Some databases, such as Ovid MEDLINE(R) ALL, include many thousands of non-indexed records and pre-print publications. These new records flood in from electronic publications and there is a time lag before they can be fully indexed or described. The records received from publishers are basic and don't (yet) include subject headings. Of course these non-indexed records include the latest research, so we don't want to lose them.
There are the only two limits we recommend:
Don't 'limit to humans'
If you select 'limit to humans' you risk losing all non-indexed and pre-print publications in a database which have not been indexed as 'human'. This could be thousands of records.
Instead, remove the animal studies
A safer alternative is to search for the things we don't want (in this case animal studies) and remove them from the results. Adjust the line numbers below as appropriate.
Ovid Medline
6. [last line of search - your line number will be different]
7. exp animals/ not humans/
8. 6 not 7
Ovid Embase and Ovid Emcare
6. [last line of search - your line number will be different]
7. exp animal/ not human/
8. 6 not 7
APA PsycINFO (Ovid)
6. [last line of search - your line number will be different]
7. (animal not human).po.
8. 6 not 7
CINAHL (EBSCOhost)
S6. [last line of search - your line number will be different]
S7. (MH "Animals+") NOT (MH "Human")
S8. S6 NOT S7