Just as cannabis is gaining traction as a legitimate treatment option for military veterans, the U.S. Food and Drug Administration has given the "breakthrough therapy" designation to MDMA — the main chemical in the club drug Ecstasy — for treatment of post-traumatic stress disorder, or PTSD.

The move appears to pave the way for a Santa Cruz, Calif.-based advocacy group to conduct two trials of MDMA-assisted psychotherapy for patients with severe PTSD.

The nonprofit group Multi­disciplinary Association for Psychedelic Studies plans to test out the strategy on 200 to 300 participants in clinical trials this spring.

"For the first time ever, psychedelic-assisted psychotherapy will be evaluated in [advanced] trials for possible prescription use, with MDMA-assisted psychotherapy for PTSD leading the way," said Rick Doblin, the group's executive director.

The FDA doesn't disclose the names of drugs that receive "breakthrough therapy" designation. But if a researcher or drug company chooses to release that information, they are allowed to. In this case, the Psychedelic Studies group is the researcher.

Veterans have pushed for new treatments for PTSD, which some consider the "signature" injury of the wars in Iraq and Afghanistan. Symptoms include depression, isolation, inability to concentrate and, in the extreme, suicidal thoughts.

Groups as big as the American Legion have called for the federal government to loosen restrictions on cannabis research for PTSD, traumatic brain injury and other combat-related wounds.

The Veterans Affairs secretary recently opened the door to pot, saying in June that there "may be some evidence this is beginning to be helpful and we are interested in looking at that."

A "breakthrough therapy" is a classification granted by the FDA when preliminary clinical evidence shows "substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development."

MDMA has been tested in past clinical trials on patients with anxiety.

The drug gained prominence in dance clubs, with the common nicknames Ecstasy and Molly.

At present, the U.S. Drug Enforcement Administration lists it as a Schedule I drug, which means there are no currently accepted medical uses and there's a high potential for abuse.

The drug affects serotonin use in the brain.

It can cause euphoria, increased sensitivity to touch, sensual and sexual arousal, the need to be touched and the need for stimulation.

Some unwanted psychological effects can include confusion, anxiety, depression, paranoia, sleep problems and drug craving, according to the DEA.

Clinical studies suggest that MDMA may increase the risk of long-term problems with memory and learning.