Is the media distorting findings about antidepressant effectiveness?

Adrian Preda in a rapid response to the debate about whether antidepressants are over-prescribed, which I have mentioned previously (eg. see post), makes reference to his blog entry that blames the media for distorting findings and misleading patients. He makes clear that he is worried that depressed patients may not take antidepressant medication.

I think it is clear that Irving Kirsch is making the case that antidepressants are amplified placebos (see previous post). Preda doesn't really deal with this issue. As I keep saying, there doesn't seem to be any argument that the drug placebo difference in clinical trials is small. The question is whether it can be explained by expectancy effects through unblinding in clinical trials.

The challenge of reducing and stopping antidepressants

In a rapid response to the BMJ debate I mentioned in my previous post, Philip Gaskell has highlighted the problem of discontinuation of antidepressants. His clinical experience is that "the suggestion that they [patients] might move to stopping such tablets is greeted with fear and resistance". 

I have focused on antidepressant discontinuation problems since my original BMJ letter and the development of my antidepressant discontinuation reactions webpage. The issue continues to create debate on this blog and the Royal College of Psychiatrists has already produced the results of its survey to which Gaskell refers (see previous post).

Lies, damned lies and statistics of antidepressant effectiveness

The BMJ has published a head-to-head about whether antidepressants are overprescribed, with Des Spence saying Yes and Ian Reid saying No. Reid quotes the study by Fountoulakis & Möller (2011) that provided a re-analysis and re-interpretation of the Kirsch data, which I have mentioned previously (eg. see post). Reid concludes, "Sadly, demonstrations of methodological flaws and selective reporting suggest that the conclusions [of Kirsch] were 'unjustified.'"

What Reid doesn't quote is the response by Kirsch et al (2012) which shows that the original calculations were in fact correct. The discrepancy comes from using different statistical techniques, the effect of which is that the analysis by Fountoulakis & Möller treats individual studies as though they are equivalently powered. This is contrary to the standard meta-analytic technique of weighting studies with a large sample size more than the ones with a small sample size.

Let's not get too hung up about the statistics! What is significant is that Reid uses a discrepancy like this to try and undermine Kirsch's conclusion. The fact is that the effect size in antidepressant trials is much smaller than is commonly assumed. Not everyone responds to antidepressants even in the clinical trials. It is possible that the small effect size could be explained by expectancy effects introduced through unblinding (eg. see the article by Jo Moncrieff and myself).

Event for psychiatrists

Following the special article in the British Journal of Psychiatry (see previous post),  the Critical Psychiatry Network has organised a day at the University of  Nottingham on 15th April 2013 (see provisional programme).