Consider typing "community psychology" (in quotes) to indicate that you need articles with that specific phrase.
Use each database's thesaurus or subject headings list to identify the best wording for your topic. For example, PsycINFO uses:
- Community Mental Health Services
- Community Services
- Early Intervention
- Deinstitutionalization
- Mental Health Programs
- Outreach Programs
- Primary Mental Health Prevention
- and many other words to describe various topics within "Community Psychology"