[R-meta] Meta-analysis with observational and experimental studies

[PARRA DE LA ROSA, KAREN]

Hi everyone,

I am conducting a systematic review and meta-analysis on the impact of
different types of appearance-focused social media activities on body
image. I wanted to test a novel categorization of these types of
social media activities so we can better understand if the shared
characteristics of different activities could explain their
effect/relationship with body image. On the other hand, I am also
interested in having an estimate per activity. The dataset has 130
studies, half observational (cross-sectional, longitudinal, experience
sampling), and half experimental studies. The vast majority of them
contribute more than one effect size because of different activities
and multiple outcomes. This is my first meta-analysis and also my
first time using R so I have many questions regarding how to specify
the model.

I have read that observational and experimental research cannot be
synthesized in the same meta-analysis as they are answering different
questions. So I was running two different analyses for each type of
study. As for observational studies I fitted with metafor and
clubsandwich a correlated and hierarchical model with robust variance
estimation to account for the multiple dependencies among effect
sizes. So effect sizes are nested within studies. However, the problem
I am facing is with experimental studies. I have organized them in a
different file with the mean, sd, and n per treatment condition. I am
not interested in the comparison with control groups, rather I am
interested in understanding if, for instance, exposure to body ideals
is better/worse than posting this type of content. I have several
comparisons like the one in the example. I thought that a network
meta-analysis in netmeta could be the best solution but as far as I
know, this package does not allow for moderator analysis, so could not
be able to run a subgroup analysis with the categories of activities.
I do not know what the best approach to analyze this data. Also, I
have never seen in my field a paper with two different types of
meta-analysis: a three-level for observational and an NMA for
experimental.

Hope someone on the mailing list could help me with some of this doubt.

Thanks in advance for your help and guidance.

Best,

Karen