Do antidepressants work? The difference between the effect of a placebo and the effect of an antidepressant is minimal for most people," says Harvard scientist Irving Kirsch. Kirsch's views are of vital interest to the 17 million Americans who take the drugs, including children as young as six and to the pharmaceutical industry that brings in $11.3 billion a year selling them. Irving Kirsch is the associate director of the Placebo Studies Program at Harvard Medical School. He says that his research challenges the very effectiveness of antidepressants. Kirsch's specialty has been the study of the placebo effect: the taking of a dummy pill without any medication in it that creates an expectation of healing that is so powerful, symptoms are actually alleviated. Kirsch, who's been studying placebos for 36 years, says "sugar pills" can work miracles. Kirsch: Placebos are great for treating a number of disorders: irritable bowel syndrome, repetitive strain injuries, ulcers, Parkinson's disease. Even traumatic knee pain. In this clinical trial some patients with osteoarthritis underwent knee surgery, while others had their knees merely opened and then sewn right back up. In terms of walking and climbing, the people who got the placebo actually did better than the people who got the real surgery. And that lasted for a year. At two years after surgery, there was no difference at all between the real surgery and the sham surgery. It's not all in your head because the placebos can also affect your body.