Find the Publication Type in the lower right and select, Reports- Research
1). In PsycInfo, click advanced search.
2) Under Methodology, use the CTRL key (PC) | Command key (MAC) while clicking your mouse to select the following: Clinical Trial, Empirical Study, and Treatment Outcome.
Since these are published in Scholarly Journals, limit to Academic, Scholarly, or Peer reviewed articles.
Then try adding this boolean phrase to your search empirical or study or studies.
This will help limit your results but does not guarantee that all articles will be empirical studies.