A randomized controlled trial in Germany found that acupuncture cut tension headache rates almost in half.

Researchers divided 270 patients who reported similarly severe tension headaches into three groups for the study. Over the project's eight-week period, one group received traditional acupuncture, one received only minimal acupuncture (needles inserted at non-acupuncture points, and at only shallow levels), and the third group received neither treatment.

Those receiving the traditional acupuncture reported headache rates of nearly half that of those who received no treatments, suffering 7 fewer days of headaches. The minimal acupuncture group suffered 6.6 fewer days, and the non-acupuncture group suffered 1.5 fewer days. When they received acupuncture after the main study period, the "no treatment" group also reported significantly fewer headache days.

The improvements continued for months after the treatments were concluded, rising slightly as time went on.