Acupuncture -- and even simulated acupuncture using toothpicks --appears to relieve symptoms of chronic low back pain better than the standard treatment, a large study has found.

The study found that 60 per cent of participants who received any one of three types of acupuncture - customized, standard and simulated acupuncture - reported they had improved function after eight weeks of treatment.

That compares to just 39 per cent of those who received standard care of their choice, which could include a doctor's visit, chiropractic treatment or massage.

The fact that the simulated acupuncture had the same effect as the real acupuncture raises questions about how acupuncture works to relieve pain, the authors note.

For the study, researchers recruited 683 adults aged 18 to 70 with chronic lower back pain, none of whom had ever before had acupuncture and who had rated the "bothersomeness" of their pain as at least a 3 on a 0-to-10 scale.

One group had needles inserted under the skin in a pattern tailored to their particular back pain by a diagnostic acupuncturist. The second group got the standardized arrangement of needles for back pain.

A third group received simulated acupuncture, in which toothpicks were pressed against acupuncture points without going through the skin.

After eight 26, and 52 weeks, researchers measured back-related function and how much symptoms bothered participants.

The researchers found that at eight weeks, all three acupuncture groups reported improved dysfunction scores significantly more than the group receiving usual care. Members of all three groups were able to reduce their medication use to control their low back pain.

There was no significant difference between the groups receiving the needle and simulated forms of acupuncture. Thus, neither tailoring acupuncture needle sites to an individual patient nor penetrating the skin appears to be important for relieving pain.

A follow-up one year later showed 59 per cent to 65 per cent of those in the acupuncture groups were still experiencing improvement, compared with 50 per cent of those in the usual-care group.

The findings are reported in this week's issue of the Archives of Internal Medicine.

"The findings of this research show that acupuncture-like treatments, including simulated acupuncture, can elicit positive responses," said Dr. Josephine P. Briggs, director of the National Center for Complementary and Alternative Medicine (NCCAM), which funded the study.

"This adds to the growing body of evidence that there is something meaningful taking place during acupuncture treatments outside of actual needling.

The authors note that more research is needed to understand what is evoking these responses.

The authors theorize there could be a few factors at play affecting response: the patients may have expectations of pain relief; the setting that they received the treatment and the reassurances of the practitioner may have also helped. Or there may have been some effects of non-insertive stimulation of acupuncture points.