Because academics and primary consumers of these studies understand their uses and limitations. Not all science has to be groundbreaking new discoveries, simply trying to replicate an existing study or exact same methodology on different cohort is perfectly fine.

The problem is when it gets printed in mainstream press who sensationalize and then posted to reddit/hn where people go 'duh this is obvious, this is a dumb thing to study', 'sample too small', 'not controlling for income/confounding'.

One answer: anyone can start a journal, there are no laws or standards. Peer reviewers are busy and don't always have the background to criticize every aspect of a paper.

Another: not all research can or should have randomized studies (like it just wouldn't make sense if you were, say, determining the structure of a protein). So drawing the line as to what does and doesn't need a specific approach is blurry, and really, can only be enforced during the peer review process, or by the editor.

On the other hand, this kind of work can still serve as a hypothesis generator. Someone else will read this, think, "well they did this all wrong!" and perform a better study that clearly demonstrates whether it has an effect or not.

I guess it's ok to publish uninteresting and probably false things. This could be a fairly accurate description of biomedical science to be honest. It's annoying when it ends up on HN for example, or in the health section of a tabloid newspaper.

In theory, these observational findings could suggest treatments that should be evaluated in a randomised trial. I am not actually sure this is true however, it is possible they are less useful than selecting interventions for further testing in some other way. Anecdotally, folk remedies may have a higher hit rate for selecting treatments for proper evaluation. This is often surprising - eg a precursor to aspirin is found in the Willow tree, which has been used as a medicine for thousands of years. Another example is the foxglove plant from which the heart drug digoxin is derived, which was used as a herbal medicine predating modern medicine.

> The real question is: why is anything other than randomised studies allowed to be published in the first place?

Because things other than randomized studies produce the results that generate the funding for randomized studies.

Not questioning the need for RCTs, but they have their own issues. Like, let's say you do a RCT and it shows an effect, but then in a large epi observational study there isn't any? There would be some problems to work out.

RCTs are great but can have problems with generalizability to real-world conditions. Ideally you'd study both.

Observational studies are far cheaper and easier, and are actually very useful for a lot of situations.

This is a good point. I was recently having a conversation with a non-scientist (I am not one either) about two different studies. One was an RCT that found no effect for a treatment, and the other was a "case control, test-negative" design study that found a beneficial effect. My friend said the latter was as good as an RCT because it also has a control arm.

But when I looked up what "case control, test-negative" means, I found that it is observational, and there is no intervention provided to any of the individuals. Some of the recent discussions of the design indicate that it is understood by scientists, but can mislead laypeople, who assume that its conclusions are much more robust than they actually are.

We should definitely continue to do research of many types, partly as a way to figure out where to spend the time/money to do RCTs (which are more expensive than other types of analysis). But we need people reporting on studies to be very clear up-front when they are not describing an RCT. They should say what the study's conclusion means, versus what it would mean if there were a similar 'finding' in an RCT. Otherwise people will not understand that they are being told a weak conclusion, not realizing there is a strong conclusion that has gone unmentioned.

Published, or publicized?

All science needs to be published. Pilot studies, observational studies, quasi-experimental studies. Otherwise, we don't have the information we need to create randomized control trials.

However, I'd strongly support keeping all that science from being publicized.

You can't do randomized studies for things like nutrition if the question is "does eating red meat for a decade increase the risk of cancer". Nobody's going to comply with it.

Not everything can be done with a randomized controlled study. For some fields (quantum mechanics, volcanology, climate change, paleontology...) most studies can't be randomized, much less blind. This is also true of longitudinal studies: you can't fully control anyone's exercise and diet over months, much less decades.

Yet we want to do research in these areas. So we have to make do with what's possible.

With all the common sense replies explaining why, I guess this was not the real question at all.