80% of Prozac Power is Placebo

80% of people’s improvement after taking drugs like Prozac was exactly the same as if they took a sugar pill.

Placebo is Latin for “I shall please”.

I came across this incredible demonstration of the placebo effect in Kirsch et al., (2008), reviewing results from 35 clinical trials of modern antidepressant medication (things like Prozac):

“The response to placebo in these trials was exceptionally large, duplicating more than 80% of the improvement observed in the drug groups. In contrast, the effect of placebo on pain is estimated to be about 50% of the response to pain medication.”

In other words 80% of people’s improvement after taking drugs like Prozac was exactly the same as if they took a sugar pill. Pain pills, on the other hand, do more over and above the placebo.

And antidepressants didn’t even really work for severely depressed people:

“The difference in improvement between the antidepressant and placebo reached clinical significance, however, in [..] severely depressed patients […] the apparent clinical effectiveness of the antidepressants […] reflected a decreased responsiveness to placebo rather than an increased responsiveness to antidepressants.”

So, for the severely depressed antidepressants seemed more effective because the placebo didn’t work so well.

It’s a dilemma because the pills are doing something, but what? Is it just the effect of believing they will help you? Does it matter how much you believe? Is it the fact that you get them from a doctor who tells you they will help?

Quite apart from the whole debate about the prescription of antidepressant medication, it really shows the amazing power of our beliefs on how we feel.

Image credit: Christin

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Hello, and welcome to PsyBlog. Thanks for dropping by.

This site is all about scientific research into how the mind works.

It’s mostly written by psychologist and author, Dr Jeremy Dean.

I try to dig up fascinating studies that tell us something about what it means to be human.

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Author: Jeremy Dean

Psychologist, Jeremy Dean, PhD is the founder and author of PsyBlog. He holds a doctorate in psychology from University College London and two other advanced degrees in psychology. He has been writing about scientific research on PsyBlog since 2004. He is also the author of the book "Making Habits, Breaking Habits" (Da Capo, 2013) and several ebooks.