Here is an example of the subject terms listed for a systematic review found in PsycINFO, "Primary care screening for and treatment of depression in pregnant and postpartum women: Evidence report and systematic review for the US Preventive Services Task Force" (2016).
The controlled vocabulary system for PubMed is MeSH: Medical Subject Headings. Using MeSH in combination with keywords is the most effective way to search PubMed.
For example, here are some MeSH terms for:
Adults: Adult (A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available.)
Screening: Mass Screening (Organized periodic procedures performed on large groups of people for the purpose of detecting disease.)
Search using MeSH from the National Library of Medicine in the PubMed database: