Health is a lot of things. It’s maintaining your body in top functional condition, it’s eating the right foods, it’s doing the right exercise, it’s avoiding sickness, it’s getting the right care if you get sick. But one of the most incredible things about your health is unexplained by the best science (or any other mechanism) available… the Placebo Effect. You’ve probably heard about it, but it’s the ability of your body to repair itself by mimicking the actions of drugs that you didn’t actually take. It’s your own body’s reaction to nothing at all! Unfortunately, it can also give you the symptoms of disease you haven’t been exposed to. It sounds like a fairy tale, but it’s so real that scientists have to guard against its effects in tests of any drug or medical therapy. We all have this hidden ability, but the hard part is “turning it on”… it exists, but it doesn’t work on demand. 
The Dark Side of the Placebo Effect: When Intense Belief Kills
Alexis C. Madrigal in The Atlantic, Sep 14 2011
The Placebo Effect hit these people in their sleep
The Placebo Phenomenon
Cara Feinberg in Harvard Magazine, Jan 2013
An ingenious researcher finds the real ingredients of “fake” medicine.
The Placebo Effect
Skeptic’s Dictionary
Good overview article with excellent background information
How the Placebo Effect Works
Shanna Freeman on How Stuff Works
Placebos aren’t completely explained, but there are some clues
Beware the Nocebo Effect
Enck and Hauser in the New York Times, Aug 10, 2014
Beware- he Placebo Effect can work against you, too
