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ChristianKl comments on Systemic review of antidepressants vs placebo commentary - Less Wrong Discussion

0 Post author: michael_b 03 June 2015 12:40PM

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Comment author: ChristianKl 03 June 2015 01:13:01PM 2 points [-]

This paper includes an interesting paragraph:

And noticing one of the listed side effects, would you not conclude that you had been given the real drug? In one study, 89% of the patients in the drug group correctly ‘‘guessed’’ that they had been given the real antidepressant, a result that is very unlikely to be due to chance

If that's true shouldn't we ask this question by default in placebo-blind trials?

Comment author: gwern 03 June 2015 06:37:44PM 0 points [-]

Probably but the use and interpretation of blinding indexes is still a bit controversial. For example, the 2001 CONSORT guidelines suggested using and reporting a blinding index but the latest 2010 version dropped it, saying:

Item 11 (blinding)—We added the specification of how blinding was done and, if relevant, a description of the similarity of interventions and procedures. We also eliminated text on “how the success of blinding (masking) was assessed” because of a lack of empirical evidence supporting the practice, as well as theoretical concerns about the validity of any such assessment (23, 24).

Comment author: OrphanWilde 03 June 2015 01:24:33PM 0 points [-]

The absence of the percentage of people on placebos who guessed that they had been given the real antidepressants suggests cherry-picking. Cherry-picking suggests the entire article is garbage.

Unfortunately the article they cite is behind a paywall, but the abstract includes this: "We studied medication guesses of 137 depressed patients and/or their doctors at the end of a 6-week randomized trial of placebo, imipramine, and phenelzine. Overall, 78% of the patients and 87% of the doctors correctly distinguished between placebo and active medication"

Assuming 1/3 were assigned to each group, and the majority of each group guessed they were on medications, the patient percentages are pretty close to what you'd expect anyways.

Comment author: ChristianKl 03 June 2015 01:44:59PM 2 points [-]

From the paper:

Percent correct was 87% (34/39) for imipramine, 96% (22/ 24) for phenelzine, and 59% (22/ 37) for placebo.

Comment author: OrphanWilde 03 June 2015 02:27:54PM 0 points [-]

That's more useful information.

That's significant at a 99% interval with a two-tailed test, so that's significant as far as I'm concerned. (I kept misreading that, and my first three or four calculations with that were assuming 22/37 placebo tests were guessing "Antidepressant" instead of "placebo", so it took an inordinate amount of time to get there. Did the same thing reading the abstract, actually. Teach me to read more carefully.)

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