Apparently doctors regularly proscribe drugs for their placebo effect. The nytimes has an article detailing the practice.
I myself wholeheartedly believe in the effect. When I was put on a .75 mg dose of Klonopin, it calmed me down immediately. It actually calmed me down even before I got my prescription filled. Later, as I was recounding the medications I was on to a nurse, she said “that’s not doing anything! that’s not enough to be effective.” and i said “Shush! The placebo effect is working just fine.”