What caused the Salem Witch Trial hysteria in 1692?

In the late 1600s, Massachusetts was heavily Puritan.  Puritan beliefs demanded moral behavior and a devotion to Christianity and the church.  Those who were different were viewed with suspicion.  This was especially true of people who held different religious beliefs, such as Quakers and Native Americans.
In 1692, two girls living in Salem Village started to experience strange fits.  They were cousins Betty Parris and Abigail Williams.  Betty was the minister's daughter and Abigail was his niece.  It was recorded that they made animal sounds, threw themselves onto the floor, and tossed objects around the house.  This behavior was highly unusual for Puritan young ladies, who were expected to be meek and respectable.  It was especially unusual for members of the minister's own family to behave in such a way.  Soon other girls in Salem Village started to experience similar fits.  It was concluded that all the girls had been bewitched.  This was given as the explanation for their strange behavior.  These girls soon started making accusations about local villagers in Salem.  They accused them of being involved with witchcraft.
The girls began acting strangely in the wintertime.  It had been a long, cold winter in Salem Village.  An earlier outbreak of smallpox had left villagers fearful.  In addition, battles were raging less than 100 miles away due to the Indian Wars.  It was a time of fear and hardship, which most likely left villagers more suspicious than normal.  They may have wanted something to blame for their hardships.
More and more people in the area were accused of bewitching the girls.  Some of the accused even made confessions.  Some of the people who were accused were fairly prominent in the local church.  Neighbors became suspicious of each other.  Tensions rose in and around Salem Village.  Eventually, the hysteria died down.  This did not, however, stop several people from being falsely hung for witchcraft.
One modern theory suggests that the girls who experienced the strange fits had eaten grain with a fungus known as ergot.  The drug LSD is derived from ergot.  One who eats grain that has been compromised by the fungus can become physically ill, and even experience hallucinations.  This would explain the strange behaviors of the girls involved.
 
http://law2.umkc.edu/faculty/projects/ftrials/salem/SAL_ACCT.HTM

http://people.ucls.uchicago.edu/~snekros/Salem%20Journal/Hysteria/ElbertDLukeR.html

http://www.pbs.org/wnet/secrets/witches-curse-clues-evidence/1501/