There is. And because of it doctors really want to use marijuana derivatives. I know some of the folk running the NHS studies and doing some of the PHD work on endocrine effects.
Here's a couple of recent studies on Sativex.
http://www.gwpharm.com/oncology.aspx
http://www.gwpharm.com/GW%20Pharmaceuticals%20Announces%20Ne...
Also, you have organisations like Law Enforcement Against Prohibition, who have been working heavily behind the scenes for the past decade. http://www.leap.cc/