“The big news is that it’s not a couple of thousand people who are affected — it’s a couple million people,” said Dr. Joseph Habboushe, an assistant professor of emergency medicine at N.Y.U. Langone/Bellevue Medical Center and lead author of the new paper, published in Basic & Clinical Pharmacology & Toxicology.

Others questioned the one-in-three figure, however. Paul Armentano, the deputy director for the National Organization for the Reform of Marijuana Laws (NORML), said that even with more widespread use of marijuana, “this phenomenon is comparatively rare and seldom is reported” and strikes only “a small percentage of people.”

And several physicians who routinely prescribe medicinal marijuana for conditions ranging from chronic pain to epilepsy said they have not seen the cyclic vomiting syndrome in their patients, but noted that they typically prescribe compounds that are not designed to produce a high and contain very low amounts of the psychoactive ingredient THC.

Dr. Habboushe said doctors in other parts of the country may be unfamiliar with C.H.S. or mistake it for a psychiatric or anxiety related syndrome. And even if they are aware of it, many regard it as a “rare, kind of funny disease,” replete with anecdotes of patients who spend hours in the shower.

But the condition can be quite serious. One 33-year-old military veteran who asked not to be identified by name described bouts lasting up to 12 hours in which he felt “like a puffer fish with sharp spikes was inflating and driving spikes into my spine from both sides. I’ve broken bones, and this blew it out of the water.”

“I know patients who have lost their jobs, gone bankrupt from repeatedly seeking medical care, and have been misdiagnosed for years,” Dr. Habboushe said.

“Marijuana is probably safer than a lot of other things out there, but the discussion about it has been so politicized and the focus has been on the potential benefits, without looking rigorously at what the potential downside might be,” he said. “No medication is free from side effects.”