https://164.109.178.135/Research-McMichael.asp The environmental factors are still being researched. It's an autoimmune disorder generally, and this one study suspects the Vitamin D a person gets (or doesn't) from exposure to the sun as a deterent.

Stress is a definite factor, also.

I wonder if not only stress, but the increase of medications in our foods as causing the immune system to break down. (As we also have increase in cancers.)

Interesting.