Placebo Effect
"The Growing Power of the Sugar Pill" by Alix Spiegel
http://www.npr.org/templates/story/story.php?storyId=124367058

A good article on the placebo effect and how the belief in the effectiveness of the treatment can actually convince some people that it is working, even if it is a placebo.

"As part of an experimental study a doctor in Colorado was injecting fetal tissue into the brains of people with Parkinson's. The researchers believed that the experiment was relatively safe, but there was one catch: 40 people would be accepted into the study, but only 20 would get the real operation. Twenty would get a placebo operation; they'd go through everything that the real patients went through without getting the fetal tissue.

So why go through this pain and trouble? Because the doctor knew that even fake surgery — placebo surgery — will often give people relief. And, he felt he needed to compare the effect of the real operation with a fake one. That way he would know what effect the fetal tissue really had"