A 2013 editorial by Steven P. Novella and David Colquhoun found that the inconsistency of results of acupuncture studies (i.e. acupuncture relieved pain in some conditions but had no effect in other very similar conditions) suggests false positive results, which may be caused by factors like biased study designs, poor blinding, and the classification of electrified needles (a type of TENS) as a form of acupuncture. The same editorial suggested that given the inability to find consistent results despite more than 3,000 studies of acupuncture, the treatment seems to be a placebo effect and the existing equivocal positive results are noise one expects to see after a large number of studies are performed on an inert therapy. The editorial concluded that the best controlled studies showed a clear pattern, in which the outcome does not rely upon needle location or even needle insertion, and since "these variables are those that define acupuncture, the only sensible conclusion is that acupuncture does not work." According to the US NIH National Cancer Institute, a review of 17,922 patients reported that real acupuncture relieved muscle and joint pain, caused by aromatase inhibitors, much better than sham acupuncture. Regarding cancer patients, The US NIH National Cancer Institute states that acupuncture may cause physical responses in nerve cells, the pituitary gland, and the brain – releasing proteins, hormones, and chemicals that are proposed to affect blood pressure, body temperature, immune activity, and endorphin release.