In a study funded by NIH’s National Center for Complementary and Alternative Medicine to test the effectiveness of different approaches for treating mechanical neck pain, 272 participants were divided into three groups that received either spinal manipulative therapy (SMT) from a doctor of chiropractic (DC), pain medication (over-the-counter pain relievers, narcotics and muscle relaxants) or exercise recommendations. After 12 weeks, about 57 percent of those who met with DCs and 48 percent who exercised reported at least a 75 percent reduction in pain, compared to 33 percent of the people in the medication group. After one year, approximately 53 percent of the drug-free groups continued to report at least a 75 percent reduction in pain; compared to just 38 percent pain reduction among those who took medication.
-- Bronfort et al. (2012), Annals of Internal Medicine