Both The Cumulative Index to Nursing and Allied Health Literature (CINAHL) & PsycInfo databases, feature a Peer Reviewed subset. You can limit your search from the main search screen by checking the "Peer Review" box.
If you forget to limit your search up front, you can limit your search to peer review after the fact. From the Search History/Alerts menu beneath the main search box, click on "edit." A pop up window will display where you can check "peer review."