We now know which parts of the brain are involved with feelings of anxiety, sadness and pain.
The two main parts of the brain that increase their activity when we feel stressed or anxious are the prefrontal cortex and the limbic centres. Recent research carried out in USA has shown acupuncture to reduce activity in these areas. The trials were done using fMRI a technique that lets researchers see which parts of the brain are active when the body is stimulated, eg by having an acupuncture needle put into a muscle.
The exciting possibility is that we may be able to treat chronic anxiety and some forms of depression with acupuncture.