Chiropractic is a pseudoscientific complementary and alternative medicine (CAM) that is concerned with the diagnosis and treatment of mechanical disorders of the musculoskeletal system, especially the spine. Chiropractors, especially those in the field's early history, have proposed that such disorders affect general health via the nervous system. The main chiropractic treatment technique involves manual therapy, especially manipulation of the spine, other joints, and soft tissues, but may also include exercises and health and lifestyle counseling. Chiropractors are not physicians or medical doctors.Systematic reviews of controlled clinical studies of treatments used by chiropractors have not found evidence that chiropractic manipulation is effective, with the possible exception of treatment for back pain. A critical evaluation found that collectively, spinal manipulation was ineffective at treating any condition. Spinal manipulation may be cost-effective for sub-acute or chronic low back pain but the results for acute low back pain were insufficient. The efficacy and cost-effectiveness of maintenance chiropractic care are unknown. There is not sufficient data to establish the safety of chiropractic manipulations. It is frequently associated with mild to moderate adverse effects, with serious or fatal complications in rare cases. There is controversy regarding the degree of risk of vertebral artery dissection, which can lead to stroke and death, from cervical manipulation. Several deaths have been associated with this technique and it has been suggested that the relationship is causative, a claim which is disputed by many chiropractors.Chiropractic is well established in the United States, Canada, and Australia. It overlaps with other manual-therapy professions such as osteopathy and physical therapy. Most who seek chiropractic care do so for low back pain. Back and neck pain are considered the specialties of chiropractic, but many chiropractors treat ailments other than musculoskeletal issues. Many chiropractors describe themselves as primary care providers, but the chiropractic clinical training does not support the requirements to be considered primary care providers. Chiropractic has two main groups: "straights", now the minority, emphasize vitalism, "innate intelligence", and consider vertebral subluxations to be the cause of all disease; "mixers", the majority, are more open to mainstream views and conventional medical techniques, such as exercise, massage, and ice therapy.D. D. Palmer founded chiropractic in the 1890s, after saying he received it from "the other world"; Palmer maintained that the tenets of chiropractic were passed along to him by a doctor who had died 50 years previously. His son B. J. Palmer helped to expand chiropractic in the early 20th century. Throughout its history, chiropractic has been controversial. Its foundation is at odds with mainstream medicine, and has been sustained by pseudoscientific ideas such as vertebral subluxation and innate intelligence. Despite the overwhelming evidence that vaccination is an effective public health intervention, among chiropractors there are significant disagreements over the subject, which has led to negative impacts on both public vaccination and mainstream acceptance of chiropractic. The American Medical Association called chiropractic an "unscientific cult" in 1966 and boycotted it until losing an antitrust case in 1987. Chiropractic has had a strong political base and sustained demand for services; in recent decades, it has gained more legitimacy and greater acceptance among conventional physicians and health plans in the United States.