Post-traumatic stress disorder closes people off. They withdraw — often reluctant to talk about what they’ve experienced and unable to trust others or themselves. But many leading treatments for the condition require just that.

The treatments for PTSD — including several forms of psychotherapy and medication — are effective for many patients, but they don’t work for everyone. They can be expensive. Sometimes, they can be so distressing that patients stop the treatment before it’s complete.

“The field has acknowledged for years that we need to do better for our patients,” Dr. Jerry Rosenbaum, a professor of psychiatry at Harvard Medical School, said Tuesday at a meeting of experts tasked with advising the Food and Drug Administration on whether to approve the first new medication in decades for PTSD. The treatment combines the psychoactive drug MDMA with talk therapy to treat PTSD.

The expert panel voted against endorsing the therapy, which was developed by Lykos Therapeutics, citing concerns about safety and issues in clinical trials. The F.D.A. is not required to follow the guidance of these advisory panels, but often does.

But even in rejecting the use of MDMA-assisted therapy, the experts emphasized the need for new and better treatments for PTSD, which can cause intrusive thoughts, flashbacks and nightmares and increases the risk of suicide or death from other causes.

Roughly six percent of the American population will develop PTSD at some point in their lives. Only a fraction of those patients currently recover, Dr. Tiffany R. Farchione, director of the F.D.A.’s Division of Psychiatry Products, said at the meeting Tuesday. And many people with PTSD symptoms struggle to get diagnosed in the first place.