There is an extensive research literature on the effectiveness of various interventions for changing health behaviors, such as dietary habits, physical activity, and smoking. Existing reviews and overviews tend to aggregate research on the effects of specific interventions on particular health behaviors. This review provides a largely qualitative, non-statistical summary of the evidence for the effectiveness of intervention types across health behaviors, by aggregating 706 research items (mostly systematic reviews and meta-analyses) based on the strength of evidence. This review makes a number of subjective judgment calls and uses novel methods of evaluation in order to quickly digest and summarize an extremely large evidence base. It focuses on applications to the farmed animal movement, especially to the behavioral change of reducing animal product consumption. In general, while the health behavior literature includes a very large number of studies, there is much inconsistency in wording, methodology, and subject matter, which makes it difficult to extract useful insights for behavior change advocates. However, some conclusions are warranted. Key findings include that almost all types of health behavior interventions targeted at individuals or small groups seem likely to have effect sizes conventionally interpreted as “small” or “very small,” that their effect sizes tend to be even smaller in the long term, and that interventions with educational and behavioral components outperform solely educational interventions.
See the full post here. (Shared as a linkpost because the bulk of the report is a large tables I thought might be difficult to reformat for the Forum)
To clarify, I suspect we have some agreement on (social movement) case studies: I do think they can provide evidence towards causation—literally that one should update their subjective Bayesian beliefs about causation based on social movement case studies. However, at least to my understanding of the current methods, they cannot provide causal identification, thus vastly limiting the magnitude of that update. (In my mind, to probably <10%.)
What I'm struggling to understand fundamentally is your conception of the quality of evidence. If you find the quality of evidence of the health behavior literature low, how does that compare to the quality of evidence of SI's social movement case studies? One intuition pump might be that the health behavior literature undoubtedly contains scores of cross-sectional studies, which themselves could be construed as each containing hundreds of case studies, and these cross-sectional studies are still regarded as much weaker evidence than the scores of RCTs in the health behavior literature. So where then must a single case study lie?
For what it's worth, in reflecting on an update which is fundamentally about how to make causal inferences, it seems like being unfamiliar with common tools for causal inference (eg, instrumental variables) warrants updating towards an uninformed prior. I'm not sure if they'll restore your confidence, but I'd be interested to hear.