Antidepressants matter a lot for several reasons. The illness destroys people's lives. It affects large numbers of people—about one person in five has an episode of major depression at some point in their lives. Depression also increases with economic development and affluence and is virtually unknown in subsistence societies.
Much has been written about the benefits of modern anti-depressants of which prozac is a (talkative) poster child. A 2002 study analyzed FDA data on the 6 most widely prescribed antidepressants (1). It found that placebos had about 80% as much effect as the drugs themselves, suggesting that "the pharmacological effects of antidepressants are clinically negligible." A large dose had no more effect than a smaller one.
The hits keep coming. A widely read 2010 JAMA article (2) went so far as to say that most people taking anti-depressant drugs do no better than if they had received a sugar pill. This paper was widely misinterpreted by journalists as saying that anti-depressants were of no practical value. In reality, the paper showed that the drugs are effective for individuals who are severely depressed (although why they work remains a mystery). Most of the people receiving antidepressants are not severely depressed, though.
Limited clinical effectiveness is not the whole story either. Depression is a persistent illness and any medicine that is taken for a long period may produce troublesome side effects, although side effects of widely prescribed drugs are mostly mild and brief.
Taking anti-psychotic drugs over long periods is expensive and it may prevent people from dealing with problems in more constructive ways. To take the simplest kinds of intervention, people who are physically fit and get regular exercise are less likely to become depressed. Likewise, those who have a good social support system are less likely to succumb to psychological stressors.
It is clear that antidepressants are vastly over-prescribed and that the many behavioral and psychological interventions for depression are under used and under researched. The placebo effect is one psychological intervention strongly supported by evidence.
The usefulness of placebos for depression has fascinating implications If placebos are used in medical treatment, there are a myriad of ethical issues relating to how, and whether they should be preferred to active drug interventions with their toxicity and side effects.
Apart from the risk of denying drug treatment to individuals who are more severely depressed than they seem, there is the nagging issue as to how placebos can be administered without committing fraud.
Then there is the problem of mixing scientific medicine with mysticism and shamanism. Judging from anthropological evidence, placebos can be as powerfully administered by faith healers and medicine men as by practitioners of scientific medicine.
The point is, if physicians are licensed to prescribe largely magical remedies, why are shamans not licensed to practice medicine?
2. Fournier, J. C., et al. (2010). Antidepressant drug effects and depression severity. JAMA, 303, 47-53.