To help narrow your search to articles that focus on your topic, you may need to limit your search to only look for your health topic in limited fields like Title, Abstract or Title/Abstract (PubMed lets you search both fields at once).
Search Term Connectors:
Focusing on certain types of articles or articles that include specific methodologies can sometimes help with your topic research. Below are some suggestions. (NOTE: You do not want to include all of these at once, or you will likely get 0 results.)
A good tip when researching is to look at the reference section of sources you find useful. Systematic Review and Meta-Analysis articles are particularly good for mining references. This may help aid your research by directing you to new and applicable sources you may not have found otherwise.