"The Placebo Effect."

"In most cases, the larger the pill, the stronger the placebo effect. Two pills are better than one, and the brand-name pills trump generics. Capsules are generally more effective than pills, and injections produce a more pronounced effect than either. There is even evidence to suggest that the color of medicine influences the way one responds to it: colored pills are more likely to relieve pain than white pills; blue pills help people sleep better than red pills; and green capsules are the best bet when it comes to anxiety medication."

Excerpt from The Power of Nothing by Michael Specter.