Comment Original research (Score 2) 90
Some of the original research in this area was carried out by Angelika Domschke (http://www.linkedin.com/pub/angelika-domschke/19/709/824). For example, this study happened back in 2006 - http://online.liebertpub.com/doi/abs/10.1089/dia.2006.8.89.
Fun fact - Google tried to recruit her and she turned them down after meeting their team.