Acupuncture - real or sham - is more effective at treating back pain than conventional therapies, research suggests.
Acupuncture is said to release the body's vital energy
A German team found almost half the patients treated with acupuncture felt pain relief.
But the Archives of Internal Medicine study also suggests sham acupuncture works nearly as well as the real thing.
In contrast, only about a quarter who received drugs and other Western therapies felt better.
The researchers, from the Ruhr University Bochum, say their findings suggest that the body may react positively to any thin needle prick - or that acupuncture may simply trigger a placebo effect.
One theory is that pain messages to the brain can be blocked by competing stimuli.
Researcher Dr Heinz Endres said: "Acupuncture represents a highly promising and effective treatment option for chronic back pain.
"Patients experienced not only reduced pain intensity, but also reported improvements in the disability that often results from back pain and therefore in their quality of life."
Needles not manipulated
More than 1,100 patients took part in the study. They were given either conventional therapy, acupuncture or a sham version.
Although needles were used in the sham therapy, they were not inserted as deeply as in standard acupuncture. Neither were they inserted at points thought key to producing a therapeutic effect, or manipulated and rotated once in position.
After six months 47% of patients in the acupuncture group reported a significant improvement in pain symptoms, compared to 44% in the sham group, and just 27% in the group who received conventional therapy.
Dr James Young, of Chicago's Rush University, said: "We don't understand the mechanisms of these so-called alternative treatments, but that doesn't mean they don't work."
Acupuncture is based on the ancient Chinese theory that needles can be used to release the body's vital energy, or qi.
Conventional therapies tested in the study included painkillers, injections, heat therapy and massage.
It is estimated that as many as 85% of the population experiences back pain at some point, and the problem costs the NHS around £500m a year.
The study echoes the findings of two studies published last year in the British Medical Journal, which found a short course of acupuncture could benefit patients with low back pain.
Mike O'Farrell, of the British Acupuncture Council, said: "Through these controlled research findings demonstrating the effectiveness of acupuncture, we believe that both the medical health profession and members of the public will see the benefits of acupuncture as part of an integrated healthcare service."
However, Paul Ingraham, a registered massage therapist, said the study did not provide evidence that acupuncture was an effective therapy for back pain.
"On the contrary, it strongly shows that the central claims of acupuncturists are empty, and that all the 'skill' and 'craft' of acupuncturists is no better than random needling.
"Patient optimism is a key factor in back pain rehabilitation, and any therapy that people feel good about is likely to outperform conventional therapy."