A panel of advisers to the U.S. health regulator today voted against a therapy based on the party drug MDMA for patients with post-traumatic stress disorder, in a major setback to the nascent field of psychedelic treatments.

The panel voted 10-to-1 against the therapy, saying the benefits did not outweigh its risks, while nine of the 11 members said the available data did not show the effectiveness of the drug in PTSD patients.

MDMA, commonly known as ecstasy or molly, has been long seen as a potential therapy for mental health disorders, despite being known for its illicit use.

The treatment, a capsule form of MDMA made by public-benefit corporation Lykos Therapeutics, was meant to be administered in combination with talk therapy sessions by a licensed mental health provider.

Over 190 patients, who received doses of MDMA in addition to therapy, showed a significant reduction in PTSD scores compared to placebo.

The FDA’s staff reviewers on Friday raised concerns that patients in the trials were aware of whether they were given MDMA or a placebo due to its psychedelic effects, preventing an objective view of how well the drug worked.

The FDA, during the panel meeting, said there was a “striking lack” of documentation of abuse-related adverse events, which may limit the agency’s ability to explain the effects of MDMA or determine its abuse liability.

Scrutiny into Lykos’ drug has increased in recent months after an influential nonprofit, the Institute for Clinical and Economic Review (ICER), said there was “insufficient” evidence for the benefits of MDMA-based therapy.

In a letter dated Monday, the American Psychological Association echoed those comments, saying its panel of experts could not determine the balance of benefits and potential harms.

PTSD affects 13 million Americans and is especially common among war veterans. There is a large unmet need for new treatments for the disorder as existing drugs do not work on all patients.

The FDA’s staff on Friday proposed restrictions around Lykos’ drug and a need to monitor its usage in briefing documents. The staff also flagged a rise in blood pressure and pulse in the trials, and in cases of liver toxicity.