The decision is the latest sign that federal health officials want more research on medical marijuana as its use grows.

The move marks a rare action by the FDA to sanction a study on cannabis despite the plant’s current Schedule I classification under federal law as a drug with no therapeutic use, in the same category as heroin and LSD.

The Food and Drug Administration (FDA) this week authorized a long-delayed clinical trial to test whether smoking marijuana can be used to treat post-traumatic stress disorder (PTSD) in

FDA approves Phase 2 cannabis trial for veterans with PTSD, funded by Michigan marijuana taxes. Study to assess smoked cannabis efficacy.

After a three-year negotiation, the FDA has dropped its objection to allowing patients to self-titrate dosing of smoked cannabis. But regulators want to see additional information about the device that will be used for inhalation.

More than 300 veterans diagnosed with post-traumatic stress disorder will take part in a five-week study approved by the Food and Drug Administration to examine the effects of smoking cannabis on symptoms from the illness.

The FDA rejected the approval request for cannabis-based clinical trials five times with “partial clinical hold letters,” but MAPS kept hammering and finally won after it said internal changes were made at the agency’s Division of Psychiatry and in its work on cannabis, the organization said.