What if a placebo effect explained all the activity of depression treatments?

Many randomized trials have shown that when depressed patients receive no active treatment, e.g. they are administered pill placebo, a large part of them improve anyway. This improvement can be partly explained by natural remission or by the patients’ expectations that a treatment will have an effect on their problems (even when they receive pill placebo). The corollary is that many patients remit even when undergoing exotic therapies, such as...