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

[Michael Dewey]

Dear Karen

I will leave it to others to coment on model choice but one thing which 
occurs to me is that if you just use one arm in a trial does that not 
convert it into an observational study?

Michael

On 05/11/2023 10:15, PARRA DE LA ROSA, KAREN via R-sig-meta-analysis wrote:
> 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
> 
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-- 
Michael