It looks like nobody knows for sure.. initial viral infection in my case, then almost a year later stress at school, probably genes helped too...
The poll is a bit.. Limited. There are other forms of infections, not to mention chemical exposure (industrial exposure, pesticides in ones home etc). There is also slow-onset without definite cause etc.
That didn't stop me from voting though.
If I (or anyone) knew the answer to that definitively, then we would be on the way to fixing it.
Mine felt like a virus.
One person getting A after having B done is not a proof of cause.