Chiropractic education trains future people in chiropractic, a form of alternative medicine concerned with the diagnosis and treatment of mechanical disorders of the musculoskeletal system, especially the spine, under the belief that such a disorder affects general health via the nervous system. Numerous controlled clinical studies of treatments used by chiropractors have been conducted, with conflicting results. Systematic reviews of this research have not found evidence that chiropractic manipulation is effective, with the possible exception of treatment for back pain. Throughout its history chiropractic has been the subject of internal and external controversy and criticism.