WOW!  This is really interesting!

I'm watching the PBS show, Secrets of the Dead

It hypothesizes that the diseases of people living in the bad old days which prompted the ignorant people to suspect witchcraft/demon possession were caused by ergot fungus on their rye.

Ergot fungus contains a lot of neurotoxins, alkaloids, and hallucinogens that have very dramatic pharmalogical effects on people.  The powerful drug LSD is derived from ergot, as well as medicines to treat migrane headaches (because it constricts blood vessles).

Anyway, the ergot fungus grows on rye grains.  This was a major crop in Salem, MA. It could have contaminated the town's food supply, caused unexplainable hallucinations and physical torment, which was then blamed on witchcraft.

Even more interesting, the witch hunts in Europe occured mostly in rye-producing regions.  Very very interesting.