Seventy-five people were tested after specific chiropractic cervical adjustments. Both systolic and diastolic blood pressure decreased significantly in the adjusted group. No significant changes occurred in the control group. In those with the highest pre-treatment blood pressures, the treatment effect was greatest, indicating that the effective in hypertensives may be even more significant.
McKnight ME, DeBoer KF J Manipulative Physiol Ther. 1988 (Aug);11 (4): 261-266