But by using placebo pills for a 7-day span during the month, a regular bleeding period is still experienced.

One problem is how to create the equivalent of placebo pills for a treatment that involves sticking needles into patients.

In addition, the 7 placebo pills contain iron to help replace what is lost during the "pill period."

He assigned 572 others to a placebo pill that looked the same.

Such trials have been chastised for the administration of placebo pills to control groups.

But the new study compared melatonin with placebo pills in a group of subjects.

Dr. Brown cites evidence that patients will respond to placebo pills even after being told this.

Just like real drugs, placebo pills can produce stronger effects in larger doses.

The other part of the group will be given a placebo pill.

This is the control group, who probably got a placebo pill instead of the real pill.