Acupuncture has been claimed to be associated with activation of the endogenous antinociceptive system. The analgesic effects of acupuncture have been ascribed to β-endorphin interacting with opioid receptors. However, firstly, the release of β-endorphin into the blood has been proven to be induced by stress, i.e. under dysphoric conditions, and, secondly, if released under stress, β-endorphin has been shown not to be analgesic. Our aim was to test whether β-endorphin immunoreactive material is released into the cardiovascular compartment during acupuncture comparing the most frequently used types of acupuncture with standard pain treatment under apparently low stress conditions.

This prospective study included 15 male patients suffering from chronic low back pain. β-Endorphin immunoreactive material and cortisol were measured in the plasma of patients who underwent, in randomorder, therapy according to a standard pain treatment, traditional Chinese acupuncture, sham acupuncture, electro acupuncture and electro acupuncture at non-acupuncture points before, at and after the treatment. Statistical analysis was performed using two-way ANOVA with repeated measures.

A decrease in plasma cortisol concentration measured over the five treatment protocols was highly significant (P < 0.001). The β-endorphin immunoreactive material concentrations in plasma were minimal at all times and in all treatment conditions. The influence of treatments by various acupuncture procedures on cortisol and β-endorphin immunoreactive material plasma concentrations over the three time points was not significantly different.

β-endorphin immunoreactive material in blood is not released by any type of acupuncture as tested under low stress conditions.