Is this peer reviewed?

The student group who have to justify their choice of database (see separate post "Why use that database?" for discussion of that) also have to choose a peer reviewed paper to appraise.

How do you know?

Here are some ideas.

Cinahl has a limit for "peer reviewed journals".    PubMed does not.    But I think a peer reviewed journal (like the BMJ) might publish pieces that are not peer reviewed (like editorials or letters).

Perhaps you can assume that research, review and systematic review articles in a peer reviewed journal have been peer reviewed.   But I think you would need to check the journal's own policies, on the journal website, to see what process articles go through.

You can certainly assume that a preprint, something from somewhere like medRxiv, has not been peer reviewed.   Preprints like that are appearing now in PubMed, but it is clear when you reach the full text that it has not yet been peer reviewed.

What else can you do?

You could check the database policies - does it only include peer reviewed articles or journals?   It would explain PubMed's lack of "peer reviewed journal" filter, if PubMed only included peer reviewed journals, but but PubMed itself does not say either way and so I would not assume anything.   Also, it does include BMJ editorials and correspondence to journals, so actually we know that not every item in PubMed has been peer reviewed.

I wondered if the list of journals indexed in Medline says if a journal is peer reviewed.   It does not, as far as I can tell.   

Perhaps the article itself will tell you?   If it shows dates when it was accepted, modified, and published, it tells you the article has been through a process, but it does not tell you what the process is.

You can, as alluded to above, check the journal itself.   Can you tell from the journal website (and I would hope you can) if it has a peer review process, and if it does, what it is, and what article types it applies to?    

I hope that helps, at least a bit!