The Drug Enforcement Administration (DEA) has given approval for a study that will evaluate the effectiveness of marijuana as a treatment for post-traumatic stress disorder (PTSD), according to The Denver Post.

Researchers plan to enroll 76 veterans at clinics in Phoenix and Baltimore. They will study how well smoking different strains and potencies of marijuana treats PTSD. The marijuana will be supplied by the federal government’s marijuana farm at the University of Mississippi.

Military Times reports it will be the first randomized, controlled research in the United States for PTSD that will use the actual marijuana plant instead of oils or synthesized cannabis.

Some veterans say marijuana eases their PTSD symptoms and has allowed them to stop using prescription medications, but little scientific research supports these claims, the article notes.

“This is a critical step in moving our botanical drug development program forward at the federal level to gather information on the dosing, risks, and benefits of smoked marijuana for PTSD symptoms,” said Amy Emerson, Director of Clinical Research for the Multidisciplinary Association for Psychedelic Studies (MAPS) Public Benefit Corporation. MAPS is the study’s nonprofit sponsor.

MAPS spokesman Brad Burge said once the marijuana has been secured, the group will begin to recruit and enroll participants, perhaps as early as June.

The researchers said results of the study may not be published until 2019.