Here are some possible solutions:

• Standard vs. All Words search: Remember from the Basic Search section that the default Standard Search looks for words as a phrase. Switch the search to an All Words search to find articles with all the keywords in any order (not just a phrase).
• Use a root word followed by an asterisk "*": To search for variations on a word type the root word then "*". Example: teen* will find: teen, teens, teenager, teenagers, etc.
  
  
• Use alternative keywords: It may be that the articles use different keywords to describe the concept you are searching for (such as adolescent rather than teen). Even if PsycINFO only finds a few articles look at their titles and abstracts (summaries of the article) to see if there are other search terms you could use or try to think of some yourself.