Why do somepeople suffer from sleep paralysis?

Question: Why do somepeople suffer from sleep paralysis?
- Keywords:
  conditions,
  illness,
  paralysis,
  sleep,
  suffer
Asked by hazellwh to Helen, Jenni, Mark, Martin, Stu on 16 Jun 2011.
- Helen O'Connor answered on 16 Jun 2011:
  
  Wow – this is a big question to answer and I am afraid I couldnt help here, apart from to say that it is quite common, and a reasonable number of people experience sleep paralysis at some time or other in their life.
  
  There are some good explanations here that are quite scientific http://www.bbc.co.uk/dna/h2g2/A6092471

Question: Why do somepeople suffer from sleep paralysis?