A group of veterans in Arizona became the first former service members who suffer from post-traumatic stress disorder (PTSD) to be treated with marijuana in a clinical setting. The Scottsdale Research Institute dispensed the marijuana to the 76 veterans on Feb. 6, who volunteered to participate. Some were given the drug itself, while others received placebo doses. The study is part of an effort to determine if and when the use of medical marijuana is safe and effective for treatment of PTSD and other disorders, and whether the Food and Drug Administration should approve its use under medical supervision.