“Cervical spine manipulation was associated with significant improvement in headache outcomes in trials involving patients with neck pain and/or neck dysfunction and headache.” — Duke Evidence Report, McCrory, Penzlen, Hasselblad, Gray (2001) “The results of this study show that spinal manipulative therapy is an effective treatment for tension headaches. . . Four weeks after cessation of treatment . . . the patients who received spinal manipulative therapy experienced a sustained therapeutic benefit in all major outcomes in contrast to the patients that received amitriptyline therapy, who reverted to baseline values.” ‘ — Journal of Manipulative and Physiological Therapeutics, Boline et al. (1995)