Research into the Salem Witch trials should include a study of Ergot. A fungi growth on cereal plants including rye. A lysergic fungi,it can have profound LSD like symptons. Cause delusions,miscarriges,hallucinations and death. It can also cause extreme contortions. So in effect a food poisoning,Ergot,that comes and goes with cycles controlled by unusual rainy seasons,could well be the root cause of the symptons.
I believe the history channel covered a study of Ergot and Witchcraft outbreaks in the Middle Ages.
Hope this helps,it should be a good study.