The pain-relieving effects of acupuncture with penetrating and non-penetrating needles are largely the same, Japanese researchers say.

In Tuesday's issue of the online journal Open Medicine, researchers described the first double-blind study, the gold standard in clinical research, of acupuncture.

"Needle penetration did not confer a specific analgesic advantage over non-penetrating (placebo) needle application," Nobuari Takakura and Hiroyosi Yajima of Tokyo Ariake University of Medical and Health Sciences concluded in the journal.

In the study, researchers used electrical stimulation to the forearm to provoke pain in 31 healthy men and 25 women with an average age of 32.

Between July 2000 and July 2005, the volunteers were asked to rate the intensity of pain when they received penetrating needles, non-penetrating needles as a control or no acupuncture on a scale of 0 (no pain) to 150. Pain intensity before each needle application was assigned a score of 100.

Pain from penetration

After at least 24 hours to prevent any carry-over or residual analgesic effect, the volunteers received the other type of needle. Neither the acupuncturist nor the subject knew which type of needle was used.

The experiment was designed to study the relationship between pain intensity and de qi — a deep, dull pain associated with needle penetration that is thought to be essential to the analgesic effects of acupuncture.

But that did not seem to be the case.

No significant differences were found between the analgesic effect of penetrating and non-penetrating needles for all seven time points it was measured, up to 40 minutes after removal of the needle.

There was also no significant link between analgesic effect and de qi measured on a scale of 0 to 10, the researchers said.

The needles were designed to be inserted to the same depth and direction for all subjects in the experiment. But in practice, acupuncturists may make adjustments, they noted.

The results support the use of double-blind testing of acupuncture for other types of pain, the researchers said.

Takakura holds patents on the needles used in the study.

Last week, a similar study also found no difference between real and simulated pricks for relieving lower back pain.