your own body. Not the greatest move for someone already having problems with reality.

Psychiatric condition may end up much worse than before