[R-meta] Meta-analysis Hedges g - comparisons with same placebo
ruecker at imbi.uni-freiburg.de
Wed Oct 18 10:40:35 CEST 2017
it is a network meta-analysis what you are planning? Do you think of
multi-arm studies including a placebo group? If so, and if it is the
same placebo that is compared to several antidepressants, then I think
there is no problem. The different placebo groups in different studies
provide independent information and network meta-analysis may in fact
increase precision (provided you have loops in your network), but this
is exactly what network meta-analysis is intended to do.
To avoid misunderstandings: What you should not do is to use a placebo
group in a multi-arm study twice in a pairwise meta-analysis without
For an introduction, see
Dr. rer. nat. Gerta Rücker, Dipl.-Math.
Medical Faculty and Medical Center - University of Freiburg
Institute for Medical Biometry and Statistics
Stefan-Meier-Strasse 26, D-79104 Freiburg, Germany
Phone +49 (0)761 2036673
Fax +49 (0)761 2036680
Mailruecker at imbi.uni-freiburg.de
Am 18.10.2017 um 08:12 schrieb P. Roberto Bakker:
> We are conducting a meta-analysis of RCTs between antidepressants and placebo and calculate Hedges g.
> How can we deal with studies which compare different antidepressants with the same placebo? Our concern is when we include the different antidepressant comparisons with the same placebo in the meta-analysis the placebo size will increase artificially which will lead to more precise spurious results. If our reasoning is correct, how can we deal this?
> Thank you in advance,
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