From various studies, here is a summary of several http://www.druglibrary.org/schaffer/lsd/adverse.htm search around and you can find pdf's of various studies, the citations of the provided link should point you in the right direction hm most of that link actually talks about common knowledge stuff, I will have to dig around for some research papers, they go into much more detail and discuss the methods they use for testing and the results a lot more. Here is one excerpt from the provided link