Participants with chronic or recurrent headache, unrelated to any known pathology or disease, will be randomly assigned to one of four interventions: Osteopathic manipulation of the body other than the head, osteopathic manipulation of the head, osteopathic manipulation of the head and rest of the body, or light touch on the head only but no manipulation. Measurements of heart rate and blood pressure variability, peripheral blood flow, and behavioral changes, such as mood, pain duration, intensity and frequency will be assessed.