Here's an example of how much credibility you can put into studies that start out with the intention of proving something.

http://throwawayyourtv.com/2006/05/s...-bullshit.html
Hamlet Reviewed by Hamlet on . Up in Smoke: Marijuana Toasts Memory By Robert Roy Britt LiveScience Managing Editor posted: 13 March 2006 04:01 pm ET If you can't remember the headline of this article or are already struggling to recall some of the words at the beginning of the story, try hard to recall how much pot you smoked in your youth. A new study finds those who've used a lot of marijuana have worse memories and don't think as quickly. Rating: 5