Vertebrobasilar artery stroke (VAS) is statistically associated with chiropractic services in persons under 45 years of age, but it is similarly associated with general practitioner services, suggesting that these associations are likely explained by preexisting conditions. Weak to moderately strong evidence supports causation (as opposed to statistical association) between cervical manipulative therapy (CMT) and VAS. There is insufficient evidence to support a strong association or no association between cervical manipulation and stroke. While the biomechanical evidence is not sufficient to support the statement that CMT causes cervical artery dissection (CD), clinical reports suggest that mechanical forces have a part in a substantial number of CDs and the majority of population controlled studies found an association between CMT and VAS in young people. It is strongly recommended that practitioners consider the plausibility of CD as a symptom, and people can be informed of the association between CD and CMT before administrating manipulation of the cervical spine. There is controversy regarding the degree of risk of stroke from cervical manipulation. Many chiropractors state that, the association between chiropractic therapy and vertebral arterial dissection is not proven. However, it has been suggested that the causality between chiropractic cervical manipulation beyond the normal range of motion and vascular accidents is probable or definite. There is very low evidence supporting a small association between internal carotid artery dissection and chiropractic neck manipulation. The incidence of internal carotid artery dissection following cervical spine manipulation is unknown. The literature infrequently reports helpful data to better understand the association between cervical manipulative therapy, cervical artery dissection and stroke. The limited evidence is inconclusive that chiropractic spinal manipulation therapy is not a cause of intracranial hypotension. Cervical intradural disc herniation is very rare following spinal manipulation therapy.
D. D. Palmer founded chiropractic in the 1890s, after saying he received it from "the other world", and his son B. J. Palmer helped to expand it in the early 20th century. Throughout its history, chiropractic has been controversial. 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.
A 2006 systematic cost-effectiveness review found that the reported cost-effectiveness of spinal manipulation in the United Kingdom compared favorably with other treatments for back pain, but that reports were based on data from clinical trials without sham controls and that the specific cost-effectiveness of the treatment (as opposed to non-specific effects) remains uncertain. A 2005 American systematic review of economic evaluations of conservative treatments for low back pain found that significant quality problems in available studies meant that definite conclusions could not be drawn about the most cost-effective intervention. The cost-effectiveness of maintenance chiropractic care is unknown.
Studies have not confirmed the effectiveness of prolotherapy or sclerotherapy for pain relief, used by some chiropractors, osteopaths, and medical doctors, to treat chronic back pain, the type of pain that may come on suddenly or gradually and lasts more than three months. The therapy involves injections such as sugar water or anesthetic in hopes of strengthening the ligaments in the back.