THURSDAY, Oct. 23 (HealthDay News) -- American doctors regularly prescribe placebo pills that are intended to have a psychological effect, a new survey finds.

However, the placebos reported by the 679 physicians in the survey often aren't the inactive substances used in controlled clinical trials, said Dr. Farr A. Curlin, an assistant professor of medicine at the University of Chicago, and a member of the team reporting the finding in the Oct. 24 issue of the BMJ.

"Most people when they say 'placebo' think of something like a sugar pill," Curlin said. "But doctors can use a treatment that may have some effects but that they think will not have a direct effect on the patient except by the placebo effect."

The placebo effect, well-established in countless studies, is a benefit produced by assuring someone that whatever is being given will benefit whatever the problem happens to be -- "optimism or confidence that something is being done," as Curlin phrased it.

Only 3 percent of the doctors responding in the survey reported prescribing sugar pills. But 41 percent said they used over-the-counter painkillers as placebos, 38 percent used vitamins, 13 percent used antibiotics, and 13 percent used sedatives.

The survey also found that only 5 percent of the doctors who prescribe a placebo treatment describe it as such. The great majority, 68 percent, describe it as a potentially beneficial medicine or treatment not typically used for the condition.

And almost two-thirds of the doctors in the survey said they believed the practice to be ethically permissible.

"It's a gray zone," Curlin said. "It is not ethical to actively deceive patients. But when doctors give something which they think will help but don't think it helpful to explain the full reasoning about why it will help, that's a gray zone."

Placebo treatment "is pretty common in the practice of medicine," said Curlin, who acknowledged using it. "I give people the information I think a reasonable person would want to know, trying to be as candid as possible," he said. "There are times when I have said, 'Yes, I think it might be helpful, why don't you give it a try,' when I don't have confidence it will help their condition."