The placebo effect is based on the expectation of treatment, and its effects are insidious.  Depression has long been known to be a disease which is strongly susceptible to the placebo effect.  But the extent of the placebo effect with depression is only starting to come to light.  A long and fascinating article in Newsweek lays out the case that if antidepressant medication works, it's only because of the placebo effect.

Antidepressant medication is big business in America, to the tune of $9.6 billion in sales in 2008.  However, research into antidepressants is leading experts to believe we may be buying $9.6 billion of sugar pills - with serious side effects and withdrawal.  

The FDA only approves drugs if they are shown to be more effective than a placebo.  However, as the article points out, "the size of the "more effective" doesn't matter, as long as it's statistically significant."  But the placebo effect creeps into both sides of these studies.

The placebo effect works the other way, too.  If someone in a clinical trial experiences clear side effects, they know they're on the actual drug.  And a surprising number of clinical trial participants (about 80%) are correctly able to guess whether they're taking the actual drug or a placebo.  And, no great surprise, when they guess that they are on the actual medicine, their patient experience is tremendously improved.  Thus, the placebo effect is able to creep its way into the trial results, even when everything is performed to the highest double-blind study standards.

At the same time, many researchers are losing faith in the underpinnings of our understanding of the chemistry of depression.  It has long been a given that depression is caused by reduced serotonin levels in the brain.  Raise the serotonin levels, and you fix the depression.  Except that the research behind this is relatively antiquated, and a new drug trial in France is just as effective as alleviating depression - and it works by LOWERING serotonin.  Obviously, things are more complicated than we thought.

The damning evidence is mounting.  In one study, patients who didn't respond to their initial dosage of antidepressants were prescribed a higher dosage.  72% reported that the higher dosage corrected the problem.  However, only half the patients in the study were actually given a higher dosage - the other half were kept at the same dosage.  Magically it worked better for them when they believed their dosage had been increased.

Doctors are the ones prescribing them, and seeing the proof that they work.  But doctors never prescribe placebos, and so aren't able to see how well those work as well.  And doctors are under pressure to prescribe treatment (just look at our national abuse of antibiotics for viral infections).  As a doctor, if you knew that antidepressants only work via the placebo effect - but that they did work, even if not the way intended - would you continue to prescribe them to patients?

However, there is some good news for depression sufferers.  All of these debunking studies have shown that good old-fashioned therapy is far more effective in treating depression than placebo.  It isn't as easy or as affordable as taking an SSRI, but it does work.