In a 28-week study of Alzheimer's patients, 250 were in a randomized trial to memantine or placebo.

CNN: Better understanding of dementia leading to more effective therapies

To really know whether antidepressants have long-term health risks, one would have to do a very, very large study in which 50 percent of the subjects were randomized to receive an antidepressant and the other 50 percent were randomized to take a placebo pill.

CNN: What are antidepressants' long-term effects?

The latest study, a randomized trial of 80 women and men published in Plos One by Harvard researchers, shows that even when clinicians told women with irritable bowel syndrome they are getting fake pills, the fake pills still worked.

FORBES: Sugar Pills Work Even When People Know They Are Fake