Why did we think otherwise? Why did we think Prozac, say, was a wonder drug, when in fact it has very little antidepressant effect? Why did people think it changed them?
The simple answer is bias. Biased studies, produced by biased researchers, published in biased journals, reviewed by biased editors and reviewers. Bias is very difficult to eliminate. In this case the drugs were very expensive to develop and test. So the temptation to exaggerate the effect was enormous. This was mainly done by not reporting studies that showed no or negative effects. But some of the studies were poorly designed and also allowed bias to creep in. Whether this was deliberate or unconscious is another matter. The fact is that bias was an important factor in the science of these drugs.
And this was backed up by the usual media hysteria about wonder-drugs. The media are a particularly pernicious element in this situation. Even more than the big pharmaceutical companies they are invested in bias. News media bias is towards any story that will provoke strong emotions, especially anger, disgust, fear, or lust. And if a promising story doesn't quite make the grade it can easily be sensationalised so that it does the job. Prozac became a sensation for precisely this reason. A lot of false information about "happy pills" circulated and the general public became thoroughly misinformed on the subject of antidepressants.
And because of the bad science and the media hype the people prescribing these drugs were already biased when they started dishing them out and this meant they were more likely to focus on apparent successes and less likely to even see apparent failures. Many people prescribed the drug were not really depressed. So a bit of placebo was all they needed to feel better.
All this adds up to a massive misunderstanding. We had to wait for a whole new generation of scientists to be hatched and start questioning the orthodoxy. Which is what is happening now.
I used to be a firm believer. I bought the chemical imbalance narrative of depression and the drug treatment option. I took various drugs for decades. But they didn't really work. I still got depressed. I still got suicidal (despite being on two antidepressants). It's facetious, but there is some truth to the quip:
"Before you diagnose yourself with depression, check you are not surrounded by arseholes."Although I have some underlying pathology, the usual trigger for my depression is situational, and especially to do with conflicts in my living situation. Depression is an adaptive response to our environment. For example if it is triggered by hyper-stimulation, we may become aversive to sensory stimulation or find ourselves responding with anger to everything. Because of the distorting effect that psychoanalysis has had on our intellectual landscape we don't look for situation causes, we only look for individual psychological causes. But this is almost always a mistake. Environment, and especially social environment, is always a factor in mental illness. It is not always the immediate or necessary cause, but it is always a factor. In my case it has frequently been causal and it accounts for the underlying pathology.
So the whole long experiment with these drugs has been a misunderstanding based on bias and misinformation.
This raises the question that if ADs don't work, is there an moral argument for, say, homoeopathy? The homoeopath gives a null-treatment, delivered with conviction in a semi-ritualised context to cultivate belief. That belief in the treatment generates the placebo effect which results in a real increase in well-being!
BTW if you are taking antidepressants and this news tempts you to stop taking them, please do so gradually. Suddenly stopping them can have very unpleasant withdrawal effects. Taper off doses gradually. And let people know, because it will most likely be disturbing.