Neuroskeptic: Take Your Placebos, Or Die →

In the placebo group of 1174 patients, the people who took all of their placebo pills on time (the good adherers), were significantly less likely to die than the patients who missed lots of doses. People who took over 75% as directed were 40% less likely to die than those with less than 75% adherence:

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But what’s remarkable is that when the authors corrected the statistics for all the confounding variables they measured - including things like age, gender, ethnicity, smoking, body mass index and blood pressure - it barely changed the effect. Some of the factors did correlate with adherence, but not in a way that it could explain the adherence effect on mortality.

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What the placebo adherence effect demonstrates is that there may be confounds no-one has thought of. They might even be impossible to measure. And if these mystery confounds can literally kill you, they can probably cause all kinds of other effects too.