Mental illness affects millions of Americans. Many people with bipolar disorder, depression, and schizophrenia suffer hallucinations, the perception of something that is not present. From phantom smells to hearing voices and seeing things that are not there, hallucinations can take many forms and stem from many causes. It’s not just mental illness, either. Strokes, migraines and inner ear diseases can also lead to hallucinations. And obviously, psychedelic drugs do as well.

Yet surprising