Did you question or research the veracity and accuracy of the information you based this article on at all? For instance, the claims of research done at Tulane showing brain damage appears to be a reference to the work of Dr. Heath. If it is, then that research failed peer review miserably.
http://www.nida.nih.gov/WhatsNew/
Go to this NIDA URL and look up Marijuana Research and Dissemination Update - March 2004 [PDF format - 248 Kb] - posted March 12, 2004
You have to download it in PDF format
It has all the current research available you will ever need if you choose to read it.