I'm making a meta-analysis for AEs (adverse effects) related to a drug.
Most of studies are reporting the AE (Depression) and (Anxiety) alone as 2 separate variables but one study is combining them (Depression and Anxiety) together. So we have (1)Anxiety alone, (2)Depression alone, (3)Both (Anxiety and Depression).
Hi,
It was hypothesised that a positive relationship exists between anxiety disorders and cannabis use (particularly with cannabis use disorders) based on the positive relationships between particularly heavy cannabis use and other psychiatric diagnoses (such as psychosis and depression). We expected that some evidence for the direction of such a relationship could emerge from the analysis of prospective studies.
Specifically, we could establish which baseline condition (anxiety or cannabis use) would be related to higher odds of the other condition at follow-up. Furthermore, it was expected that the association between anxiety and cannabis use (or cannabis use disorders) would be lower (or even absent) in studies with effect sizes adjusted for confounding factors, such as other substance use, other psychiatric comorbidity, and demographics (age, gender), compared to studies with unadjusted effect sizes.
Finally, it cannot be ruled out that the use of more advanced quantitative models to establish prevalence of comorbid conditions had some influence on the effect sizes reported in primary studies over time. Thus, we expected that there would be a negative relationship between effect sizes and the date of publication of studies (regardless of when the data were collected). Specifically, we hypothesised that the effect sizes would be adjusted for more factors using more complex statistical models (and thus be lower) in the newer than in the older studies.
All the best.
Ahmed. If I understand your problem correctly you probably need to treat this outcome separately. The only alternative I can see is to combine it with one or the other groups of studies, but not both (because you would, in effect) be counting it twice). There might be approaches whereby you reduce (halve) the weight associated with the study in the meta-analysis and so 'share' the information between two analyses.
Neither of these seem quite right to me though as what is measured in one study is NOT a rate of anxiety nor is it a rate of depression and so adding it to these meta-analyses undermines your definition of variables. Better I think would be perform two meta-analyses and report this study on it's own. In considering the results of the two meta-analyses you can identify whether the omission of relevant information from this single study was likely to alter your result.
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