The US has denied a bid to allow MDMA, commonly known as ecstasy or molly, to be used in the treatment for post-traumatic stress disorder (PTSD).

The US Food and Drug Administration (FDA) was examining the psychedelic drug made by Lykos Therapeutics to treat the mental health disorder in combination with talk therapy.

The drug maker said the agency denied approving the medication over concerns about limited clinical data and whether "psychotherapy contributes to treatment benefit and if it is even necessary". It said the agency requested further study.

The FDA said the lack of data prevented it from "concluding that this drug is safe and effective for the proposed indication".

"The FDA is responsible for ensuring drugs are both safe and effective," the agency told the BBC in a statement on Friday.

"In order to approve a drug, we must determine that the research and data submitted by the sponsor show that the drug is safe and effective for the intended use."

Lykos Therapeutics said it would continue working with the FDA but said additional research could take years to complete. It acknowledged using hallucinogenics to treat PTSD is a "novel" idea but expressed frustration over the setback.

"The FDA request for another study is deeply disappointing, not just for all those who dedicated their lives to this pioneering effort, but principally for the millions of Americans with PTSD, along with their loved ones, who have not seen any new treatment options in over two decades," Amy Emerson, the Chief Executive Officer of Lykos Therapeutics, said in a statement.

This is the first time the agency has considered a psychedelic for medical use.

The drug is currently listed as Schedule I under the Controlled Substances Act, as are cocaine, heroin and cannabis. That classification is defined as drugs "with no currently accepted medical use and a high potential for abuse".

MDMA has been touted as having therapeutic benefits for people suffering from some mental health disorders.

But advisers for the FDA had expressed doubt.

In June, an expert panel at the agency voted 10-1 against the overall benefits of the party drug when used to treat PTSD.

Nine of the 11 advisers said the available data did not show the effectiveness of the drug in patients.

One Lykos Therapeutics trial found 71% from the treatment group no longer met PTSD criteria, compared to 48% from a group taking a placebo.

But FDA panellists voiced numerous concerns with the data.

Issues included that the treatment may not offer long-lasting benefits, concerns about the ways the studies were designed, and the potential risk for heart problems, injury and abuse.

The FDA was not required to follow the committee's vote, but the agency often follows the panel's feedback, which it did in this case.

Last year, Australia's traditionally conservative medicines regulator approved the use of drugs - including MDMA - to assist therapy sessions.