There isn't any because it's a schedule 1 drug and to be able to do research on how it works or can help (if it can) can't even be studied. Rand Paul, Cory Booker, and Kirsten Gillibrand have a bill introduced March 10, 2015 to change it to schedule 2 and some other thing SO it can be studied but it's stuck in committee for $ome unknown reason.
http://www.drugpolicy.org/news/2015/03/senators-cory-booker-d-nj-rand-paul-r-ky-and-kirsten-gillibrand-d-ny-introduce-historic
It would also allow the VA to prescribe it to veterans as it does help some with PTSD.
I know all this because I watched a program on Vice, a new channel I found on DirectTV. On the show Weediquette they had an episode called "Stoned Vets". It also chronicles a doctor who wants to study it and all the hoops she has to go through to be able to test it. Still hasnt been able to yet. Watch it if you get the chance.