I read a medical-thriller based upon that same belief a few years ago. I am unsure of the title, but the author is Robin Cook (who is well known for his realistic medical-thrillers). The book didn't say that it was LSD specifically, but some other hallucenogenic (sp?) drug that was extracted from the grains. In the novel, a young woman inherits a house in Salem and discovers that her ancestors were branded as witches. Soon, her world is turned upside down as "witches" begin to appear again. It was a very enthralling read, and I recommend it to anyone interested in the Salem Witch Trials and this belief that they may have been influenced by natural forces, rather than religious ones. If I can remember the title, I'll post it here. I should have the book in my library somewhere.

AJ