“Not everything that counts can be counted; not everything that can be counted counts”. Albert Einstein.
There is a considerable body of research evidence about the effectiveness of acupuncture. However, because the approach is different for each individual, and because the approach will be modified as your health comes more into balance, it does not fit very well into the research model that is used for drug trials, that scientists regard as the best (the randomised controlled trial, or RCT).
Research findings need to be carefully evaluated. If you would like to look into the research evidence about acupuncture you can find a selection at the the Acupuncture Research Resource Centre or the British Acupuncture Council.
A list of conditions for which acupuncture may be helpful is listed at The World Health Organisation. In the UK, acupuncture is used within the NHS for pain relief, and acupuncture is part of the healthcare system in Switzerland, China and many Asian countries.