A van full of U.S. Special Operations veterans crossed the border into Mexico on a sunny day in July to execute a mission that, even to them, sounded pretty far out.

Over a period of 48 hours, they planned to swallow a psychedelic extract from the bark of a West African shrub, fall into a void of dark hallucinations and then have their consciousness shattered by smoking the poison of a desert toad.

The objective was to find what they had so far been unable to locate anywhere else: relief from post-traumatic stress disorder and traumatic brain injury symptoms.

“It does sound a little extreme, but I’ve tried everything else, and it didn’t work,” said a retired Army Green Beret named Jason, who, like others in the van, asked that his full name not be published because of the stigma associated with using psychedelics.

A long combat career exposed to weapons blasts had left him struggling with depression and anger, a frayed memory and addled concentration. He was on the verge of divorce. Recently, he said, he had put a gun to his head.

“I don’t know if this will work,” Jason said of psychedelic therapy. “But at this point, I have nothing to lose.”