PHILADELPHIA — Acupuncture proved no more effective than sham treatments for treating pain from a common chronic condition, according to a new study.

For 12 weeks, researchers tested conventional acupuncture against treatments in which needles were improperly applied in 100 Seattle-area patients suffering from fibromyalgia, which is characterized by chronic pain in the head and torso.

The study concluded that adding acupuncture to other treatments the patients were already using provided no greater pain relief than sham acupuncture treatments, according to yesterday's issue of Annals of Internal Medicine.

"We did not find that acupuncture reduced pain in patients with fibromyalgia," the study concluded.

Researcher Dr. Dedra Buchwald of the University of Washington said the results were a surprise, given stories and testimonials from fibromyalgia patients who say acupuncture helps.

"We've seen it ourselves in our patients, that they swear by it; they have a lot of faith that acupuncture works," she said.

In the study, patients in all the groups improved, but very early, after only one or two treatments — far earlier than most acupuncturists would expect an improvement — and then remained at the same level for the rest of the study, Buchwald said.

The results could mean that any form of acupuncture results in some form of improvement, or that simply enrolling in the study and being hopeful about the outcome spurred an initial improvement in patients, she said.

The sham treatments — acupuncture for an unrelated condition, needle insertion at points that are not used in acupuncture and simulated acupuncture that didn't actually pierce the skin — were intended to help pinpoint what elements of acupuncture might be beneficial.

Buchwald cautioned that acupuncturists generally tailor treatment for each patient and often combine it with other forms of treatment, which cannot be done in a clinical trial.

Acupuncture, she said, "certainly works in acute pain control and it works in some conditions of chronic pain, so I don't think this is to say that acupuncture doesn't work at all."

Fibromyalgia is the second most common rheumatologic condition after osteoarthritis, and affects 2 to 4 percent of the U.S. population. Patients suffer chronic and widespread pain and sensitivity to pressure at various points on the body.

The cause of the condition is unknown, there are no laboratory tests for it and no treatments have proved effective, the researchers said.