The FDA-approved study is the first of its kind because it allows researchers to actually give veterans pot to smoke. Up until now, studies on medical marijuana and post-traumatic stress disorder have all been observational. That means researchers were aware of the fact that the study participants were smoking up or otherwise using weed. But they couldn’t hand out joints or edibles themselves.

One study looked at patients who signed up for New Mexico’s Medical Cannabis Program. New Mexico was the first state to include PTSD as a condition eligible for medical marijuana. The study aimed to analyze the effectiveness of medical marijuana for post-traumatic stress disorder symptoms.

It involved administering the Clinician-Administered Posttraumatic Scale for DSM-IV, or CAPS, to gauge patients’ symptoms. When patients were using cannabis, the majority had a more than 75 percent reduction in symptoms compared to when they were not using cannabis.