There is little convincing evidence that acupuncture is effective in reducing pain and serious side-effects continue to be reported, scientists have warned.

UK and Korean researchers carried out a major review of 56 acupuncture studies, which all focused on pain relief. They also looked at case reviews which reported adverse effects.

Acupuncture involves the insertion of fine needles into various parts of the body.

They found that recent results from high-quality studies have shown that various forms of acupuncture, including so-called ‘sham acupuncture', during which no needles actually penetrate the skin, are equally effective for chronic low back pain, and more effective than standard care.

However, in these and other studies, the effects were attributed to such factors as therapist conviction, patient enthusiasm or the acupuncturist's communication style.

But if even sham acupuncture is as good as or better than standard care, then what is the harm? The answer lies in the adverse effect case studies. These studies were grouped into three categories - infection (38 cases), trauma (42 cases) and other adverse effects (13 cases).

Many of these adverse side-effects are not intrinsic to acupuncture, but rather result from the malpractice of acupuncturists. The most frequently reported complications included pneumothorax (penetration of the thorax) and bacterial and viral infections. Five patients died after their treatment.

"Many systematic reviews of acupuncture for pain management are available, yet they only support few indications and contradictions abound," commented lead investigator, Prof Edzard Ernst, of the Universities of Exeter & Plymouth in the UK.

He emphasised that acupuncture remains associated with serious adverse effects.

"One might argue that, in view of the popularity of acupuncture, the number of serious adverse effects is minute. We would counter, however, that even one avoidable adverse event is one too many. The key to making progress would be to train all acupuncturists to a high level of competency," he said.

Details of these findings are published in the journal, Pain. In an accompanying commentary, Dr Harriet Hall, a US doctor who is critical of alternative medicine, pointed out that when a treatment is truly effective, studies tend to produce more convincing results as time passes and the weight of evidence accumulates.

"When a treatment is extensively studied for decades and the evidence continues to be inconsistent, it becomes more and more likely that the treatment is not truly effective. This appears to be the case for acupuncture. In fact, taken as a whole, the published evidence leads to the conclusion that acupuncture is no more effective than placebo," she commented.